Cost: $200-$300, depending on where you live.
How often: At least once a year.
When: Spring or fall. Heating, ventilation and air conditioning, or HVAC, companies aren't as busy, and you're not in dire need of heat or air conditioning.
What an inspection might find: The reversing switch in the heat pump is broken. Cost to repair or replace: $100-$300. Letting it go results in no heat from the heat pump, and the system switches to a more expensive auxiliary heat. Potential savings: lower heating bills.
Bottom line: Terry Townsend of Townsend Engineering in Chattanooga, Tenn., and former president of the American Society of Heating, Refrigerating and Air-Conditioning Engineers said, "Remember, continual maintenance prolongs the life of the equipment. You're sitting there with an investment of thousands in your HVAC system and you're investing a few hundred dollars in maintenance."