How to Install Home Air Conditioning Systems

Choose a unit with the highest available efficiency rating and the British thermal unit (BTU) count necessary for the room. Estimate the BTU needed by multiplying the room's square footage by 35. Account for additional heat in the room. The kitchen, for example, needs about 4,000 extra BTUs. For rooms occupied by more than two people, add 600 BTUs for each occupant beyond the initial two occupants.

Measure the window before going to the appliance store to make sure the A/C unit will fit the bottom section of the glass. The window glass covering the unit should slide up and down; otherwise the unit will not fit properly.

Choose the best window in the room for the unit. The ideal place is a window frame close to the center of the room, with outside shade for hot summer days and without obstructions like a bed or television nearby.

Prepare the frame for the unit. Slide the bottom glass up. Arrange a leveling piece - a shim or a scrap wood piece cut to size - on the sill, so that it provides a slight tilt for the unit's water drain. Attach the unit to the frame with screws, nails or staples.

Move the unit onto the sill. If the unit includes an accordion flap, fit the flap to the frame. Install any metal brackets included as well. Fasten the flap and/or brackets to the frame with screws, nails or staples. Close the window onto the unit.

Fill or cover any sections that do not have an airtight seal with weather strips.