Air conditioner, air cooler, dehumidifier or fan – What works?

Before I start, I’m not selling or advertising anything here.  There isn’t an affiliate link or banner on my website. 😉

Despite all the rain here in Ireland, it does get warm from time to time, often to the point where it is difficult to sleep at night.  However, what is more surprising is that I see people using air coolers that can actually make their environment even worse, not realising how these operate!  So in this basic guide, I’ll go through the types of appliances and where they work best and why air coolers are not really useful in the Irish climate.

Temperature & humidity

High humidityEveryone knows that it is uncomfortable working in a warm or sticky room, but what they may not realise is that it is not just the temperature that affects how bad it feels.  The humidity plays a major role also, just like the great outdoors.

Before you purchase an appliance for trying to control the temperature/comfort, it is well worth purchasing a hygrometer first, which will show the room’s temperature and relative humidity.  Ideally, the room should be between 20C and 22C (18C for a bedroom) with a relative humidity of 40% to 60%.

In this example to the right, a hygrometer was placed in a room where I felt quite sticky.  As the hygrometer shows, the temperature is ideal, but the relative humidity is very high.  In Ireland, it is quite common to see the humidity exceed 70% indoors in the summer.  In this example the weather was warm, hazy and humid outside.

How to control the room comfort

Once we establish what the temperature and relative humidity is, if either reading is outside of the ideal range, it is time to control it.  This is where we choose an appliance.  From here, I’ll start with the cheapest to the most expensive and explain how each is used and when to use or not use them!

Open a window!

Not really a surprise as the first tip. 😉  In many cases, simply opening a window is enough to cool the room or make it less sticky, even if it is warm outside.  Like I mentioned above, it is not always the air temperature that makes the difference, but the lower outdoor humidity.  Of course, this may not be an option in all cases such as if it is noisy outside, too windy or if there is no window to open.

Fan (Desk, floor-standing, etc.)

It is not really a surprise that most people use a fan to keep cool, especially since it is very effective and cheap to get hold of.  A light breeze in the room typically gives the feeling of the temperature being around 2C cooler than it actually is.  They also boost the effectiveness of air conditioning, for example, if an air conditioner cools the air by 5C, a blowing fan can give the impression that the room is actually 7C cooler than it was.

Air Cooler (no vent hose or outdoor unit)

An air cooler works by evaporating water to cool the air, since as heat energy is absorbed doing so, this lowers the air temperature.  As a result, a portable air cooler requires water to operate and some models recommend adding ice for better effectiveness.  The catch is that as they add significant humidity to the air.

Unfortunately, many people assume that as they don’t have a vent, they don’t need a window open!  So what happens if an air cooler is operated with all the windows closed?  Assuming the relative humidity is reasonable to start off, when the air cooler is switched on, it will do its job for a short while.  Once the humidity rises up towards saturation point (around 80% RH), the cooling effect stops.  With the cooling effect stopped, the temperature will gradually rise up to where it started and the room will end up feeling warm & sticky!

With the typical high humidity in Ireland, I do wonder what is the point in selling these at all here, considering how seldom it gets warm with low relative humidity.  Also, as an air cooler reduces a person’s effectiveness to sweat to stay cool, they should not be used in places with intense physical activity such as while working out.  E.g. if you have a home gym, don’t run an air cooler while working out!

Water Cooler (For drinking)

While this is something that does not affect the room temperature, having cool water on tap can make one feel cooler.  This can also be more cost effective than running an air cooler, without its side effects either.

Dehumidifier (Portable unit)

This is an appliance typically used by builders to dry buildings, painted walls and deal with flood damage.  Some people use them to control dampness.  What most people don’t realise is that they are also a very effective way of controlling stickiness, especially when it is not practical to open a window.

Dehumidifiers work by condensing the moisture in the air and collecting it in a container.  From my experience, most small dehumidifiers collect 2 to 4 litres per day with a room temperature of 20C and relative humidity of 60% to 70%.  The only catch is that if the room is very humid (e.g. over 70%), it can warm up the room, however, personally I prefer feeling warm than sticky & sweaty.  Once the room humidity drops, the dehumidifier will operate less and the temperature will return back to what it was, so ideally they should be run throughout the day for the best effect.

In the above photo example of the high humidity reading where the room was 20C and 79% relative humidity, this is where a dehumidifier works well.  With a dehumidifier in this room, the temperature climbs by around 2C and the humidity level falls by around 15% to 20% after an hour of operation.  After the second hour, the temperature falls back around 1C while the humidity stays around 60% to 65%, leaving the room feeling a lot more comfortable.

The catch with a dehumidifier is that it requires the windows to be closed to be effective.  They are also less effective at controlling comfort in high indoor temperatures such as above 25C.

Finally, don’t try running a dehumidifier and air cooler together in the same area!  First of all, most air-coolers can evaporate up to 1 litre an hour, which will overwhelm most dehumidifiers.  Also, as I mentioned above, a dehumidifier releases heat energy when it condenses the moisture in the air, while an air cooler absorbs heat by evaporating water, so by running both together, this will have the effect of a complicated space heater as the room will warm up from the energy used to run both appliances, much like leaving a refrigerator door open to try cooling a room. 😉

Air conditioner (Vented portable unit)

Unlike an air cooler, an air conditioner lowers the humidity instead of raising it.  This means that besides the air feeling cooler, it also eliminates the stickiness.  Most air conditioners have two modes of operation – “Dehumidify” and “Cool”.

In the cool mode, the air conditioner lowers both the temperature and the humidity.  This relative humidity will stop declining once the amount being extracted reaches the amount coming in the air coming in the room to replace what air has been vented out.  The temperature however will continue falling for an hour or two before it bottoms out, sooner if there is a significant breeze coming in the Window opened for the vent hose.

In the dehumidify mode, the air conditioner condenses the moisture in the air like a dedicated dehumidifier, but instead of collecting it, it evaporates it out the vent along with the heat produced by its compressor.  This has the advantage of lowering the room’s humidity quickly without raising the temperature, unlike what a standalone dehumidifier would.  The catch is that as a window needs to be open for the vent, it costs more to run and is impractical as a dehumidifier to control dampness.

