Radiators are currently the most common option to disperse the heat produced from a boiler around your home or office space. But what many people don’t understand is that installing radiators that are too small in your heating system will cost you more to run.

Simply put, undersized radiators cause your boiler to have to work harder, for longer, to reach and maintain the required temperature, and the harder the boiler has to work, the more it costs. This can be a very expensive way for you to run your heating, especially if your home or office is still not warm enough for you.

What size radiator should I choose?

So, it’s always best to oversize the radiators, which will allow you to run your boiler flow at a lower temperature which is more efficient and saves money.

Flow temperature is the temperature of the water from the boiler that heats up the radiators. The lower the temperature the less work the boiler has to do and the less gas (or LPG, or oil) is used. But you can only run the flow temperature lower if the radiator is oversized.

How are radiators sized?

Radiators come in many different sizes and depths. The output of the radiator is based on “overall size”. The depth of the radiator is also very important as you can increase the output by increasing the depth (rather than length) from a single convector to a double or even triple convector – which is really useful if the available wall space is tight.

It’s worth noting that not all radiators are created equal! They don’t all have the same outputs even if they are the same size, different quality and designs can vary the output. Unfortunately some of the nicer looking, designer radiators have a far lower output so it’s worth checking this before you make a final decision.

How do you calculate what size of radiators you’ll need?

Every radiator is also sized based on its output, this will be in British Thermal Units (BTUs) or in Watts. When buying a radiator, most manufacturers will provide a basic radiator sizing calculator. By entering information such as room sizes, wall and floor construction the calculator will give you a pretty good idea of what size radiators are needed.