A 1,500 watt heater producing 5,100 BTUs can heat 150 square feet. That’s equivalent to a 10-by-15 foot room, an 11-by-14 or one sized to 12-by-12 1/2 feet with a standard 8-foot ceiling.

No energy is wasted. Most space heaters generate 1,500 watts or about 5,118 BTU’s (British Thermal Units). That is about the amount of energy needed to heatone small room. … No matter how elaborate the cabinet that holds it, electricheating is the same.