For anyone interested in running an air cooler with an air conditioner, this is one case where it will likely have some effect, since as the air conditioner extracts humidity as well as dumping the heat released from condensation outdoors, an air cooler have an effect.  However, the efficiency of the air conditioner will be reduced as it will be using more energy to condense water than cooling the air, so while an air cooler may help bring cooler air to a specific area, it will likely reduce how cool the air the air conditioner puts out.

81 thoughts on “Air conditioner, air cooler, dehumidifier or fan – What works?”

  1. Hi Sean,

    I was planning to run Dehumidifier and room cooler together AND THEN,
    I found your post !

    Thanks for the info… you saved my money

  2. Hi Sean,

    A question, what could the best possible way to cool and remove humidity from a closed room with no windows ?
    (my apologies if this seems just too demanding)


    1. Unfortunately, there is no straight forward way that I’m aware of, at least without involving the outside. The alternatives would be either resorting on a good fan and a drinking ice cold water. At my workplace, that’s generally what I do. But then again, it’s generally just 2 to 3 weeks a year when the office gets too warm.

      If one or more walls are facing outside and you own the building (or no issue with landlord drilling holes), one option would be to get a portable vented air conditioner, drill a duct in the wall similar to one for a vented tumble dryer and attach its hose to the duct. If there is already an outside vent or duct nearby, you could probably use that to connect the portable air conditioner to, with the help of an extension hose.

      Unfortunately, combining a dehumidifier with an evaporative air cooler is as effective as trying to recharge a battery using a solar panel with a bulb powered by that same battery. Basically, the heat absorbed by the evaporated water will be released by the dehumidifier.

      1. Hi
        Your information is very helpful
        I have a screened in porch that gets very hot and humid even with windows open – here on the east coast where humidity levels can get in the 90s. Do you have any suggestions what to use to get the humidity and temperature down? It’s approx 250 sq feet and not as usable as I would like

      2. Didn’t mention if there are vents in the room, such as return and supply vents. There are units that sit on the return vent using check valves to keep the heat and humidity going in one direction. Essentially they work like a dehumidifier and heat pump together. That alone, if sealed properly will reduce the humidity first, then slowly reduce the heat in the room. It’s harder to change the temperature when you have a humid room, it takes more energy to heat or cool it.

        It’s official name is “air exchange/air exchanger”. There are passive designs that don’t use power but don’t offer that great a difference in RH and temperature, some use power that are far more effective. However, it’s not as effective as an air conditioner but it uses less power than one of those; it’s a trade off.

    2. Get an Air conditioner installed which cools the room with no window. This has dehumidifier as well.

  3. Thanks for posting this Sean. I am in Africa and wanting to buy an air cooler that works with water/ice (portable without vent holes or outdoor unit). It gets quite hot here at times. Can this be a proper solution for me?

    1. If the room’s humidity is fairly low (<50%), they can work quite well, but you still need good ventilation to prevent the humidity building up. Otherwise once the humidity approaches around 80%, the machine will just be blowing humid sticky air about. If you are sitting at a desk such as working at a computer, one option would be to place the air cooler next to you with the output either blowing towards you or under the desk. This way it cools your area without adding as much humidity as trying to cool the whole room.

      An 2kg ice pack will absorb about as much heat as what a 2 litre boiling hotwater bottle will give out. It will probably be effective keeping a small area such as below a desk cool, but certainly not cool a full room much before the ice melts. Just make sure you freeze the ice pack in a freezer located in another room. Like how an air conditioner pumps the heat outside, fridges and freezers work the same way, i.e. they pump the heat into the room, which is why their sides or back get warm while running. So by freezing the ice pack, that heat it 'pumped' out will end up in the room.

  4. i have a portable ac does the cooling when it is on the dehumidifier concern is that why it is not doing the cooling on the cooling mode?and is it safe to run the ac on the dehumidifier mode because main concern of the ac is to get a cool matter what the mode is.only cooling is required.

    1. In Cooling mode, try lowering its temperature dial as low as it goes. On portable units, the minimum is usually 16C (61F). If it is still not cooling, then it probably has a faulty thermostat. In this case I would suggest contacting the shop for a repair or replacement.

      Normally in dehumidify mode, you would disconnect the vent hose and open its drain plug over a drain or large tray so that the warm air stays in the room, while the condensate water is poured away. But by sticking the vent hose out the window in dehumidify mode, it will just operate the same as the cooling mode with the fan set at low, the exception is that it does not switch off at a target temperature like the cooling mode would. So this is a workaround if it’s out of warranty.

      It should be safe as the unit is working the same as the low cooling mode, but without monitoring the temperature. The main thing you will need to watch out for is the running time. As it will run continuously in dehumidify mode and only stop intermittently to defrost its coils, it will quickly run up the electricity bill if run morning to night every day.

  5. Sean I have two room attached can i put Dehumidifier in one room and dry air feed to cooler so cooler will give cold air to next room

    1. Although it’s something I haven’t tried, I would imagine that would work but to a limited extent. Many air coolers I’ve seen are advertised as being able to provide 1000 watts of cooling, which basically translates to the amount of heat absorbed by evaporating water. It takes roughly 0.628kWh of heat to evaporate 1 litre, so this means such an air cooler is evaporating up to about 1.6 litres per hour.

      One problem is that very few domestic dehumidifiers are capable of extracting humidity at that rate. Even with a 30 litre model, the 30 litres refers to 80% RH at 30°C and most only extract 60% their rating at 60% RH at 26°C. So even with a powerful dehumidifier, it will probably only extract at half the rate the air cooler is putting out in the other room.

      Another problem is that as the dehumidifier is continuously removing moisture at such a high rate, it is also releasing all the latent heat that was absorbed in the other room, in addition to the heat from its running compressor, so that room will get very warm after an hour or two of running and the spill over to the other room will not take long to overcome the rate the air cooler is trying to take out.

