Winterizing Your HVAC System
Winterizing your HVAC is mainly about protecting your AC during the off-season and ensuring your heating system is ready. Here is what actually matters and what common advice gets wrong.
Should You Cover Your Outdoor AC Unit?
This is the most common winterizing question -- and the answer is more nuanced than most people expect.
What many sources recommend: full top cover. A cover over the top of the condenser unit keeps out leaves, seeds, and debris that can accumulate in the unit over winter. If your area has heavy tree seed fall or cottonwood, a top cover can reduce spring cleaning work.
What you should NOT do: full-wrap cover. Wrapping the entire outdoor unit in a vinyl cover traps moisture inside, encourages rust, and creates ideal nesting habitat for mice and other animals that chew on wiring. A solid full wrap does more harm than good in most climates.
For heat pumps: do not cover them at all. Heat pumps operate in heating mode all winter. Never cover a heat pump outdoor unit -- it must remain accessible for airflow. If yours has an ice buildup problem, that is a system issue to address with a technician, not something to solve with a cover.
Winterizing the AC System
- Do a final visual inspection of the condenser unit before cold sets in -- clean out any debris from inside the unit before covering
- If you use a top cover, install it after the cooling season ends and before the first snowfall
- Disconnect the exterior AC disconnect switch (the metal box near the outdoor unit) in climates with very cold winters -- this prevents the system from accidentally starting on a warm winter day when outdoor temperatures could damage the compressor
- Check refrigerant lines -- if the insulation on the lines is deteriorating, have it replaced before another season of UV exposure degrades it further
Preparing the Heating System
- Replace the air filter before the heating season starts
- Schedule a professional furnace inspection in fall if you have not had one in the past 12 months
- Test the thermostat in HEAT mode on a mild fall day before cold weather arrives
- Check that CO detectors are working and batteries are fresh
- If you have a propane or oil system, check fuel levels before winter -- do not assume there is enough to last the season
Frequently Asked Questions
- Should I cover my AC unit in winter?
- A cover over the top of the unit (not a full wrap) can keep out debris in areas with heavy leaf or seed fall. Never use a full-wrap vinyl cover -- it traps moisture and encourages animal nesting. Never cover a heat pump -- it must remain accessible for winter heating operation.
- Do I need to winterize my central AC?
- In most climates, central AC units are designed to withstand winter temperatures without special preparation. The main tasks are: clear debris from around and inside the unit before winter, optionally add a top cover in high-debris areas, and make sure the system is off and the disconnect is open if the system might accidentally start on a warm winter day.
- What happens if I do not winterize my AC?
- Most modern AC units are designed to handle winter exposure without damage. The main risks of no winterization are debris accumulation inside the unit (reducible with a top cover) and accidental start-up in cold weather (preventable by opening the exterior disconnect). Full system failure from lack of winterizing is rare with modern equipment.
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