Our free Garage Heater Calculator takes the guesswork out of selecting a garage heater. Answer a few questions about your energy source and garage and the . This free calculator estimates the number of BTUs needed to heat or cool a house . the higher the BTU rating of an appliance, the greater the heating capacity. Getting the right size heater for your garage saves money twice. . Fortunately, the calculation for correctly sizing a heater is simple when you take accurate . NOTE: Many factors will effect the garage temperature. For example bringing in two cars that have been outside in the cold for hours will increase the time . May 16, 2008 – Garage Heater Calculator recommends garage heaters based on a . we thought it was a cool tool to contribute to the greater community.”. Dec 26, 2017 – The general guideline when sizing heaters is 10 watts for every square foot of space. For example, the NewAir G56 Electric Garage Heater has . A heater’s physical size has little to do with its heating abilities. The heater type, such as radiant or forced air, the British Thermal Unit (BTU) output, your garage’s . 20°F outside. 10°F outside. 0°F outside. 1 car, 8 ft ceiling up to 450 sq ft. 3,700 watts. 4,400 watts. 5,150 watts. 1 car, 10 ft ceiling up to 450 sq ft. 4,050 watts. The best place to start when considering the purchase of a space heater for your home is to calculate the BTUs. Use our free heating BTU calculator! Keep from going stir crazy in the winter by heating your garage so you can work out there year-round. We’ll show you two ways to keep your garage warm.