CALCULATING RADIATOR POWER RATING
29 June 2009
In this country we use the British Thermal Unit as a measure of power rating. It is shortened to BTU. To calculate the radiator BTU you need to measure the room size and multiply the room length by width by height (all in feet) and then multiply by four. So, for example, if the room measures 12 ft long by 9 ft wide by 7 ft high you will need a radiator with a power rating of 3,024 BTU (12 x 9 x 7 x 4). If you don’t do this calculation you may end up either with a permanently cold room, or on the other hand you could spend too much money on a radiator that is larger than necessary. This calculation gives a good average figure. The purists will point out that, strictly speaking, you need to take into account factors like heat loss due to the amount of window glass; whether the room faces north or south; the type and amount of insulation, etc.
Whilst this method gives a good average figure, if you have a modern home built to modern build specifications you can reduce the power rating by 10 to 20% due to the higher level of insulation.
Be careful if using on-line BTU calculators. Some web sites appear to be a bit like 'over-the-top' salesmen. The calculations indicate you need radiators far bigger than necessary and if you use these figures you may end up paying more than you need to heat your home.
If you are not sure, our trained staff will be happy to make those calculations for you.
