Below is what MD Air Conditioning and Heating recommends for routine service, assuming you are not having any problems:
FALL SERVICE- We usually have special pricing on "Fall Checks" in October-November. This is the time to service heaters which are best to service just before the beginning of the heating season.
Gas Heaters- service yearly. We recommend carbon monoxide detectors for all homes with gas appliances.
SPRING CHECKS- We offer spring checks at a special price from March 1st thru April 15th. All units need service in the spring to insure proper operation for the upcomming summer heat.
A/C and Heat Pumps- It is best to have your A/C or Heat Pump serviced and cleaned every Spring. Your unit gets dirty with use and needs to be washed out yearly.
Filters-there are several types of filters. Some are good and some are not. A filter must fit correctly to work properly. Therefore, one of the easiest setups are to use a "Filter Grill" for your filter. This makes filter changing easy. If you don't have a filter grill, we would be glad to install one for you.
WE DO NOT RECOMMEND THE PLEATED FILTERS that are very common and expensive. They restrict the air too much causing other issues. The only time we recommend a pleated filter is if you have at least 250sq/in of return air per ton of air conditioning. Most (99.9%) do not have that much return.
WE DO RECOMMEND the cheap filters Walmart, Home Depot, Lowes and other stores sell. These filters cost less than $1.00 each. Some come in a 4 pack for $3-$4.00.
A filter must be changed every 2-4 weeks. More in the summer and less in the winter. If you have hard surface floors (tile, brick, wood, linoleum) you need to change your filter more. It is ok to change your filter weekly. If it is real dirty when you change it then change it sooner next time.
Gulf Coast Air Care has a good filter system, here is their link. www.gulfcoastaircare.com/