The air conditioner comes on and shuts off in response to temperature, not humidity. A conditioner that is too large will not do a good job of reducing humidity, and a system that is too small will not cool the air sufficiently. DPS recommends buying a model with an EER of 10 or higher. Central air conditioning generally is more expensive and uses more energy than room units, but costs can be kept at a minimum by buying the right size, choosing a high efficiency system, and locating and maintaining the system properly. DPS recommends buying a system with a SEER of 12.5 or higher.
Good maintenance is important for proper operation of room and central air conditioners.
Replace or clean filters monthly and remove dirt, leaves, and debris from outside coils. More information on ways to keep cool with or without air conditioning is provided in a guide on Home Cooling available from the Energy Information Center.