How heat pump sizing works
A heat pump both cools and heats, so it has two loads to meet. The calculator works out each from your square footage, climate zone, ceiling height and insulation.
- Warm and mild climates (zones 1–3). The heat pump is sized to the cooling load. Its heating capacity covers the short, mild winters.
- Cool and cold climates (zones 4–5). The heating load is bigger. The calculator sizes up modestly, to no more than 25% above the cooling load, and shows how much backup heat covers the rest.
Tons = max(cooling BTU, heating BTU capped at 1.25 × cooling) ÷ 12,000
Heat pump size chart
| Home size | Warm climate | Mild climate | Cold climate |
|---|
| 1,000 sq ft | 2.5 ton | 2 ton | 2 ton |
| 1,200 sq ft | 3 ton | 2.5 ton | 2.5 ton |
| 1,500 sq ft | 3.5 ton | 3 ton | 3 ton |
| 1,800 sq ft | 4 ton | 4 ton | 4 ton |
| 2,000 sq ft | 5 ton | 4 ton | 4 ton |
| 2,400 sq ft | 2 systems | 5 ton | 5 ton |
Pool heat pumps are different. They're sized by pool surface area and temperature rise, not house square footage.
Common questions
What size heat pump do I need for a 1,500 sq ft house?
About 3 tons in a mild climate and 3.5 tons in a warm southern climate. In a cold northern climate a 3-ton cold-climate heat pump is common, with backup heat for the coldest days.
Should a heat pump be sized for heating or cooling?
In warm and mild climates, size it for cooling — the heating load is smaller and easily covered. In cold climates the heating load is larger, so installers often size up modestly and add electric or gas backup heat rather than buying a unit that is far too big for summer.
Do I need backup heat with a heat pump?
In zones 1–3 usually not. In zones 4–5, standard heat pumps lose capacity below freezing, so most homes add electric strips or keep a furnace as backup. Cold-climate heat pumps reduce how much backup you need.
Can I size a heat pump by ZIP code?
Yes. Enter your ZIP code and the calculator sets your climate zone, which changes both the cooling and the heating load.
How many square feet does a 3-ton heat pump cover?
Roughly 1,300 to 1,800 square feet, depending on climate and insulation.