Maintenance - Filters
Although you have probably heard it a million times before, changing your air filter regularly can greatly reduce your operating and maintenance costs on both air-conditioning and heating.

Clean air filters allow for a greater volume of air to circulate over the coils. More air flowing over the coils means shorter operating time and reduced operating costs. If clean air or allergies are of concern to you, consider electronic air cleaners which operate on electricity. These filters are 97% effective in removing air-borne contaminants; low operating costs and easy maintenance make them an excellent choice in managing dust and allergies.

There are also media or HEPA filters, which do an excellent job. They are 35-99% effective while standard air filters are 4-12% effective.