Cost of running a dehumidifier (sp)

yummymummy1987_2

Ive been having problems with damp so my landlord is bringing round a dehumidifier. I am just wondering how much i should expect this to cost to run. On some sites its saying its literally pence per hr. Im not sure which brand or size it will be yet
Just want a rough idea

Thanks in advance

maninthestreet

The dehumidifier should have a label stuck on it somewhere (probably on the back), which states the power consumption in watts. Typicallya dehumidifier uses about 200-300 watts, so would cost about 2p - 3p an hour to run.

John_Maclaren_NZ

I have been trying to find the true cost of running a dehumidifier, it seems that in addition to considering the cost of running the equipment you need to consider

1. The extent of the damp problem governs how much it actually runs

2. How much heat is put out by the dehumidifier (therefore how much saving in heat from other sources results)

3. How much less heat is needed from other sources to get the house comfortably warm (less heat is needed to feel comfortable when the air is dry).

Is any reader studying this at Uni. who can tell me?

cybergibbons

A lot of dehumidifiers have a humidistat, which is to humidity as a thermostat is to temperature. This will cause the dehumidifier to click on and off periodically.

Most dehumidifiers running 24hrs a day won't be able to reduce humidity below 35% RH, yet will only need to run maybe 30% of the time to get the house to 50% RH (which is on the low end of the recommended range).

A dehumidifier, if considered as heater, is actually more than 100% efficient. I know that sounds odd, but every watt you put into it goes out as heat, but in addition the latent heat of condensation is released when the water condenses on the coil. This means that a 300W dehumidifier can in fact pump out 700W of heat. You get more additional heat the higher the relative humidity.

This means that if your heating is electric anyway, using a dehumidifier is a winner.

If you have an air conditioner it is largely redundant running a dehumidifier - the two will both extract moisture but also fight each other with the heat.

Regarding the perceived temperature - there are a few effects here. Firstly the heat index. A room temperature of 21C will have a heat index (i.e. the human body will perceive it as this temperature) of 20C at 85% RH (you certainly have a humidity issue if your RH is this high). At 50% RH it will feel more like 25C. Some people are actually very sensitive to humidity in this sense, so your mileage may vary.

If you are drying clothes, towels, waiting for your hair to dry, then the lower humidity means that less heat is required to evaporate the water, which will have have a noticeable effect.

Don't expect to be able to extract the nameplate litres/day rating - my dehumidifier is rated 12l/day, but in a typical slightly damp house 5l/day is the maximum that it could even theoretically remove from the air.

It's normally best to run the dehumidifier for the first month or so all of the time - this will pull down the humidity as low as it will go. Then set it to run on the humidistat to maintain the humidity. Rather than measure the RH all of the time, it's best to judge the success of the dehumidifier by the reduction of the symptoms - condensation on windows and walls, damp patches and mould.

If there is a real damp problem, you need to try and fix the source of the damp or you are fighting a losing battle really.