      A more effective option would be to get a portable vented air conditioner and put the vent hose into the other room. Most portable air conditioners have a drain plug, so you can open the plug and place a pan below it, so this way only heat and not the moisture is being “pumped” into the other room. I have tried this method in the past to cool an upstairs room with skylights while it was raining and it was quite effective. The other unused room obviously got rather warm, but meant I could cool the room I was in without letting the rain in from an open skylight.

  6. I have what I regard as a relatively short term problem but it could be costly. I have about 80 bottles of wine stored in a spare bedroom cupboard and with the rise in temperature, the room is about 4-6 degrees too high. I have opened windows , put in a cold air blower and I might pull back a degree or two. Trouble is there is no place cooler in the house. Can you recommend a cost effective piece of equipment/system that will get me those couple of degrees. I reckon I will only have this problem ever for maybe a 4-6 week window in any year so I do not want to spend a large amount of money.

    1. If you have the space, one potential option would be to get a tall fridge without freezer (e.g. 200 to 250 litre capacity), place the bottles inside and operate it on its minimum setting. You can use a plug-in timer (e.g. 30 minutes twice a day) if you just want to bring down the temperature a little such as to just below 20C.

      The fridge will be far cheaper to run than any air conditioner. For example, a typical 200 litre fridge uses around 0.4kWh per day, which on a typical Irish electric tariff (19c/kWh) works out at €2.30 per month. A portable air conditioner would consume this in just 12 hours of continuous operation.

      Although the weight of let’s say 15 bottles per shelf may seem a lot, most fridges have no problem handling 20kg per shelf such as for the likes of a large stuffed turkey in a crockery pot.

      1. Thanks for that.
        Unfortunately space an issue. I am less concerned about ongoing running costs as I reckon at worst I would only need intervention only over a 6-8 week period and then only for say 1-1.5 hrs X twice a day.
        I will get away with a small [if there is such a thing] air conditioning unit in the spare bedroom for a couple of weeks, but a fridge would be out of the question. Garage space is not available.

        Thanks for taking the time to answer

        1. If you own the house (i.e. no problem drilling holes, etc.), one potential option would be a portable vented air conditioner unit, with a vent hole in the wall (similar to for tumble dryer) for the hose.

          Another potential option would be a wine fridge where you rotate a set of bottles, such as 30 (or what the fridge can hold) in one day, change around with another 30 the next day and so on and surround the stored bottles with insulation (e.g. blankets) so they stay cool longer while waiting for the next batch to chill.

          1. Reckon your reply to Leon might just crack it for me!!!!
            quote ‘……….Another thing worth looking out for is some sort of outside reflective film/cover for the window………’

            The room in which I store the wine is south facing and gets sun all day and I reckon I can get my hands on some foil covered plasterboard and cut it to fit the outside of the window as a temporary shutter that I can put up/take down as required.

            Thanks for that


  7. My bedroom at night gets very stuffy and very warm (even when the outside temperature isn’t particularly hot) and have wanted to buy something other than a fan for a while now but am finding it difficult to decide what to buy. My requirements are that it is quiet, portable and doesn’t give you the sensation when you wake up that you have a cold (or a dry mouth/throat and nose) – you’re help would be much appreciated!

    1. One suggestion would be to look for some sort of outside reflective film/cover for the window. This will reduce the amount of heat from the sun getting into the room during the day. Although closing the curtains may seem like the same thing, the problem here is that the heat is trapped on the inside, so still warms up the room, whereas shading the outside prevents the heat getting to the inside of the glass.

      Off hand, the only unit I can think of would be a split-unit where there is an indoor and outdoor unit, similar to what hotel rooms use. The compressor is what makes the noise in the portable vented units, whereas with a split unit, the compressor is in the outdoor unit so the fan is the only thing audible with the indoor unit. Unfortunately, they are quite expensive, require professional installation and holes to be drilled for the lines, which rules out installation if you’re renting the home.

      A very light duvet for the bed might be also worth trying if you can get hold of something lighter than what you have. Last summer, I was surprised over the difference of changing from one duvet to another. Don’t use any ‘mite/water protection’ type cover over on the duvet.

      If you have a portable vented air conditioner, run it one to two hours with the bedroom door closed so you can switch off the unit before going to bed.

  8. Hi Sean,

    Many thanks for your insightful article. I’m currently subleasing office space and the issue of AC has become quite a problem. After 5:00 PM and on the weekends the landlord sets the temperature to 80F, making the facility basically unusable outside of the standard 9 – 5 shift.

    The solution I’m thinking of is to combine an industrial dehumidifier with a commodity evaporative cooler to balance RH while cooling the office room. You mentioned in your article that this is a Bad Idea, but I’m not sure if you’re aware of the power of newer dehumidifiers.

    For example, this unit can remove up to 70 pints / 33 liters of humidity per hour:

    While this evaporative cooler seems more modest at 500 CFM / 250 sqft rating:

    The room I’m trying to cool is roughly 250 Sqft, and the ambient RH where I’m located in Florida is typically just 50% – 60%.

    Would you still say that I’m grasping at straws here? A backup idea is to combine a dehumidifier set to 45% RH with this portable air conditioner and run the exhaust into the plenum/crawl space above my office suite:

    I’ve read that running the exhaust into the plenum space is a common practice in server environments, but I’m a bit afraid of unintended consequences in doing so.

    Any advice or feedback you could provide would be much appreciated!

    1. I should add that the evaporative cooler would only need to run 4 – 5 hours per day, while the dehumidifier could run 24/7.

    2. The main issue with using a dehumidifier in the same room as an air cooler is that it releases the latent heat from the evaporated water. It takes roughly 2.26MJ of heat to evaporate a litre of water (2.1 pints), so once an evaporative cooler evaporates a 1 litre, it has taken 2.26MJ of heat out of the air. Even with a very energy efficient dehumidifier, by the time it collects a litre of water, it will have released that same 2.26MJ of heat in the process of condensation.

