Heat Storm Phoenix Infrared Space Heater and Sei Furniture Calvert Electric Carved Fireplace Wattage and British Thermal Units (Btu) indicate how large of a space a heater can effectively warm up.

As an example, 1,500 watts equal 5,115 Btu, which amounts to a little over 250 square feet. This electric radiant heater has two heat settings, with an adjustable thermostat that maintains the ...