How do DEhumidifiers help save on energy bills?

masonic

Petriix said:

It's utter nonsense to suggest that heating up a whole house of cold air uses a 'negligible' amount of energy. In the current times where some people are genuinely struggling to pay their spiralling energy bills, understanding the difference in costs is really important.

The most significant factor is that the energy used by the dehumidifier is all retained in the house as heat while the ventilation method simply pours the energy out into the atmosphere.

Standard rate electricity is approximately 3 x the cost of gas heating (factoring in losses) so that's an important consideration. Running a dehumidifier overnight on Economy 7 (or another time of use tariff) is almost certainly cheaper than the equivalent gas heating. 

If you do ventilate then do it in the warmest part of the day to minimise lost heat. Don't leave your bathroom window open for hours because, once it's cold, the air becomes far less effective at evaporating the moisture from the surfaces. It's far better to extract the warm, moist air. 

The cost of reheating a 40 m3 roomful of air for me is between 0.1 and 0.2 kWh (what I've measured in practice also lines up very well with the calculated energy requirement), which is 1% of my daily energy consumption at this time of year and costs me about 3p on my current tariff (and would come in at about 10p on a single rate price guarantee tariff). If that isn't negligible, I don't know what is. I'm happy to bear that small cost to deal with an extremely humid room within minutes, where a dehumidifier would take a lot longer. I reserve the dehumidifier for 'maintenance' of humidity rather than to deal with an acute problem.

Grandad2b

Petriix said:

It's utter nonsense to suggest that heating up a whole house of cold air uses a 'negligible' amount of energy. In the current times where some people are genuinely struggling to pay their spiralling energy bills, understanding the difference in costs is really important.

The most significant factor is that the energy used by the dehumidifier is all retained in the house as heat while the ventilation method simply pours the energy out into the atmosphere.

Standard rate electricity is approximately 3 x the cost of gas heating (factoring in losses) so that's an important consideration. Running a dehumidifier overnight on Economy 7 (or another time of use tariff) is almost certainly cheaper than the equivalent gas heating. 

If you do ventilate then do it in the warmest part of the day to minimise lost heat. Don't leave your bathroom window open for hours because, once it's cold, the air becomes far less effective at evaporating the moisture from the surfaces. It's far better to extract the warm, moist air. 

The energy required to heat a fairly small houseful (60m^2) of dry air from 0C to 18C is about 1kWh. Most houses are designed for 2 air changes per hour which means in winter you're likely looking at 25kWh just to deal with the design ventilation. Most of us lose that energy to the outside air whether we open windows or not.