25,000 BTU is almost always a heater rating. Gas wall furnaces, vent-free wall heaters and ceiling-hung propane or natural gas garage heaters are sold at 25,000 BTU; air conditioners jump from 24,000 to 30,000. As a heater it covers about 620 sq ft of insulated space in a moderate climate, 830 in a hot one and 450 in a cold one.
Garages are the usual question. In a poorly insulated garage the same heater covers about 520 sq ft in a moderate climate and 370 in a cold one. A two-car garage is 400 to 576 sq ft, so 25,000 BTU is about right in moderate climates and short in cold ones, where 30,000 to 40,000 BTU is the usual pick. A tall ceiling pushes it further: a 10 ft ceiling adds 25 percent to the load.
Gas ratings need one more check, because input is not output. A vented heater rated 25,000 BTU input at 80 percent efficiency delivers about 20,000 BTU/hr of heat, which covers about 500 sq ft of insulated space in a moderate climate rather than 620. Vent-free heaters put nearly all of their input into the room, but they also add moisture and are not allowed everywhere, so check local code first.
An electric heater with 25,000 BTU output would need about 7,300 W, over 30 A at 240 V, which is why electric garage heaters top out around 7,500 W. Converted, 25,000 BTU/hr is 7.33 kW or 7,327 W. As cooling it would cover about 1,250 sq ft, just over 2 tons.
How many square feet a 25,000 BTU air conditioner cools
Largest room the unit keeps up with, rounded down to the nearest 10 sq ft. Two occupants, 8 ft ceiling and moderate climate unless the row says otherwise.
| Room | Cools up to |
|---|---|
| Shaded, good insulation | 1,540 sq ft |
| Average room (baseline) | 1,250 sq ft |
| Very sunny, poor insulation | 980 sq ft |
| Hot climate, very sunny | 1,030 sq ft |
| 10 ft ceiling | 1,000 sq ft |
| 4 people instead of 2 | 1,190 sq ft |
| Kitchen in the space | 1,050 sq ft |
How many square feet 25,000 BTU of heat covers
By climate and insulation. For a gas heater, use its output rating (input × efficiency).
| Climate | Poor insulation | Average insulation | Good insulation |
|---|---|---|---|
| hot | 690 sq ft | 830 sq ft | 980 sq ft |
| moderate | 520 sq ft | 620 sq ft | 730 sq ft |
| cold | 370 sq ft | 450 sq ft | 530 sq ft |
25,000 BTU in kW, watts and tons
| Kilowatts | 7.33 kW |
| Watts | 7,327 W |
| Tons of cooling | 2.08 tons |
| Power an AC this size draws (EER 11) | about 2,273 W, 9.9 A at 230 V |
| Power an electric heater needs for this output | 7,327 W, 30.5 A at 240 V |
kW and watts here are heat output, the number on the box. An air conditioner moves that much heat while drawing far less electricity; an electric heater draws exactly as much as it puts out.
25,000 BTU questions
How many square feet will a 25,000 BTU heater heat?
About 620 sq ft of insulated space in a moderate climate, 830 in a hot one and 450 in a cold one. For a vented gas heater, use its output (about 80 percent of input), which lowers those figures.
Is a 25,000 BTU heater enough for a 2-car garage?
In a moderate climate, usually yes: a poorly insulated garage needs about 48 BTU/hr per sq ft, so 25,000 BTU covers about 520 sq ft. In a cold climate it covers only about 370 sq ft, so step up to 30,000 to 40,000 BTU.
What is 25,000 BTU in kW?
7.33 kW, or 7,327 W. Divide BTU/hr by 3,412.