How to tell if you have a heat pump
A heat pump looks a lot like an air conditioner. Here are five quick checks to know which one you have.
5 ways to tell
- Does the outdoor unit run in winter? If the outdoor unit kicks on to heat your home in cold weather, it is a heat pump. An air conditioner sits idle in winter.
- Check the thermostat for "Emergency Heat" or "Aux Heat." Those settings (and an "EM HEAT" light) are unique to heat pumps.
- Look at the outdoor unit's label. A model number or nameplate that says "heat pump," or lists a HSPF/HSPF2 rating, confirms it. AC-only units list only SEER and have no heating rating.
- Find the reversing valve. A heat pump's outdoor unit has a brass reversing valve (a cylinder with several copper lines) near the compressor — an AC does not.
- Is there a separate furnace? If you have no gas furnace or the "furnace" is just an air handler with electric backup, you very likely have a heat pump.
What does a heat pump look like?
From the outside, a heat pump looks almost identical to a central air conditioner: a metal box (usually about 2–4 ft tall) on a pad beside the house, with a large fan on top and grille-covered sides. The visible giveaways are inside the cabinet — a brass reversing valve and extra refrigerant piping near the compressor — and on the rating plate, which lists a heating rating (HSPF/HSPF2) where an AC shows only SEER. Indoors you will find an air handler (not a fuel-burning furnace) and a thermostat with an "Em Heat" or "Aux" setting.
Why it matters
Knowing helps you operate it efficiently (avoid over-using emergency heat), maintain it correctly, and size a replacement. If you have a heat pump, our size and cost calculators can help you plan.
Frequently asked questions
How do I know if I have a heat pump or an AC?
The simplest test: if the outdoor unit runs to heat your home in winter, it is a heat pump. An AC only runs for cooling.
Does a heat pump have an emergency heat setting?
Yes — an "Emergency Heat" or "Aux Heat" option on the thermostat is a tell-tale sign of a heat pump.
What does a heat pump look like?
It looks almost identical to an air conditioner — an outdoor box with a fan — but it has a reversing valve and runs in winter.
Related
Sources & further reading
Educational guide, reviewed against US DOE & ENERGY STAR guidance and updated June 2026. Estimates only — not a substitute for a professional assessment or Manual J load calculation.