Our electric fireplaces can function as supplemental heat sources for rooms up to 400 square feet. Most Built-in electric fireboxes can be hardwired to 240V power to heat a room up to 800 square feet, depending on product specifications. If more heat is necessary, our infrared electric fireboxes are capable of heating up to 1,000 square feet. These infrared units may be plugged into standard 120V household outlets.