Will a dehumidifier heat a room

This is a very common question, when working out the actual cost of running a dehumidifier a lot of people start to look at other benefits from the running cost, such as the heat produced by the dehumidifier, and what, if any, effect it will have on the room temperature.

First of all, there are two types of dehumidifier technology, one is referred to as a rotary design and uses a compressor similar to a fridge, the other is a type which uses desiccant gel particles (similar to the little packets you get in packaging), the desiccant removes the moisture from the air, and water is then extracted by heating the desiccant over a small heating element. It is this internal heating element which results in the dried air leaving the dehumidifier being warmer than the moist air entering it, resulting in a heating effect and in a small room this will be noticeable by an increase of upto several degrees.

A damp room will always feel colder due to the high humidity level, and its effect on skin temperature, and so removing the moisture with either of the dehumidifier types will, effectively, make the room ‘feel’ warmer and more pleasant without actually raising the room temperature itself. However if you are looking for a dehumidifier which not only removes moisture and prevents damp but will also justify a percentage of its own running costs, through raising the actual room temperature, then only one of the two available dehumidifier types will be suitable, and this will be the desiccant design due to its small built in heating element.

If room heating is a requirement of your choice of dehumidifier then you shouldn’t consider the rotary compressor type, as these do not heat the air, they work simply by removing moisture by passing the air over cooled coils, so that it condenses back to water and although they will still prevent damp issues by lowering the humidity level, they will not heat the air as part of the process nor return any warmed air into the room, and so although this design is still effective at reducing damp, the heating effect will be virtually non existent.

The best & only choice for removing damp and also increasing the room temperature, would be the Desiccant Dehumidifier. Because these have a small built in heating element to regenerate the desiccant gel, the heat produced through normal operation is not lost or entirely absorbed into the gel, and so all of the heat is blown into the room by the powerful fan, so not only does it remove moisture from the air, it heats it as well before sending it back into the room. I have personally tested several of the dehumidifiers on the market, and the temperature of the air being blown from the dehumidifier ranges from 7c to 12c higher than the ambient temperature of the room air that is being sucked in, which over several hours of normal use, is effective at raising the room temperature by a similar margin.

If you dry washing indoors then you certainly need to invest in a desiccant dehumidifier, as the evaporating moisture will soak into the building fabric, eventually leading to expensive damp problems and even potentially dangerous black mould problems. In fact a large percentage of damp issues and landlord – tenant disputes are actually caused by frequently drying washing on radiators, over airers or in front of fires, and this includes the variety of heated clothes driers often touted by Money Saving Experts!.

It is worth pointing out however, that during very cold periods, a dehumidifier alone, may not be enough to make the room warm enough to sit in for long periods of time, and therefore a dehumidifier shouldn’t be considered to be a primary or sole source of heating for a given room during the colder winter months but rather a background source of heating – however it does mean that the cost of running it has a two fold benefit, or three if you also count drying washing.

However what the dehumidifier will do, in addition to removing damp problems and lowering humidity is to create a very good and effective source of background heating, warming the room by up to several degrees and therefore reducing the amount of heat required from other forms of heating, therefore reducing overall heating costs. So if you have a damp or condensation issue and are faced with having to buy and run a dehumidifier to address it, you may as well get as much benefit as you can.

Because they use a small heating element, desiccant dehumidifiers do consume slightly more Electricity than their rotary counterparts, making them slightly more expensive per hour to run (The average running cost of a Desiccant Dehumidifier in the UK in 2023 is around 9p per hour). Don’t forget that once the humidity level is addressed and the humidistat begins to cycle the unit, the power consumption won’t be continuous, but should eventually reduce to only 2 – 3 hours runnng per day.

Since desiccant models also return heat to the room, raising the room temperature and so reducing the reliance from other forms of heating, the overall daily running costs are mostly recouped and shouldn’t be a cause for concern. Certainly the cost of running a dehumidifier is far less than the eventual cost and inconvenience of fixing longer term household damp issues!.

The other advantage of desiccant dehumidifiers, is that they are quiet running and so ideal for a bedroom or other living area, as they produce no more noise than a small desk fan, compared to a rotary type which can be very noisy in operation.

Desiccant dehumidifiers can also serve as a much cheaper means of drying washing, and popular models such as the Meaco DD8L even have a built in program designed for doing that. Simply hang your clothes close to the dehumidifier, select the dry washing program and dry clothes much faster than airing alone whilst preventing damp problems and save around £1 on a tumble drying cycle!.

When comparing running costs, also note that many modern dehumidifiers now have a ‘humidistat’ control mentioned elsewhere in the article. This works much like a thermostat on a conventional heater, and senses the humidity level in the room, and so switches on the dehumidifier only when moisture levels reach problem levels – saving additional energy.

My own experience with a desiccant dehumidifier are that they will initially run at full power for between several hours and a full day and remove around 5+ litres of water whilst the humidity level is initially reduced down to the level selected on the ‘humidistat’, after which the dehumidifier will only operate when the humidity levels increase above the comfort level selected on the control panel.

I set my own dehumidifier to keep the room at no higher than 50% rh and although my dehumidifier was left on for 24 hours a day, after the initial running period to reach the desired 50%, it was only actually physically running for around 2 hours per 24 hour period, making it very cheap to run. If running costs are an issue then the setting can be decreased to 60%rh, which is the limit recommended for preventing condensation resulting in damp and mould.

I have tried several desiccant dehumidifiers on the market over the years, and the one which I highly recommend personally, and of which I found to be the most effective at not only removing moisture but also heating the room and drying laundry is the Meaco DD8L