What is a BTU per Hour?

BTU per hour (BTU/h or BTUh) is the standard rating for American heating, air-conditioning, and refrigeration system capacity. A window air conditioner is typically 5,000–12,000 BTU/h, central residential AC ranges 24,000–60,000 BTU/h, and commercial chillers reach 100,000–1,000,000+ BTU/h. The unit's persistence in HVAC reflects American engineering tradition: it directly links cooling/heating capacity to the BTU energy unit familiar in gas-fired equipment. 12,000 BTU/h equals 'one ton of refrigeration' (a unit derived from the heat needed to melt 1 ton of ice in 24 hours), so AC sizes are sometimes given in 'tons' (a 3-ton AC = 36,000 BTU/h). BTU/h relates to the watt (1 W ≈ 3.412 BTU/h), the kilowatt (1 kW ≈ 3,412 BTU/h), and the ton of refrigeration (12,000 BTU/h = 1 ton). Outside the US, kW is dominant for HVAC capacity.

Visual reference for how the btu per hour relates to other power units. Each row links to the full converter for that pair.

• US air conditioners and heat pumps
• US furnace and boiler ratings
• Some industrial heat-exchanger specs

• ✓1 BTU/h = 0.293 W; 3412 BTU/h = 1 kW.
• ✓12,000 BTU/h = 1 ton of refrigeration.
• ✓Tons of AC rating: divide BTU/h by 12,000.

• ✗Confusing BTU (energy) with BTU/h (power) — same abbreviation in ads.
• ✗Mixing tons of AC and tons of weight — different concepts.
• ✗Using BTU/h for non-HVAC contexts.