      The portable air conditioner with the exhaust running into the crawl space should work quite well. As heat rises, basically the next floor above you (if any) will get the rejected heat as the heat rises up through their floor. Rather than get a separate dehumidifier, I would suggest getting a portable air conditioner that has a drain port. Like a dehumidifier, air conditioners also condense water out of the air. Portable air conditioners normally evaporate that condensed water out the vent hose. One potential issue here is that concentrated warm humid air going into the crawl space can cause mould growth, rust, watermarks, etc. However, if it has a drain port, you can collect that water in a tray, leaving just warm air going into the crawl space, which shouldn’t cause any issue.

      With a server room, generally those rooms remain unoccupied and closed, which means there is very little humidity getting into the room that would get collected by the air conditioner, so generally there is little risk of it causing mould/damp issues within the crawl space.

  9. Hi Sean, I need to lock up my apartment and move countries for work. I have a fully furnished home with furniture, equipment and appliances. In India, we do have a few storage facilities but these are proving to be expensive as I’ll be away for 3 years. Temperature and ambient RH will keep changing through the year with change in seasons. How do I control heat and humidity without use of electric equipment as I need to switch off mains to avoid electrical hazards per apartment society rules. Any suggestions are desperately sought 🙂 Thanks for reading.

    1. Off hand, the only thing I can think of would be to put the most valuable small items in plastic storage boxes with a 1kg silica gel desiccant pack in each. During damp periods, the desiccant packs will prevent the humidity building up within the storage boxes. If you need to store anything next to an outside wall, leave a gap of at least 15cm or 6″ for air to circulate to avoid mildew build-up.

      For bulky items such as furniture and equipment, I would suggest leaving any drawers slightly open so air can circulate in & out, especially the washing machine and dishwasher. Switch off the water supply to the apartment also as a unexpected leak would lead to a disaster.

  10. Sean, my room has no window,but there is a little opening in the wall serves as a ventillation, I’m just thinking if what appliances would be fitted to my type of room, is it portable ac or anytype of ac OR air cooler, coz its really hot and im about to give birth and i dont want my baby to suffer this kind of hot weather. If air cooler plus exhaust fan, would it be better and not dangerous to my baby?.thanks!

    1. I’m not entirely sure if it’s possible to connect a portable AC to a wall vent as the AC’s vent hose carries a fairly substantial air flow. If it looks like a tumble dryer vent hose can be attached to it, then it probably will work with a portable AC vent hose.

      If the outdoor humidity in your area is typically low (seldom above 50% RH during summer), then the air cooler may be more effective if your room has an exhaust fan. Generally an air cooler is not harmful to run as long as it’s well-maintained and kept clean. The higher room humidity is less likely to be an issue during the summer months as moisture in air will not condense on the the slightly warmer walls. In the winter, humid air results is more of an issue as the opposite is true, i.e. the outside facing walls are cooler than the heated indoor air, so excess humidity will result in condensation forming and in turn the dampness related issues.

  11. hi sean. im planning to buy a portable dehumidifier since it is really dusty in our place and my son is having allergic reactions due to dustmite. my question is, is it still a good idea to use a dehumidifier even if we reach 30-40 degrees celsius everyday (summer season). im afraid it would get even hotter if we use dehumidifier, but i hate sneezing everyday due to dust.
    we only use fan by the way.

  12. Hi, I live in Georgia where the heat/humidity is borderline unbearable. My bedroom gets very humid during summer months and a fan would just circulate warm air it felt like. The house ac system went out last year and prob won’t be repaired anytime soon either. There are 3 windows but they are sliding and small so I couldn’t fit a venting hose kit for portable ac unit nor coukd I put in a window unit. The bedroom is built above a,basement that builds up water whenever it rains snd needs to be pumped out due to a some leak on outside. What would you suggest in this situation?

  13. Hi Seán,
    I’m an Irishman living in Milan, so I’m trying to understand the best way to survive the summer months – when both temperature and humidity become very high. Temperatures can reach 40c, and humidity can sometimes reach upwards of 80% – an uncomfortable combination. Don’t want to invest in proper AC as movimg house next year, so looking for an afforbable method, and portable if possible. I’ve excluded an air cooler from my thinking based on your article…..way too humid an environment to consider it.
    Portable AC has the drawback of having a vent which needs to ne left hanging out a windpw etc. I don’t want to leave a window open during the night (night time is when things really heat up here).
    I was thinking of getting a humidifier to at least tackle the humidity problem, although it will obviously result in higher temperatures. Perhaps I could combine the dehumidifer with a standard fan. The fan should help offset the increased temperature from thr dehumidifier by roughly 2c based on your article.
    Anyway, given the above, do you reckon the dehumidifier + fan would be the best course of action?
    PS great article + comments. I was just about to buy an air cooler on amazon prior to finding your article….thanks for saving me that wasted expense 🙂

    1. Yikes! – What I wrote here was based towards the Irish climate that I live in. Here it often gets very humid, but the temperature generally does not go above 20C often.

      If the indoor temperature is hitting 30C or higher, I don’t think a dehumidifier would help much. The higher the temperature, the more humidity the air holds and in turn the more a dehumidifier would need to collect to bring down the percentage. The more water vapour condensed to water, the more latent heat given off, so the temperature rise could be more like 5C. Some dehumidifiers will not operate above 30C, i.e. go into overheat cut-out.

      In this case I can’t think of any quick fix as I’ve never dealt with that time of climate. The ideal method would be to get a split AC system installed, but if you’re in a rented flat, this probably is not an option, not to mention the overall cost. Two possible options I can think of would be either a combination portable dehumidifier/AC or a portable split system.

      There are a few combination portable dehumidifier/ACs available that work like a vented portable AC, but which can also function as a dehumidifier without the vent hose attached. This way you could run it as a dehumidifier when it’s just humid and attach the vent hose out the window to bring down the room temperature. These are priced similar to a dedicated portable AC.

      If you’re on the ground floor or have an outdoor area, another potential option would be a portable split system (e.g. Trotec PAC 4600). These work like the professionally installed split systems with advantage that the indoor and outdoor units are portable, i.e. no installation. The outdoor unit is linked to the inside unit with a pipe, so the window only needs to be opened slightly for the pipe, which I think is no wider than a garden hose. Unlike a vented AC, the advantage here is there is no outside air coming back in replace what was vented out, so the room cools down further. Unfortunately, they are quite expensive, typically over €1,000.

