Should You Cover Your AC Unit in the Winter?

Every fall, we get the same question from homeowners in Chattanooga: “Should I cover my outdoor AC unit for winter?” The short answer is no—and here’s exactly why.

Modern AC Units Are Built for the Outdoors

Your condenser is engineered to handle rain, snow, ice, and freezing temperatures year-round. The cabinet is made of weather-resistant steel or aluminum, and the coils are coated to resist corrosion. Covering it doesn’t protect it—it often hurts it.

Why Covering Is a Bad Idea

1. Trapped Moisture = Rust & Mold: A sealed cover turns your unit into a humid greenhouse. Condensation builds up inside, leading to rust on coils and electrical components.

2. Pests Move In: Mice, squirrels, and insects love dark, cozy spaces. A cover invites them to nest and chew wires—a repair bill you don’t want.

3. Blocked Airflow Hurts Performance: Even a “breathable” cover restricts airflow. In spring, restricted coils mean higher energy bills and early system failure.

🚨 HEAT PUMP OWNERS: NEVER COVER—NOT EVEN THE TOP

If your outdoor unit runs when your heat is on, you have a heat pump. These systems reverse in winter to pull heat from the air. Every 30–90 minutes, they enter a defrost cycle—melting ice on the coils with warm refrigerant.

• A plywood board or top cover blocks this process.

• Ice builds up → the unit strains → compressor fails ($1,500–$3,000 repair).

• Backup electric heat kicks in → $300+ electric bills.

Rule: Zero covering for heat pumps. Period.

What You Should Do Instead

1. Turn off power at the outdoor disconnect or breaker.

2. Clear debris—use a hose (on low) to rinse leaves and dirt from the fins.

3. Keep 2–3 feet clear around the unit (no shrubs, no snow piles).

4. Elevate if needed—in heavy snow areas, raise the unit 6–8 inches on a pad.

Optional (only for cooling-only ACs in heavy snow): A vented plywood top (not sealed) can prevent large ice buildup. But most Chattanoogans don’t need it.

The Bottom Line

Leave your AC or heat pump uncovered. A clean, open unit survives winter better—and saves you from costly spring surprises.