Btu/hr to Watts Converter: Formula & Examples

This calculator converts power from British thermal units per hour (Btu/hr) to watts (W). You enter the power in Btu/hr, and you get the equivalent in watts instantly, along with the formula used. The conversion is a simple multiplication: 1 Btu/hr equals 0.29307107 watts.

Formula

The conversion between Btu/hr and watts is defined by the relationship:

P(W) = P(Btu/hr) × 0.29307107

Where:

• P(W) is the power in watts.
• P(Btu/hr) is the power in British thermal units per hour.

The factor 0.29307107 comes from the definition of the British thermal unit: 1 Btu is the amount of heat required to raise the temperature of 1 pound of water by 1°F at sea level. When spread over one hour, that equals 0.29307107 joules per second, which is the same as watts.

Worked Example

Using the default value of 10,000 Btu/hr:

1. Start with the formula: P(W) = P(Btu/hr) × 0.29307107
2. Plug in the value: P(W) = 10,000 × 0.29307107
3. Multiply: P(W) = 2,930.7107
4. Round to two decimal places: 2,930.71 W

So 10,000 Btu/hr is equal to approximately 2,931 watts. The calculator shows this result rounded to two decimals.

Why Convert Between Btu/hr and Watts?

Btu/hr is the standard unit for heating and cooling capacity in the United States. Air conditioners, furnaces, water heaters, and heat pumps are rated in Btu/hr. Watts, on the other hand, are the universal SI unit for power and are used for electrical devices, solar panels, and most scientific and international applications. When you need to compare a gas furnace with an electric heater, or when you’re calculating electrical load from a heating appliance, you must convert between these units.

For example, a typical window air conditioner might be rated at 12,000 Btu/hr. To know its electrical power consumption (in watts), you’d convert: 12,000 × 0.29307107 ≈ 3,517 W. That’s the power it draws when running, not the cooling output. This distinction is crucial for sizing generators, circuits, and solar systems.

How to Read the Result

The result in watts tells you the equivalent rate of energy transfer. One watt equals one joule per second. So if a device is rated at 5,000 Btu/hr, it transfers 5,000 × 0.29307107 ≈ 1,465 J of heat every second. This is the same regardless of whether the device is electric, gas, or solar—it’s a pure unit conversion.

Be aware that for heating and cooling equipment, the Btu/hr rating is often the heating or cooling capacity, not the electrical input. For example, a heat pump with a 36,000 Btu/hr cooling capacity might only draw 3,000–4,000 watts of electricity. The conversion above gives you the thermal power, not the electrical consumption. To find electrical consumption, you need the efficiency rating (like SEER or HSPF) or the nameplate wattage.

Common Mistakes and Misconceptions

• Confusing Btu with Btu/hr: A Btu is a unit of energy, while Btu/hr is a unit of power. You cannot convert Btu directly to watts; you must have a time component. Always check that your value is per hour.
• Using the wrong conversion factor: Some sources use 0.293, others 0.29307107. The difference is negligible for most practical purposes, but for precise engineering work, use the full factor.
• Forgetting to convert hours: If your value is in Btu per minute or per day, you must first convert to per hour. For example, 1,000 Btu/min = 60,000 Btu/hr.
• Assuming watts equals Btu/hr: They are different units. A 1,500 W space heater produces about 5,118 Btu/hr of heat, not 1,500 Btu/hr.

Practical Applications

Here are common situations where you’ll need this conversion:

• Comparing heaters: An electric space heater is rated in watts, while a gas heater is rated in Btu/hr. To compare their heat output, convert the gas heater to watts or the electric heater to Btu/hr.
• Sizing a generator: If you have a furnace with a 60,000 Btu/hr input, you need a generator that can supply at least 60,000 × 0.29307107 ≈ 17,584 W, though the actual electrical draw is lower due to efficiency.
• Solar panel sizing: Solar panels are rated in watts. If you want to replace a 5,000 Btu/hr air conditioner with solar, you need at least 5,000 × 0.29307107 ≈ 1,465 W of solar capacity (plus battery storage for non-sunny hours).
• International equipment: When buying appliances from overseas, you may see kW ratings. 1 kW = 1,000 W = 3,412 Btu/hr. This is the reverse conversion.

Limits of the Conversion

This conversion is exact for pure unit conversion. However, it does not account for efficiency. A gas furnace rated at 80,000 Btu/hr input will not deliver 80,000 Btu/hr of heat to your home—it might deliver only 64,000 Btu/hr (80% efficiency). Similarly, an air conditioner’s Btu/hr rating is its cooling capacity, not its electrical power draw. Always read the label to see whether the rating is input or output.

Also, the definition of the Btu varies slightly (there are different standards like the International Table Btu and the thermochemical Btu), but the difference is less than 0.05%, so the factor 0.29307107 is accurate for all practical purposes.

Frequently Asked Questions

How many watts is 12,000 Btu/hr?

12,000 Btu/hr × 0.29307107 = 3,516.85 W. So a 12,000 Btu/hr air conditioner has a cooling capacity of about 3,517 watts. This is often called a “one-ton” unit in HVAC terminology.

How do I convert watts to Btu/hr?

Use the inverse: multiply watts by 3.41214163. For example, 1,500 W × 3.41214163 = 5,118 Btu/hr. This is how you compare an electric heater to a gas heater.

Is Btu/hr the same as horsepower?

No. Horsepower is a different unit of power. 1 horsepower = 2,544.43 Btu/hr. This is sometimes used for older mechanical equipment, but for heating/cooling, Btu/hr is standard.

What is the difference between Btu and Btu/hr?

Btu is a unit of energy (like a calorie or joule). Btu/hr is a unit of power (like a watt). A furnace might burn 100,000 Btu in an hour, so its power is 100,000 Btu/hr. If it runs for 2 hours, it consumes 200,000 Btu of energy.

Why do air conditioners use Btu/hr instead of watts?

Historically, the HVAC industry in the US adopted Btu/hr because it relates to the heat content of fuels and the cooling effect of ice. It’s a convention that persists even though watts are more universal. For electrical engineers, watts are more intuitive, so conversions are common.

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in btu | Power | Btu/hr | 10000 | 0
out watts | Power | W | btu * 0.29307107 | 2