To determine the number of BTUs (British Thermal Units) that you need to heat a 20×20 garage, you will need to calculate the heat loss of the space. The heat loss of a space is the amount of heat that the space loses to the surrounding environment. This will depend on factors such as the climate where you live, the insulation of the garage, and the size of the garage.
Once you have calculated the heat loss of your garage, you can use the following formula to determine the number of BTUs you need to heat the space:
BTUs = (Heat Loss * Hours of Operation * Temperature Rise) / (Efficiency of the Heater * 3.413)
For example, let’s say that your 20×20 garage has a heat loss of 30,000 BTUs per hour, you want to raise the temperature of the garage by 30 degrees Fahrenheit, and the efficiency of your heater is 75%. In this case, you would need a heater with a BTU rating of:
(30,000 BTUs/hr * 24 hrs/day * 30 degrees F) / (0.75 * 3.413) = 206,272 BTUs/day
This is just an example, and the actual BTU rating that you need may be different depending on your specific situation. It’s always a good idea to consult with a heating and cooling professional to determine the best size and type of heater for your needs.