Quick reference
Garage Heater BTU Chart
A quick comparison for common garages. Every value below uses the same sizing engine as the calculator: average insulation and the stated temperature rise.
| Garage | Example dimensions | 20 F rise | 30 F rise | 40 F rise | 50 F rise |
|---|---|---|---|---|---|
| 1-car | 12 x 20 x 8 ft | 5,000 BTU/hr 5,000 BTU/hr standard size | 7,500 BTU/hr 7,500 BTU/hr standard size | 10,000 BTU/hr 10,000 BTU/hr standard size | 13,000 BTU/hr 15,000 BTU/hr standard size |
| 2-car | 24 x 24 x 8 ft | 12,500 BTU/hr 12,500 BTU/hr standard size | 18,500 BTU/hr 20,000 BTU/hr standard size | 24,500 BTU/hr 25,000 BTU/hr standard size | 30,500 BTU/hr 35,000 BTU/hr standard size |
| 3-car | 32 x 24 x 8 ft | 16,500 BTU/hr 20,000 BTU/hr standard size | 24,500 BTU/hr 25,000 BTU/hr standard size | 32,500 BTU/hr 35,000 BTU/hr standard size | 41,000 BTU/hr 45,000 BTU/hr standard size |
How to read the chart
A 40 F temperature rise means warming a garage from 20 F outside to 60 F inside. Use a higher column for colder climates or a warmer target temperature. Every value assumes average insulation.
Adjusting for insulation
Relative to the average rows above: a poorly insulated or uninsulated garage needs about 50% more capacity, a well insulated garage about 25% less, and a tightly sealed, fully insulated garage about 40% less. These ratios come straight from the insulation factors documented on the methodology page, and the calculator applies them for you.
Why the chart is not a final answer
Charts cannot see your garage doors, window area, drafts, ceiling height, or the coldest temperature you expect. Use the calculator before buying so the inputs reflect your actual garage.