      1. Thanks Seán for the quick response. Yeah, reckon the portable AC is the only way to go….that or an ice bath!
        The Pinguino by De Longhi seems to be the portable AC of choice here so will look into one of them.
        Thanks again for the helpful article/response…should help make it a more “comfortable” summer!

  14. Hi Sean
    I am in Ireland as well and run a wildlife hospital. We have 2 buildings and cant leave windows open for obvious reasons (wildlife we want to stay in can get out and wildlife we want to stay out can get it!) We need a inexpensive way to cool the building (18ft by 8ft) down, keep the humidity to a minimum to prevent our rescues from overheating. Running costs have to be very low as well. Realise I am asking the earth but can you advise please?

    1. If you can afford around €1000 to €1500, I would suggest getting a small (e.g. 4kW) split air conditioning unit professionally installed. This consists of an indoor unit that is mounted near the ceiling and a refrigeration unit that mounts on the outside wall. This type of air conditioner both cools and dehumidifies the air. The professional installation cost makes up most of the overall cost as the complete kit typically retails for around €600. Most split units can also operate in reverse to provide heat during the winter, similar to domestic heat pumps. So if the place uses storage heaters or oil heating, a split air conditioning unit will potentially offset its summer running cost with cheaper heating in the winter.

      The cheapest alternative I can think of would be a portable air conditioner rated around 3kW, which cost around €300 to €400. Unlike the split units, these only require someone handy with DIY to create a vent duct in the wall (same as for a vented tumble dryer) for the air conditioner vent hose. Like a split unit, these also dehumidify the air, but are noisier to run and most don’t operate in reverse, i.e. cannot provide heat in the winter. As they ventilate the hot moist air, they also have the advantage of freshing the air, especially with the place housing wildlife, since fresh air will seep in around the building to replace what has been vented.

      A 4kW split unit or a 3kW portable unit typically has a power consumption around 1kWh, which is 20c/hour based on the typical standard electricity tariff here. So 5 hours of total use per day would be around €1 / day.

  15. i am staying in dubai.. nw its good climate here with 35 degree celsius. sometimes i feel hot at home and i dont prefer to put AC at times as it makes the room cold so planning to buy a fan.
    i am confused whether to go for a pedestrian fan or a portable water cooler to cool the room so that v can use it full night also.
    its a 500sq feet 1 bedroom house

    1. A water-based air cooler evaporates water to lower the air temperature, so a window needs to remain open for this to work. The outdoor air also needs to have low humidity, so they are ineffective if is both humid and warm outside.

      If the windows are closed, the humidity will raise up until it is very humid and do little other than blow the humid air about. So after about an hour, the room will feel sticky and probably worse than had there just been a fan running.

      So if you are able to leave a window open at night and the outdoor relative humidity is low (below 50%), I would suggest going for the water based air cooler. Otherwise I would suggest getting a pedestal fan, run it on a low setting and aim it over the lower half of the bed at night.

      1. Thanx for ur reply.
        Can u plz suggest whether to go with pedestal fan or tower fan.
        Is tower fan effective for good cooling?

        1. My suggestion for a bedroom would be a tower fan as they take up less space than a pedestal fan. The noise and air flow are more pleasant than a pedestal fan with a steady shhhh sound and the airflow feeling like a steady breeze. I would avoid going for slim tower fans. Slimmer tower fans tend to be nosier as they need to spin their impeller faster to deliver the airflow.

          Pedestal fans better suited to larger rooms for greater air flow, such as a living room. They are also considerably cheaper than tower fans for the equivalent capacity. However, some people may find it difficult to sleep with the propeller-like sound from pedestal fans.

  16. Hi Sean, Thanks for your good explanations. I have a similar problem as some people above, I think. I live in a very humid house with mold and mildew issues in a quite humid city (Buenos Aires). I have been thinking of getting a dehumidifier for the bedroom, in order to help control some of the respiratory issues I’ve been having–which I think are due to the humidity. However I’ve noticed the bedroom is also quite hot (and we’re not even in the hottest time of year). I have been attributing this heat to the humidity. So I’m concerned if I use a humidifier it will make the room hotter (since it tends to raise the temperature 2C). Or perhaps the temperature will be brought into equilibrium. What would you suggest? There is also a window air conditioning unit which I thought I could run in tandem. I see and understand your warning against running a dehumidifier + cooler, but perhaps I could combine a dehumidifer with this window unit? Many thanks for your help.

  17. Hi Sean. I have a similar problem as some people above, I think. I live in a very humid house with mold and mildew issues in a quite humid city (Buenos Aires). I have been thinking of getting a dehumidifier for the bedroom, in order to help control some of the respiratory issues I’ve been having–which I think are due to the humidity. Also the room is quite hot, which I think is due in large part to the humidity (i.e. it’s much hotter than outside temp). I’m concerned if I use a humidifier it will make the room hotter (since it tends to raise the temperature 2C). Or perhaps the temperature will be brought into equilibrium, because by controlling the humidity the dehumidifier would both cool and warm the space–making it a wash in terms of temp. What would you suggest? There is also a window air conditioning unit which I thought I could run in tandem. I see and understand your warning against running a dehumidifier + cooler, but perhaps I could combine a dehumidifer with this window unit? Many thanks for your help.

    1. You can use a dehumidifier along with an air conditioner. Most air conditioners reduce the humidity as well as the temperature. On some air conditioners, it will have a separate setting or control knob position to operate in dehumidify mode. If your Windows AC unit does not mention a dehumidify mode setting, you can try setting its fan speed to low if it has that option. Most air conditioners concentrate on reducing the air temperature on high fan speed and reducing the humidity level on low fan speed.

      When a dehumidifier is run with an air conditioner in the same room/area, it will remove the heat given off by the dehumidifier, so in this instance you could run the two at the same time. The amount of heat a dehumidifier gives off is small in comparison to what even a small window air conditioner will extract.

