BTU to Watts Calculator

A BTU to watts calculator converts a BTU per hour rating into watts using the factor 0.29307107. Multiplying the rating by that factor gives the watts directly. For a 12,000 BTU/hr unit, the result is 3,516.85 W, or about 3.5 kW. The figure is rated output, not the electricity the unit draws.

Last reviewed September 2026Method & sources Report an error

Power

3,516.85 W

Breakdown
Power	3,516.85 W

How to Calculate BTU to Watts

Multiplying BTU per hour by 0.29307107 gives the equivalent power in watts. That factor is exact, since 1 BTU (International Table) equals 1,055.05585262 joules and there are 3,600 seconds in an hour (1,055.05585262 ÷ 3,600 = 0.29307107 W per BTU/hr).

Example: 12,000 BTU/hr air conditioner (1 ton of cooling capacity)

A 12,000 BTU/hr air conditioner (1 ton of cooling capacity): Power: 12,000 × 0.29307107 = 3,516.85 W (about 3.5 kW)

What Is BTU to Watts?

A BTU to watts calculator converts a heating or cooling appliance's BTU per hour rating into watts. BTU/hr is the standard US unit for furnaces, air conditioners, and space heaters, while watts are the standard international power unit. The conversion is useful for comparing a US-rated appliance against a metric specification, or for understanding its electrical draw relative to other watt-rated devices.

BTU to Watts: Pros and Cons

Pros

Uses the exact conversion factor derived from the precise BTU-to-joule definition, not a rounded approximation
Useful for comparing US BTU-rated equipment against metric watt or kilowatt specifications
Works for any BTU/hr rating, from a small space heater to a large central system

Cons

This is a rated capacity conversion, not the appliance's actual electrical power draw. An air conditioner's electrical input wattage is typically much lower than its BTU/hr cooling output, since it moves heat rather than generating it directly. See its EER or SEER rating for that relationship.
Doesn't distinguish heating output from cooling output. Both use the same BTU/hr-to-watts conversion, but they represent different kinds of equipment

Frequently Asked Questions

How do I convert BTU to watts?

Multiply BTU per hour by 0.29307107. A 12,000 BTU/hr unit equals 12,000 × 0.29307107 = 3,516.85 W.

Is BTU/hr the same as watts?

They're both units of power (energy per time), but from different measurement systems. BTU/hr is the traditional US unit for heating/cooling equipment, while watts is the standard international (SI) unit. They convert directly via a fixed exact factor.

Does a 12,000 BTU air conditioner use 3,517 watts of electricity?

No. That figure is its cooling output capacity, not its electrical power draw. An air conditioner moves heat rather than generating it, so its actual electrical input is typically a fraction of its BTU/hr output rating. Check the unit's EER or SEER efficiency rating to estimate actual electrical consumption.

How do I convert watts back to BTU?

Divide by 0.29307107 (or multiply by about 3.412). 1,000 W is about 1,000 ÷ 0.29307107 ≈ 3,412 BTU/hr.

How many watts is 1 ton of air conditioning?

About 3,517 W (or roughly 3.5 kW). Since 1 ton equals 12,000 BTU/hr, 12,000 × 0.29307107 ≈ 3,516.85 W.

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