What BTU means
A BTU, or British thermal unit, is a unit of heat. Furnace output, air conditioner capacity and fuel energy are all stated in BTUs, usually per hour.
Also called British thermal unit, Btu.
Where it matters on a HVAC job
Every sizing conversation runs in BTUs: the load calculation says how many the house needs, the equipment label says how many the unit delivers. When a homeowner compares quotes, show both numbers side by side so the bigger unit is not mistaken for the better one.
The numbers, with sources
- One BTU is the heat needed to raise one pound of water by 1 degree Fahrenheit. (US Energy Information Administration)
- One kilowatt-hour equals 3,412 BTU, and one cubic foot of natural gas holds about 1,036 BTU. (US Energy Information Administration)
What it costs
The furnace replacement cost guide has the typical job at $4,800 and the usual range at $2,800 to $7,250. The guide shows its sources and what moves the price. The btu heating calculator prices a job line by line.
Work it out
- Free calculator: BTU heating calculator
- Cost guide: Furnace replacement cost
- Licensing: HVAC license rules by state
- Tools, templates and guides: Free HVAC resources
Sources: US Energy Information Administration, British thermal units (Btu). Checked October 9, 2026.