Don't overload extension cords by plugging in appliances that draw a total of more watts than the rating of the cord. Use special, heavy duty extension cords for high wattage appliances such as air conditioners, portable electric heaters, and freezers. When using outdoor tools and appliances, use only extension cords labeled for outdoor use.
Change the filters regularly. Dirty filters restrict air flow, reducing efficiency and worse case, can cause the evaporator to ice up. Disposable fiberglass filters should replaced. Electrostatic or electronic filters need to be washed regularly.