Same cooling math, different heating story
For cooling, heat pumps and AC units are sized by BTU removal load — our BTU calculator applies to both. Heat pumps add reverse operation for winter; efficiency drops as outdoor temperature falls.
Mini-splits are almost always heat pumps today — one outdoor unit heats and cools a zone.
Climate and backup heat
See SEER ratings explained for efficiency shopping — higher SEER saves kWh over years, not first-season comfort.
Plan winter load with the heat pump cold climate calculator or furnace BTU calculator before you rip out working heat.
- Mild climates: heat pump often replaces furnace for moderate loads
- Cold climates: auxiliary heat strips or furnace backup may run below ~20°F
- Cooling-only window units: no heat — cheapest upfront, no winter value
- HSPF and SEER: read both on heat pump labels
Design temperature vs nameplate BTU
Nameplate heating BTU is often rated near 47°F. Your home’s design temperature may be 10°F, 0°F, or lower. Ask for capacity tables at that outdoor temp — that number decides backup heat, not the brochure headline.
Oversizing cooling to chase winter capacity causes sticky summer short-cycling. Right-size each season, then choose dual fuel or strips for the gap.