Many variables affect how much space an electric fireplace will heat.
- House age
- Type of construction
- Condition and size of windows and doors
- Sidewall and ceiling insulation levels
- Southern Orientation
- Prevailing winter winds
And obviously, a home in Northern Canada will have different heating requirements than a house in the Carolinas.
Many people use electric fireplaces as supplemental heat, not the primary heat source. Generally, an electric fireplace can comfortably heat most well-insulated rooms in colder climates, up to 250–300 square feet. If your electric fireplace is in a larger room, you can expect heating within a 10 - 15 feet radius.
The heating element in most electric fireplaces, stoves, and inserts is 1500 or 1800 watts. Respectively, this translates to 5000 and 6140 BTUs of heat.