How to Convert kWh to BTU: Formula and Constant
A British Thermal Unit (BTU) is the amount of heat energy required to raise the temperature of one pound of water by one degree Fahrenheit (°F) at sea level. The exact physical relation between electrical and thermal units is:
For resistive electric heaters (which convert 100% of electricity into heat), a 1.5 kW electric room heater generates exactly: 1.5 kW × 1 hr × 3,412.14 BTU = 5,118.2 BTU of heat output per hour.
Air Conditioner Tonnage vs. BTU vs. Power Consumption
| AC Capacity (Tons) | Cooling Rate (BTU/hr) | Electrical Power Draw (kW) | Energy at 1 Hour (kWh) |
|---|---|---|---|
| 1.0 Ton | 12,000 BTU/hr | 0.9 – 1.1 kW | ~1.0 kWh |
| 1.5 Ton | 18,000 BTU/hr | 1.4 – 1.8 kW | ~1.5 – 1.8 kWh |
| 2.0 Ton | 24,000 BTU/hr | 2.0 – 2.4 kW | ~2.2 kWh |
Frequently Asked Questions: kWh and BTU
Why do AC units use BTU instead of kWh?
BTU measures cooling capacity (the rate at which heat is extracted from a room), while kWh measures the electrical energy consumed by the compressor and fans to accomplish that heat transfer. Heat pumps move 3 to 4 times more BTU of heat than the electrical energy they consume, thanks to the refrigeration cycle.
How many BTU is a 1.5 ton AC?
A 1.5-ton air conditioner provides 18,000 BTU per hour of cooling capacity. One refrigeration ton is historically defined as the rate of heat extraction needed to freeze 1 short ton of water in 24 hours, which equals 12,000 BTU/hour. Calculate your AC running costs on our AC kWh Calculator.
Is BTU per hour the same as kWh?
No. BTU per hour (BTU/h) is an instantaneous rate of power flow (like kW), whereas kWh is accumulated total energy over time. 1 kW of continuous power equates to 3,412.14 BTU/h of continuous thermal transfer.