by James Michael Brown

(Blackpool UK)

I have just purchased a DeLonghi DES14 Dehumidifier and I have found that with the humidistat set just above medium I can attain a relative humidity of 55%. Is it possible to estimate the running costs of this machine at that setting.

Answer

Hi James, thank your for your question.

To estimate the energy cost of running your dehumidifier you need to determine the amount of electricity used and the price of that electricity per unit.

The unit used to calculate energy consumption is the "kilowatt hour". An appliance consuming 1 kilowatt (1000 watts) per hour will consume one kilowatt hour per hour. A 100 watt light bulb running for 24 hours will consume 2.4 kilowatt hours of electricity over that 24 hour period.

Electricity suppliers charge different prices per kilowatt hour. They also have a variety of tariffs which may cause the price per kilowatt hour to be higher or lower at different times of the day and/or on different days of the week (weekends charged at a different rate from week days, usually).

The energy consumption of the DeLonghi DES14 is 230 watts per hour. Your chosen setting for the humidistat and the conditions prevailing in the space in which the dehumidifier is located (area of the space, temperature and relative humidity) will determine the number of hours per day that the dehumidifier will operate to maintain your preferred level of 55% RH.

In order to make your calculation you should first examine the tariff applied by your electricity supplier. Determine the number of hours in each week at which the varying rates (if you are subject to variable rates) apply and note the numbers of hours at each rate. When added together these figures should total 168.

Estimate from your observation of the dehumidifier the number of hours each week that the dehumidifier is operating (that is to say when the compressor is running) and convert this figure into a percentage of the total hours in one week. Apply that percentage to the varying rates so as to calculate the total number of

kilowatt hours used and to estimate the cost.

To simplify this here is an example using fictional figures for illustration.

Rate 1 applies 80 hours per week at 15p per kilowatt hour

Rate 2 applies 60 hours per week at 10p per kilowatt hour

Rate 3 applies 28 hours per week at 05p per kilowatt hour

The dehumidifier operates for 70 hours per week.

70 hours = (70/168) x 100 = 42% (rounded to the nearest whole number) of the week.

Cost per week at Rate 1 = (80 x 42)/100 x 15p = £5.04

Cost per week at Rate 2 = (60 x 42)/100 x 10p = £2.52

Cost per week at Rate 3 = (28 x 42)/100 x 05p = £0.58

Total weekly cost = £5.04 + £2.52 + £0.58 = £8.14

To this cost you should add a small amount, say +10% to cover the modest cost of the fan operating (to sample the air) while the compressor is not working.

Of course there are many variables that cannot be taken account of in this simple calculation but it will provide you with a reasonable estimate of the weekly cost of operating your dehumidifier.

Tom (Webmaster)