      The air cooler I’m referring to in the article is a different type of unit, which is portable and does not have a vent hose. They work by evaporating water to try to cool it, adding humidity to the air. A proper air conditioner does not add humidity to the air (such as your window AC.)

      As a rough way to tell an air cooler and air conditioner apart – If the unit needs water to be added to work, then it is an air cooler which adds humidity to the air. If the unit has a vent hose, needs to be fitted in the window or has an outdoor unit, then it is a proper air conditioner and these generally help remove humidity from the air.

    2. The respiratory issues you are having haven’t much to do with the humidity, it’s the mold, mildew and the other exotic nasties of your region, reducing the humidity will cut down on their growth but it will also cause the spores to be released into the air more. You need full mold, mildew and bacterium/viral mitigation, possibly new insulation, windows, doors, new ventilation, etc.

      While the heat and humidity are a problem, the humidity is the least of your worries, get rid of those nasties, first.

  18. Hi Sean. A fantastic unbiased article I’ve found in the few days I’ve been researching. Thank you.
    Unfortunately my brain is totally overwhelmed from different advise and different units. I feel I should have it sussed by now but….. 🙁
    I wonder if you could help?
    I work in New Zealand from my rented home as a beauty therapist, in a room 10ft x 8ft . The room has a window but due to the nature of my treatments (facials and massage etc) and outside noise, am very often unable to open it. This hasn’t caused a problem until recently.
    A year ago I trained in a new treatment using a liquid product that needs a controlled environment of around 21c and 50% humidity to enable me to work with the product effectively and for it to cure correctly.
    My humidity is 66% and so need to correct it urgently before clients run away due to what they may class as bad workmanship 🙂 The temperature is currently ok. I have a plug in radiator for winter but might still need to control humidity then too.
    I’ve been advised to get a dehumidifier and air conditioner for summer (now here) and a humidifier for winter incase the humidity is then too low.
    Only having limited space around the furnishings and not wanting to clutter the room plus keep it looking professional I just don’t know which way to turn. How easy life would be if I could purchase just one unit that will do everything for me 🙂
    Do you have any suggestions?
    Thank you for taking the tme to read this 🙂

    1. I would suggest getting a compressor dehumidifier (refrigerant based) that has a digital humidistat. Going by the room size, a small 10 litre-rated dehumidifier (typically ~€120 here) should be sufficient as long as the door to the room remains closed. If the door needs to be open, I would suggest a 20-litre model (typically ~€160), as most of the dry air will go out the door until the outer room/hallway humidity level also drops.

      One thing to watch out for is the temperature when the dehumidifier is operating as it will warm the room by 1 to 2C. If the temperature increase becomes too much of an issue, what you can try is running the dehumidifier overnight set to 50%, so that it only needs to operate intermittently during the day to maintain that level.

      If you can afford to get an air conditioner professionally installed (typically €2000 for a small system here from what I heard), that would provide the best control over both the temperature and humidity levels. Air conditioners can reduce both the temperature and humidity levels and will generally bring the humidity level to around 50% to 55%. Most air conditioners can operate in reverse where they provide heat in the winter, using roughly 1/3 the electricity of a plug-in electric heater. They generally do not dehumidify in heat mode, so if the humidity level drops too low, you can raise the humidity level with a small humidifier without the air conditioner taking it back out when operating in heating mode.

      1. Thanks so much for your response Sean.
        I’m now trialing a dehumidifier with added hydrometer. It seems to be working well at the moment so thank you for your advice. If the temperature does rise, I’ll certainly bear in mind the option of running the dehumidifier overnight too.
        From what you’ve said about Air Con units, that’s something I’ll definitely be looking into for next summer 🙂
        I understand things a lot more clearly now so thank you very much for your help and explaining things in laymens terms for me 🙂

  19. Hi Sean.

    I’ve been reading your post and comments, very informative, thanks. I wanted advice on my particular case. I live in Madrid and right now it’s still cold in my house, but I have a massive humidity problem. There is mold growing everywhere, on the ceiling, on my wicker chairs, on my wooden chopping boards in the kitchen. I know I need to act fast. But, I was wondering will installing an air conditioning unit with a dehumidifier function solve my issue or will I need an actual stand alone dehumidifier??

    1. I suggest getting a stand alone dehumidifier to start with. An air conditioner will transfer some heat outdoors when operating in dehumidify mode, whereas a dehumidifier transfers its waste heat back into the room due to the complete evaporator and condenser cycle being located within the dehumidifier. As a result, it will cost more to run an air conditioner than a dedicated dehumidifier during colder weather as your heating system will need to replace the heat that the air conditioner expels while dehumidifying the air.

      The exception would be during the warm weather in which case you can operate the air conditioner in dehumidify mode, where the cooler air is a benefit. Both air cooling and dehumidify modes cool the air and reduce the humidity simultaneously, however, the main difference is how the air conditioner adjusts its compressor and fan to control the ratio of dehumidifying and air cooling. For example, in dehumidify mode it will aim to reduce the humidity level by reducing how much it cools the air. Only a stand alone dehumidifier can reduce the humidity without cooling the room as it has no outdoor component.

  20. I need some suggestion because my situation is a bit hard I live in a place where the temperature is 108F and the RH between 40-60%
    the main in my room is close room without windows and i can’t make a hole in the wall so the portable AC is useless method.
    can you suggest any thing to my case

      1. Unfortunately with that high temperature, the only suggestion I have is a split air conditioner. There is a portable type that has a portable outdoor unit, which connects to the indoor unit with a cord, similar thickness to a garden hose. As the outdoor unit is portable, you can take it in at night to close the door. This would let you have the door just wide enough for the lead to pass through, unlike the gap required for a portable AC vent hose. On the other hand, these portable split AC’s are considerably more expensive than a typical portable AC, but do have the advantage of not requiring professional installation or drilling any holes.

        If it’s just a temporary measure (e.g. unusually hot weather), try drinking plenty of ice cold water, e.g. keep bottles of water in the fridge and put plenty of ice cubes in each glass. You could also try freezing some ice gel packs to try using them in reverse to a hot water bottle, although just beware that these will get wet from condensation.

