99.9% efficient. The Mr. Heater 25,000 BTU Liquid Propane Gas garage heater offers. Whether you use it in your garage to keep your cars warm or in your shop to keep the work force busy and comfortable, the Mr. Heater Garage heater transfers almost all of the fuel it burns directly into clean, safe, radiant heat. Utilizing a unique power pile thermocouple to control the valve, there is no electricity required. Just hook-up the included milivolt thermostat with the appropriate wire – not included – then mount the heater to the wall and make the gas connection, then you are ready to go. Clean. Safe, Radiant Heat whenever you need it.