HVAC equipment — air conditioners, furnaces, heat pumps — is almost always rated in BTUs (British Thermal Units), a unit of heat energy, while your electricity bill and most modern energy planning is done in kilowatt-hours. This calculator converts between the two directly, which is the exact step most people get stuck on when trying to compare a unit's heating/cooling capacity against actual electricity costs.
The Conversion Factor
1 kWh = 3,412.14 BTU
So to convert BTU to kWh, divide by 3,412.14. To go the other direction, multiply kWh by 3,412.14.
Worked Example
A furnace rated to output 60,000 BTU/hour, running for 3 hours:
An Important Distinction: Heat Output vs. Electricity Consumed
This is where a lot of confusion happens, and it's worth being precise about. The BTU rating on an HVAC unit typically describes the heat energy moved or produced, not the electricity the unit draws from the wall. These are only the same number for pure resistive electric heat (where 1 kWh of electricity in produces roughly 3,412 BTU of heat out, a 1:1 efficiency).
For anything else — gas furnaces, heat pumps, air conditioners — the relationship is different:
- Gas furnaces convert fuel (not electricity) to heat, so their BTU rating relates to gas consumption, not kWh, except for the smaller electricity draw of the blower fan.
- Heat pumps and AC units move heat rather than generating it directly, and can deliver more heat energy (in BTU) than the electrical energy (in kWh) they consume — this ratio is called the COP (Coefficient of Performance) for heating or SEER/EER for cooling. A heat pump with a COP of 3 delivers roughly 3 kWh of heat for every 1 kWh of electricity it actually draws.
So: if you're trying to estimate your actual electric bill impact from an HVAC unit's BTU rating, you need the unit's efficiency rating (COP, SEER, or EER) — not just the BTU-to-kWh conversion factor alone.
Worked Example — Estimating Real Electricity Use
A heat pump rated at 24,000 BTU/hour output, with a COP of 3.2, running for 5 hours:
That's the number that actually shows up on your bill — noticeably less than the raw heat-output conversion alone would suggest.
Frequently Asked
How many kWh is a 12,000 BTU air conditioner?
12,000 BTU/hour of cooling ÷ 3,412.14 ≈ 3.52 kWh of cooling capacity per hour. Actual electricity drawn depends on the unit's EER/SEER rating — a more efficient unit uses fewer actual kWh to deliver that same 3.52 kWh of cooling.
Is BTU a measure of power or energy?
BTU alone is a unit of energy (like a joule or a kWh). BTU/hour (often just written as "BTU" on HVAC labels, which is technically imprecise) is a rate — a measure of power, equivalent to how kW relates to kWh.
Why do some regions use BTU and others use kW for HVAC?
It's largely a legacy/regional convention — the US and a few other countries commonly rate HVAC equipment in BTU/hour, while most of the rest of the world uses kW directly for the same specification.
For heat pump and space heater specific calculations, see the appliance energy calculator hub.
