To calculate the consumption of an electrical appliance in kWh, you have to take into account three factors:
The calculation is as follows:
[number of hours’ use] x [number of days’ use] x ([capacity of appliance expressed in watt] / 1,000) = number of kWh
The capacity should be divided by 1,000 to convert the number of watts into the number of kilowatts. This finally gives us the number of kWh (kilowatt hours).
Imagine the use of an electric fan heater (power of 2,000 watts) 1x per day for 30 minutes (the time it takes to have a shower).
Assuming that the heater is used for 150 days, i.e. the five coldest months of the year (October, November, December, January and February), we obtain the following result:
|hours / day||0,5 hours (or 30 minutes)|
|days / year||150|
|Capacity of radio alarm||2,000 watts|
Annual electrical consumption of an additional heater: 0.5 x 150 x (2,000 watts/1,000) = 150 kWh
In the table below we assume that the vacuum cleaner is used for two hours once a week.
|hours / day||2 hours|
|days / year||52 days|
|Capacity of vacuum cleaner||800 watts|
Annual energy consumption of vacuum cleaner: 2 x 52 x (800 watts / 1,000) = 83,2 kWh
Take a look at the list giving the consumption of the most common electrical household appliances.
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