kWh vs BTU: How to Convert and When to Use Each

6 min read•June 9, 2026•Reviewed: June 9, 2026

✓Reviewed by Apex Conversion Editorial Team · Last reviewed June 9, 2026

Kilowatt-hours (kWh) and BTU measure the same physical quantity — energy — but they grew up in different industries. The kWh is the universal unit of electrical energy: your utility bill, your EV battery, and your solar production report all use it. The BTU is the workhorse of American heating and cooling: furnaces, air conditioners, heat pumps, and water heaters are all rated in BTU or BTU per hour.

Anyone comparing an electric heat pump against a gas furnace, sizing an air conditioner, or reading both an electricity bill (kWh) and a gas bill (therms = 100,000 BTU) needs to move between these units. The conversion is a single fixed factor: 1 kWh = 3,412.14 BTU.

The Conversion Formula

kWh → BTU:  BTU = kWh × 3,412.14
BTU → kWh:  kWh = BTU ÷ 3,412.14

Quick mental estimate: kWh × 3,400 ≈ BTU

Common values:
   1 kWh  =  3,412 BTU
   5 kWh  = 17,061 BTU
  10 kWh  = 34,121 BTU
  29.3 kWh = 100,000 BTU = 1 therm

HVAC capacity (BTU/hr → kW):
  12,000 BTU/hr (1 ton)  = 3.52 kW
  24,000 BTU/hr (2 tons) = 7.03 kW
  36,000 BTU/hr (3 tons) = 10.55 kW

Energy vs. Power: The BTU/hr Distinction

The most common mistake when converting is confusing energy with power. A BTU is an amount of energy; BTU per hour (BTU/hr) is a rate of energy flow — power. Air conditioner ratings like '12,000 BTU' are shorthand for 12,000 BTU/hr, which converts to kilowatts (a power unit), not kilowatt-hours. A 12,000 BTU/hr unit delivers 3.52 kW of cooling.

Crucially, an air conditioner's cooling output is not its electricity consumption. A 12,000 BTU/hr unit with an EER of 10 draws only 1,200 W of electricity while moving 12,000 BTU/hr of heat — heat pumps and AC units move heat rather than generate it, so they deliver more thermal energy than the electrical energy they consume.

Comparing Gas and Electric Heating Costs

Converting both fuels to the same unit reveals true heating costs. Natural gas is billed in therms (100,000 BTU = 29.3 kWh). If gas costs $1.20 per therm, the energy price is $1.20 ÷ 29.3 = $0.041 per kWh of heat. If electricity costs $0.13 per kWh, electric resistance heating costs more than three times as much per unit of heat delivered.

Heat pumps change the math: a heat pump with a coefficient of performance (COP) of 3 delivers 3 kWh of heat per 1 kWh of electricity, bringing the effective cost down to $0.043 per kWh of heat — competitive with gas. This is exactly the comparison the kWh↔BTU conversion exists to enable.

Frequently Asked Questions

How many BTU is 1 kWh?

1 kWh = 3,412.14 BTU. Both are energy units; the factor comes from their joule definitions (3,600,000 J ÷ 1,055.06 J).

Is a 12,000 BTU air conditioner the same as 3.5 kWh?

Not quite — 12,000 BTU of energy equals 3.52 kWh, but an AC rating means 12,000 BTU per hour, which is a power of 3.52 kW. The unit consumes far less electricity than that (typically 1.0–1.5 kW) because it moves heat rather than generating it.

What is a therm and how does it relate to kWh?

A therm is the US natural gas billing unit: 1 therm = 100,000 BTU = 29.3 kWh. To compare gas and electricity prices, divide the price per therm by 29.3 to get the equivalent price per kWh.

Why does the US use BTU while Europe uses kW for heating?

The BTU predates SI and became embedded in American HVAC manufacturing and building codes. European equipment is rated in kilowatts. The equipment is identical — a 24,000 BTU/hr US unit and a 7 kW European unit have the same capacity.

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