  21. I actually have a related question!

    When I’m outside and a breeze is just right, I find this incredibly relaxing.

    Is there a way to bring this feeling indoors?


  22. Hi Sean,

    I have a similar issue to your original article. I live in the North West of England and in the Summer it often gets very warm and humid making sleeping a real problem. I live in a small ground-floor flat and my lounge and bedroom often get high humidity levels of around 60-70% but with temperatures of 20-24 degrees Celcius.

    I can’t really open my windows due to a neighbourhood cat often trying to climb through them when I do and the noise from the neighbours. So I have bought a dehumidifier to help reduce the humidity levels down to around 55% and wondered if I could use this in combination with a ceiling fan to help me feel cooler and more comfortable?

    1. You can use a dehumidifier in combination with any type of ordinary fan, e.g. desk fan, pedestal fan, ceiling fan, column fan, etc.

      I don’t recommend running the dehumidifier with the window open. E.g. if you want to open the window for a while, switch off the dehumidifier until you close the window.

      1. Thanks very much for your help Sean. I’m really impressed with my Meaco 12L dehumidifier. I’ve set it to 50% humidity and leave it running all day and night as it comes on intermittently to adjust the humidity as necessary.

        I tried it in combination with my ceiling fans and while with the fan on I do feel a little cooler after an hour or two, it seems to increase the overall humidity significantly and make the room feel much hotter (even with the dehumidifier running).

        I’ve found the best solution is to not use the fans for more than an hour or at all as at least with them off and the dehumidifier running, my overall levels stay around 55% or slightly above.

        Thanks again for your help.

  23. Good thing I found your post first before heading to the appliances shop and purchase a disaster piece of cooler. Thank you!

  24. Hi Sean
    Great article. We have a new condo we are renting for the summer. The weather in NS Canada is similar to Ireland I should think so I found your write up very helpful. When we bought the condo it came with a portable air conditioner but we feel there are parts missing and the windows are casement or crank Windows so the attachments don’t seem to work. The hoses also seem too small to reach the window. Do you just buy more hose to hang out the window and leave them open? Seems counter productive. We have a dehumidifier also so we are going to try that first. Any experience with portable air con in crank Windows? The temps though seem to hover around 24 25 with the windows closed. We must close them at night for the train……during the day is fine.
    Connie Monk

    1. Here in Ireland, most homes have casement windows, so indeed this is an issue when it comes to a portable AC hose. If it is calm outside or a light enough breeze such that you don’t feel air blowing in/out with the window open, the AC’s vent hose will generally work fine. However, if there is a strong breeze or a draft caused by a fireplace, the warm air blowing in will reduce the AC’s effectiveness, wasting energy.

      There is a kit you can get that goes around the open casement window, allowing the AC to vent its heat with minimal air getting back in. Going by this Amazon page, it comes with a 1.5m (5ft) 5″ or 6″ hose depending which you choose. The included hose can be attached to your AC’s vent outlet.

      The AC will be several times more effective than the dehumidifier. Most portable ACs typically extract three times the amount of water compared to a typical 20 litre (or 50 US pint) dehumidifier with the same room conditions. The AC also has the advantage of cooling the air due to venting the warm moist air outside even when operated in dehumidify mode.

      To reduce running costs, you could run the two in alteration, e.g. run the portable AC for an hour or two to quickly bring down the temperature and humidity level, then switch off the AC and switch on the dehumidifier to maintain the low humidity level.

  25. Hi I am in a situation of very very low humidity as living in the midst of a desert and to increase humidity in the house for babies and me to be comfortable, what should I do? Will a water cooler be a better option? Or a humidifier? I read that humidifiers if not cleaned all the time will further cause health problems so is water cooler a better option?

  26. To add to the above situation we are running ac all the time as it’s also very very hot here which further increases the dryness and itchy eyes n throat.

  27. Thank you for all the info in one place! I’ve been looking for hours trying to find what I need, started with no information at all and now I feel I can give a lecture on it! I feel very unfortunate though because there seems to be no solution to my dorm room temperature/humidity. Here in Syracuse the first months are terrible humid (today 91%) (90*F) and our rooms have just one tiny old fashion window that pull out like an oven and take (valuable) space/cause a few injuries from running into the corners. We have the fans but there is always a discomfort. The OTHER issue is that I am from the other side of the country, and a storage company picks up/stores/drops off everything over summer break. This gets very costly and the more I obtain the more expensive. Other factors: very very small space, and limited in dorm storage during winter when the device is no longer needed. Any recommendations on what can help would be appreciated. Thanks! ( I know that was a lot)

    1. Oops, one last thing. Would you recommend an “Outdoor” air cooler. I read that those are better for high humidity.

  28. Informative but still not sure what is best. i wanted to get a portable air cooler with dehumidifier (but realised they come with humidifiers and have not seen one with a dehumidifier). Fortunately i now know not to try running a dehumidifier and air cooler together. However would an air cooler possibly be effective even if not as much so as usual if i run it in a humid environment with the window open and use some not electric dehumidifying product (like damp absorber) as they are much lighter, easier to clean, less expensive to run at least and no unsightly tubes connected to the window (which in my study would mean going over a bed ) and the place is small the windows rattle if open which is not good at night. The store (several) promoted the air coolers disregarding concerns about humidity so not sure what to do. thanks for the information.

    1. Unfortunately, the non electric damp absorbers collect water at an extremely slow rate, usually under 50ml per day. For comparison, a typical evaporative air cooler puts out 1 to 2 litres per hour into the air, depending on the size.

      Evaporative air coolers ideally requires two open windows, a steady breeze coming in the window next to where the air cooler is located and another window or door open to let the humid air back out. As the air comes in, the air cooler will evaporate water to cool the air. This in turn will cool the room slightly by the time this humid air goes out another window. This of course requires the outdoor humidity level to be no higher than around 60%. Once the windows are closed, the air cooler will no longer work properly as it will quickly raise the room’s humidity.

