Calculate the power of the heater you will need
Calculate the power that you need to run a heater
To calculate the power needed we need to know three things.
First of all to measure the space you are heating, do a rough calculation by multiplying the length, width and height of the space together. For instance if I were heating a one car garage of dimensions 6m X 5m X 2m i would have 6x5x2 = 60m³
Next consider the temperature that you wish to raise the space by. When assessing this figure, think of the coldest average temperature that you experience in the part of the world you live in. It's probably best not to calculate for those odd days that you may get where it is unseasonably cold as you can always supplement your main heater with another standby one if the temperature really does plummet. Think of an average winters day and then think of the temperature that you would be comfortable working in. A comfortable temperature inside the home may be around 21°-23° Celsius but in your shop or garage you may be able to get away with lower than this, especially if you are working. For the sake of this example lets say you would be comfortable in 18°C
The average temperature where I live in the UK on a winters day is probably no less than around 0°C so I would need to raise the temperature by 18° using the heater.
The insulation is the next factor to consider. There is another article that goes into more detail about insulation and you should read that to get some advice on insulating your workshop. However for the sake of this calculation we should try and decide on which of the following levels your building sits at. The figure given is then used in the calculation.
| No insulation | x 3.5 |
| Some Insulation | x 2.5 |
| Well Insulated | x 1.5 |
| 100% Insulated | x 0.5 |
Let's assume our Garage is well insulated and finish our calculation. To find what power output you would require to heat a 60m³ garage with good insulation to a temperature of 18 degrees when the outside temperature is 0 degrees we multiply everything together and then multiply the final result by four to get BTU (which is what all heaters are measured in)
60m³ X 1.5 X 18°c = 1,620 multiplied by 4 = 6,480
So we would need a 6,500 BTU heater for our situation. To get a figure in KW's all you need to do is divide this figure by 3400 so in this case we would need a 1.9KW heater. As you can see, everything is directly proportional to the outcome - If you double the space to heat, you need a heater twice as big. Another point to note is how important the insulation factor is and how much energy and money it can save you in the long term.