Preventive Maintenance keeps your system running at the highest efficiency possible and will help prevent those unwanted EMERGENCY NO HEAT or NO A/C calls. Preventative Maintenance for your Heating and Cooling systems is very much like the regular maintenance you do for your car by changing the oil and filter. If you never change the oil in your car, you will get away with it for some time but eventually, the engine will ping and have permanent damage.  To keep your heating and cooling system well maintained, the recommended service is once per year per system. Ideally, heating systems should get annual maintenance before the heating season begins in the fall and A/C systems in the spring.