Size a space heater by BTU for the room you want to heat.
Heaters are sized in BTUs using the room volume, a local insulation factor and the temperature rise desired. Watts convert to electric heater ratings. An undersized heater runs forever without warming the room, while an oversized one cycles and wastes energy, so matching BTU to volume is key.
Heater BTU Sizing
BTU/hr = volume x (insulation/10) x temp rise x 1.1
BTU/hr = volume x (insulation/10) x temp rise x 1.1 Heaters are sized in BTUs using the room volume, a local insulation factor and the temperature rise desired. Watts convert to electric heater ratings.
An undersized heater runs forever without warming the room, while an oversized one cycles and wastes energy, so matching BTU to volume is key.
This calculator takes 4 inputs: Room area, Ceiling height, Insulation factor, Desired temp rise. The pre-filled defaults are a realistic starting point — replace them with figures from your own environment for a result you can act on.