Different types of HVAC filters include electrostatic filters, fiberglass filters, and pleated filters. When buying an air filter for your AC unit, consider its MERV rating. Look for a thick filter, as thick filters often provide superior air cleaning and also last long. Consider the design of the filter and use different ratings to compare filter longevity, particulate-capturing efficiency, and pressure drop. Call South Placer Heating and Air at (916) 246-2089 for any help.