What size heat pump do I need?
Short answer
A 1,500 square foot home with average insulation needs about 4 tons (45,000 BTU) in a moderate climate, 3.5 tons in a mild one and 4.5 tons in a cold one. One ton is 12,000 BTU per hour.
Work it out for your numbers
Heat pump size
4 tons
- Capacity needed
- 45,000 BTU per hour
- Exact tons
- 3.75 tons
Heat pump size by home size and climate
| Home size | Mild (zones 1–3) | Moderate (zone 4) | Cold (zones 5–7) |
|---|---|---|---|
| 1,000 sq ft | 2.5 tons | 2.5 tons | 3 tons |
| 1,500 sq ft | 3.5 tons | 4 tons | 4.5 tons |
| 2,000 sq ft | 4.5 tons | 5 tons | 6 tons* |
| 2,500 sq ft | 5.5 tons* | 6.5 tons* | 7.5 tons* |
Average insulation, rounded up to the next half ton. *Residential heat pumps top out at 5 tons, so larger loads usually mean two systems or a zoned setup.
How the estimate works
Floor area times about 25 BTU per square foot in mild climates, 30 in moderate and 35 in cold ones, where the heat pump has to keep up with winter heating rather than just summer cooling. Then divide by 12,000 for tons and round up to the half-ton steps heat pumps are sold in.
Cold climates
Standard heat pumps lose capacity as it gets colder. If your winters drop well below freezing, look for a cold-climate model rated to keep most of its capacity at 5°F, or plan on backup heat such as electric strips or your existing furnace.
Sizing matters more than with a furnace
An oversized heat pump runs in short cycles, which in summer means it cools the air without running long enough to pull out humidity. Ask for a Manual J load calculation before you sign, and compare it with these numbers.
Single rooms and mini-splits
Ductless mini-splits are sized per room or zone. For one room, the AC BTU calculator or heater size calculator is a better fit.
Common questions
How many square feet does a 3 ton heat pump cover?
Roughly 1,200 square feet in a moderate climate and up to about 1,450 in a mild one, with average insulation.
How many BTU is a ton?
12,000 BTU per hour. A 3-ton heat pump is 36,000 BTU.
Can a heat pump heat my house in winter?
Yes, in most US climates. In very cold areas, choose a cold-climate model or keep backup heat for the coldest days.
Updated October 29, 2026. Figures are estimates for planning. Check product labels and local codes before you buy or build.