How to Install a Window Air Conditioner

Window units provide instant relief during heatwaves, but they require a precise setup to avoid noise, leaks, or accidental falls. A properly installed unit isn't just about wedging it in; it's about creating a rigid, airtight barrier that keeps the humidity out and the cool air circulating efficiently through your living space. Take your time with the balance of the unit. The weight needs to be supported primarily by the window sill, not just the sliding sash. If you get the tilt and the seal right, the machine will run quieter and use significantly less electricity throughout the summer months.

1. Create a Clean, Level Base. Clean the window sill thoroughly to ensure a flat, stable surface for the unit. Remove any existing window screens and ensure the lower sash moves freely.
2. Anchor the External Support. If your unit requires an external support bracket, secure it to the exterior siding or sill according to the manufacturer's weight specifications. This bracket takes the load off your window frame, preventing structural damage.
3. Seat the Unit Securely. With a partner, center the air conditioner on the sill, ensuring the bottom rail sits securely against the sash track. Slide the unit forward until the external rail locks onto the sill.
4. Lock Sash to Unit Frame. Lower the window sash until it rests firmly on top of the air conditioner's housing. Drive the included locking screws through the sash and into the unit frame to lock it in place.
5. Extend Panels Wall-to-Wall. Slide the accordion side panels out until they meet the edges of the window frame. Secure the panels using the provided mounting hardware or screws.
6. Block All Thermal Leaks. Place the adhesive foam strip across the top of the lower sash to block the gap between the upper and lower window panes. Use additional foam or rigid insulation board to fill any remaining voids around the side panels.