Glossary · Heating, cooling & ventilation

BTU and BTU/h

Also called: BTU · BTUs · British thermal unit · British thermal units · BTU/h · BTU/hr

A unit of heat energy; BTU per hour (BTU/h) measures how fast a furnace, heat pump or air conditioner delivers heating or cooling.

What it means

One BTU is the heat needed to warm one pound of water by 1°F. Fuel energy is counted in BTU (or therms and MMBtu), while equipment capacity is given in BTU/h, for example a 60,000 BTU/h furnace or a 24,000 BTU/h (2-ton) heat pump. The metric equivalents are joules for energy and watts or kilowatts for capacity.

Why it matters in an audit

Comparing your home's calculated heat loss in BTU/h (see load calculation) with the equipment's rated capacity shows whether a system is sized correctly.

Typical numbers

Reference values with their sources. Your auditor’s report gives the figure for your own house.

What	Value	Source
Electricity (EIA)	1 kWh = 3,412 BTU	eia.gov ↗
Natural gas (EIA)	1 therm = 100,000 BTU; 1 cubic foot ≈ 1,036 BTU	eia.gov ↗
Metric (NIST)	1 BTU = 1,055 J; 1 BTU/h = 0.293 W	nist.gov ↗
Cooling ton (NIST)	12,000 BTU/h = 1 ton = 3.517 kW	nist.gov ↗

Sources

Learn more here

Sizing heating and cooling: the load calculation →

Related terms

Ton (of cooling) A unit of heating and cooling capacity: one ton equals 12,000 BTU per hour (3.5 kW), based on the cooling from melting a ton of ice in a day.
Therm The unit many US gas bills use: one therm is 100,000 BTU of heat energy, roughly the energy in 100 cubic feet of natural gas.
Kilowatt-hour (kWh) The unit on your electricity bill: one kilowatt-hour is 1,000 watts used for one hour, such as a 100-watt bulb left on for 10 hours.
Load calculation An engineering calculation of how much heating and cooling a house needs, room by room, used to size equipment correctly.
Oversizing Installing heating or cooling equipment with much more capacity than the house needs, usually from rules of thumb, not a load calculation.
kBtu and MMBtu (thousand and million BTU) Shorthand for large amounts of heat energy: kBtu is a thousand BTU and MMBtu is a million BTU, used to compare fuels and yearly energy use.
Kilowatt (kW) A rate of using or producing energy equal to 1,000 watts; running 1 kW for an hour uses 1 kilowatt-hour (kWh), the unit on your electricity bill.

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