      1. Well said… and so ideal if you live in India with a shady verandah or with a private garden fountain in hot Morocco ;-))))
        Personnally, as I do not want to spend too much electricity either, a simple ventilator with a damp towel or some cool spritz will be much more effective to cool my spot (incl. my bed).

  29. Hi, My apt. In Northeast PA, SUMMERS can be very humid or plain dry & hot. I only have 3 tiny windows of which 2 in one room do not open. Landlord needs to charge extra rent to use the small window type AC, but no charge for portable. I also plan on getting a fan for circulation. What kind of portable AC needs purchased, a vented one with hose not allowed either. Thank you!

  30. Hi Sean
    Great article, i live in south west england and the summer can get pretty warm and humid for me at least. i live in a first floor flat, which has a lounge/kitchen as one room with windows either end the kitchen has a cieling extractor fan made be ferr*b which goes to the outside wall through the roof space.
    i was wondering if i run a evaporating air cooler at the lounge end of the room with the windows open and put the extractor on for periods (as it is noisy) this would conter the humidity going even higher. i know a portable a/c vented through the lounge window would be best but they around £300 for 9000btu and evaporating air coolers seem lot cheaper,
    Any advice would be great

    1. Unfortunately most extractor fans don’t provide a lot of airflow due to their grease filter, however, you can give it a try. The air cooler performance will vary depending on the humidity level, which is why they don’t have a BTU rating. As a rough guide, one litre of evaporation per hour provides 2180 BTU of cooling. If your windows open wide enough, you can try aiming a pedestal at one to force air out, which in turn will draw air in the other windows. This will be a lot quieter than running the extractor fan.

      At the end of the summer, have a look around the various DIY stores such as Homebase, B&Q, etc. for clearance sales on air conditioners. My brother bought a 9000BTU vented air conditioner for £110 at Homebase (in Northern Ireland) a few years ago during their end of summer sale. A proper air conditioner is like night vs day over an air cooler as it gets rid of the ‘stickiness’ feeling, especially on warm humid days where an air cooler is barely more effective than a fan.

  31. Thanks for such a quick reply I’m impressed. Yes I see what mean. I have a tower oscillation fan which does a decent job. But I think I’ll do like you suggest and either but the bullet on a new portable air con unit and hose or see if one pops up on gumtree or eBay close enough to collect. Or as you say look for a end of season deal at b&q .homebase etc
    Thanks again for such a informative article and reply

  32. Hi Sean

    Any suggestions what to do for a screened in porch (approx 250 sq ft with 15 windows) when it is very hot and humid here in the northeast.
    We can’t even sit in the room on hot/humid days, even at night.

    1. With the large number of windows, the porch is effectively a greenhouse. My first suggestion would be to get solar control film that sticks to the glass. Some films can block out around 80% of the heat getting in, which will reduce the heat build-up during the day. There are YouTube tutorials that show how to install it. Just make sure it’s a removable film as this way you can remove it during the winter months where the extra heat from the sun is beneficial. Most of the films give a mirror effect on the outside.

      If you still need to resort to an air conditioner, the window film will greatly reduce its running cost, especially with that number of windows. I suggest putting it on low or medium fan speed as the lower fan speed puts more effort into moisture removal. Try to get the humidity level to or below 55%. Then use fans around the place to help dissipate the drier air and help make the air feel a little cooler.

      1. Hi Sean thank you for your quick response. I should have clarified that the windows are mostly screens – there are plexiglass attachments that we remove for the season so it is a screened in porch – so most of the 15 windows have been removed and there are mostly screens – with no breeze for the majority of the summer.
        So we figured air conditioning would be a waste when the windows are off.
        Also, the windows are not floor to ceiling – they end half way.
        So does that change your suggestion?
        Thanks again

  33. Hi Sean
    thank you for your quick response
    I should have clarified that the windows are screens, not glass. They all have plexiglass attached that we remove in the spring and keep off until late fall to make it a screened in porch. The windows are also halfway from floor to ceiling.
    So when its all screens we figure air conditioning is a mute point. But in summer there are many days/nights without a breeze coming through the screens and a humidity level of 90% or more. Ceiling is too low for ceiling fan too
    So wondering if you have different suggestions now that I gave you more specifics.
    I tried to paste a picture of the room in this message but was unsuccessful. Can I email you or upload it?
    thank you!!

    1. In this case, the only thing I can think of would a few tower fans distributed about the place. These cost around around $60 for a moderate size fan in the US, but give a breeze down to the ground, unlike a pedestal fan where it mainly blows at one part particular height. I suggest getting one to start to see what it’s like for noise and effectiveness. Personally I wouldn’t go for a Dyson fan unless you have a big budget and want something very stylish.

      If it’s dead calm inside, an air conditioner will provide some cooling up to the height of the base of the windows. While warm air rises, cool air settles towards the ground. This means as long as there’s no significant breeze, it will likely cool up just above the base of the windows. However, unless the base of the windows is above seating height, I wouldn’t recommend one as most of the cool air will flow out the windows.

  34. Hi Sean,

    This is a good read really interesting and informative. What will be your best bet for a 4.7 square meters room with 2 30×30″ closable window directly heated by Sun from 10am to 4pm. Room temps from 32-37 degrees celsius during summer with a relative Humidity of 75-95%. Thanks

  35. It is 75degrees in home with all electric air conditioner in Southern La. Temp outside77 with 60-70 percent humidity outside and just bought a crane EE1000 dehumidifyer. Hopefully my answer. Seems cooler in a 300 square ft room. Window is closed and never used.

    1. The dehumidifier when working creates heat. Another thing to be aware of, check all of your windows and doors in your house when the humidifier, air conditioning isn’t running nor is the fans on them. Then take lit incense, put it by each window, run it along the sash, the sill and along the corners, see if the smoke is being “blown” in towards the house or being sucked through the paneling. This is an indication of a thermal leak. You should caulk the outside windows and doors with the appropriate stuff for your area. So much of the humidity and heat pushing into the house comes from leaks like these. Also, in winter you can feel cold pushing in.

      Most windows and doors, the R and U factors are horrible, and you lose valuable comfort in the process.

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