Can I Run AC in Cold Weather?
Running a traditional central air conditioner when outdoor temperatures are below 60 degrees F can cause problems. Heat pumps are different -- they are designed to operate in cold weather in heating mode. Here is what you need to know.
Standard Central AC in Cold Weather
Traditional air conditioners (cooling only, not heat pumps) are not designed to operate below about 60-65 degrees F outdoor temperature. Here is why: refrigerant pressure and viscosity change significantly with temperature. Below 60 degrees F, most standard AC systems will:
- Run with refrigerant at pressures outside the design range, stressing the compressor
- Experience oil return problems (compressor oil may not circulate properly in very cold conditions)
- Risk freezing the evaporator coil if the system runs long enough on a cold day
Operating a standard AC unit below 60 degrees F regularly can cause compressor damage. Most manufacturers void the compressor warranty if the unit is operated below their minimum ambient temperature rating.
Heat Pumps in Cold Weather
Heat pumps are designed to operate in cold weather -- that is one of their primary functions. In heating mode, a heat pump extracts heat from outdoor air and moves it inside. Standard heat pumps work down to about 35-40 degrees F before efficiency drops significantly. Cold-climate heat pumps are rated to -13 degrees F or lower.
If your system is a heat pump (you can check by finding the reversing valve in the outdoor unit, or looking at the thermostat for an "EM HEAT" setting), running it in cold weather for heating is entirely normal and expected.
Why Someone Might Try Running AC in Cold Weather
Common reasons: dehumidifying a basement or crawlspace in shoulder seasons, testing the system before summer, or a hot room in a home where other rooms are cool. For dehumidification in cold weather, a dedicated dehumidifier is a better tool than running the AC. For spot cooling a single room, a window unit or portable AC may handle this better than running the central system below its rated temperature range.
Frequently Asked Questions
- Can you run AC when it is cold outside?
- Standard AC units should not be run below 60-65 degrees F outdoor temperature. Operating below this range risks compressor damage from refrigerant pressure issues and oil circulation problems. Heat pumps are different -- they are designed to run in cold weather and operate in heating mode.
- What temperature is too cold to run AC?
- Most central air conditioners should not be operated below 60-65 degrees F outdoor temperature. Check your system's manual or manufacturer specifications for the exact minimum ambient temperature. Cold-climate heat pumps can operate in heating mode at much lower temperatures (as low as -13 to -22 degrees F).
- Can I run my heat pump in cold weather?
- Yes. Heat pumps are designed to operate in cold weather. In heating mode, a standard heat pump works effectively down to about 35-40 degrees F. Cold-climate heat pumps operate down to -13 to -22 degrees F. Running your heat pump in winter for heating is normal and expected.
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