How Much Do They Cost to Run?
A 300w panel will draw 300w of electricity per hour at maximum power and 98% of that power is translated into energy that provides heat. However, once the room has attained the desired temperature, an in built thermostat will ensure that the panel will not overheat and that it will draw electricity down to as low as 30% of the time. The amount of time that it will be running at this efficient level will depend on exactly where the panel is situated and what it is trying to heat.
If you use an external thermostat to control the room temperature even greater efficiencies can be obtained. We have found that the optimum temperature in rooms can be as low as 18 degrees C, and to be sitting in the room very comfortably, compared to 20-21 degrees C required by conventional convector heaters.
So, if a kilowatt hour of electricity costs about 18 pence per unit (this will depend on your tariff) then our 300w heater will cost about 5.4 pence per hour to run to get the room up to temperature, and as low as 2 pence an hour to maintain the temperature.