Heat Pump Size Calculator
Enter your home details to get a recommended BTU range and tonnage for your climate zone.
Frequently Asked Questions
What size heat pump do I need?
Heat pump size depends on your home's square footage, climate zone, insulation quality, and layout. A simplified Manual J calculation uses roughly 25–60 BTU per square foot depending on your IECC climate zone — from 25 BTU/sqft in hot climates to 60 BTU/sqft in subarctic zones. Insulation quality can adjust this by ±20%. A licensed contractor should perform a full Manual J load calculation before final equipment selection.
How many BTU per square foot for a heat pump?
BTU per square foot varies by IECC climate zone: Zone 1–2 (hot/humid South): 25–30 BTU/sqft. Zone 3 (warm — Atlanta, Dallas): 30–35 BTU/sqft. Zone 4 (mixed — DC, Kansas City): 35–40 BTU/sqft. Zone 5 (cool — Chicago, Denver): 40–45 BTU/sqft. Zone 6–7 (cold — Minneapolis, Montana): 45–55 BTU/sqft. Zone 8 (subarctic Alaska): 55–60 BTU/sqft. These are starting estimates before adjusting for insulation and layout.
What happens if my heat pump is too small?
An undersized heat pump runs continuously trying to meet the heating or cooling load, resulting in high energy bills, poor comfort, and early equipment failure. On the coldest days it will fail to reach your setpoint temperature. In cooling mode it will not adequately dehumidify, leaving the home feeling clammy.
What happens if my heat pump is too big?
An oversized heat pump short-cycles — it reaches setpoint quickly, shuts off, and then restarts frequently. Short cycling causes excessive wear on the compressor, poor humidity control in summer, temperature swings, and reduced efficiency. Bigger is not better for heat pumps. Right-sizing is critical.
Estimate only. Results are based on general Manual J simplified guidelines and IECC 2021 climate zone data. Actual results may vary based on site conditions, ceiling height, window-to-wall ratio, ductwork efficiency, and local utility rates. Final sizing requires a Manual J load calculation performed by a licensed HVAC contractor.