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Which size radiator do I choose?

February 28, 2019 Paul

Choosing the right size radiator can hugely affect the comfort of your home.

Too many times homeowners have overpaid on energy bills or been dissatisfied with their heating solutions. Considering basic information about your situation and its requirements can save a lot of hassle.

Our guide will help you pick out the perfectly sized radiator. The most cost effective and energy efficient option is just a simple calculation away.


The size of your room drastically affects the size of your required radiator. A small radiator will struggle to heat a large room effectively because of the amount of air they are able to act against. This may result in an unbalanced room temperature and long-term energy wastage. Large radiators will be able to quickly alter the temperature of a small room, however can be more expensive to run.

Getting the exact size is important. To work out your room’s floor area you need to measure and multiply the floor length by its width. For example, a room which is 4 meters long and 3.5 meters wide has an area of 14 square meters. To heat this room effectively you would need the correct size radiator model with a minimum wattage of 1430 watts.

Heater Shop’s room calculator provides the most suitable radiator wattage for your room size; it forecasts the model’s ability to obtain and maintain an ambient temperature of 21°C. There are other factors to also consider when determining the size of radiator to suitably warm your room.


Taking into consideration your building’s thermal insulation is very important for selecting the correct size radiator. Rooms with poorer heat retention may require a larger radiator to effectively regulate the ambient temperature. Remember, the insulation quality could vary throughout the building; affecting factors include the number of windows in the room or if it’s an attic room.

If it’s a new build it will usually have very good insulation, but older builds could be leaking a lot of heat. Brick, concrete and wood builds each have different insulation properties, so think carefully about your options or consult a professional. If you are unsure Heater Shop has a technical team available on 01473 276686.

Where you are in the country

From the hilly Hebrides to the white cliffs of Dover, where you are in the country largely affects the recommended size of radiator you require. The UK is 601 miles long and experiences frustratingly odd weather patterns; the average outside temperature affects the correct radiator size. Whether your location is rural or urban also affects the suggested heating solution, as urban cities slightly produce and retain more heat than rural communities.

Our room size calculator gives an estimated recommendation depending on your location, certain sections of the country needing a more powerful radiator than others.

The way your room is facing

Depending on which room you are aiming to heat, it may receive more sunlight than others. The orientation of your room can affect the required output of your radiator and therefore its necessary size. This is a commonly overlooked factor which could save the operator a lot of money over the calendar year.

Skylights, bay windows and French windows all factor into the successfulness of keeping your room well heated. The quality of the glass and the construction of the window should be considered as well as the height and structure of the room. The radiator’s placement in the room will affect its practical application as well as the aesthetics; keep in mind the purpose of the room and how your radiator can be most beneficial.

If you need any further clarification or reassurance, please do not hesitate to contact us on 01473 276686.