One of the least costly, most efficient ways to keep your HVAC system in good shape is to regularly replace or clean (depending on type) the air filter. An HVAC filter does keep some particles out of your home but its primary purpose is protecting the equipment itself from clogging and overheating.
Dirty filters shorten the life of an HVAC system and force it to work harder (which costs you more money). Whether they are disposable or permanent, air filters have a standard rating – MERV, for minimum efficiency reporting value. MERV ratings range from 1 to 16; the higher the number, the smaller the particles the filter will stop.
Types of residential HVAC filters
Disposable fiberglass filters
Made of spun fiberglass, this is the least expensive filter and the kind with the lowest MERV rating. The frame is usually heavy cardboard and the layered fiberglass may be reinforced with wire mesh. Flat, disposable fiberglass filters do little to clean the air and they’ll keep only the largest particles from clogging your equipment.
Disposable pleated filters
Made from polyester or cotton paper, pleated filters can remove some small particles but need frequent changing. Filter manufacturers recommend changing pleated filters every three months, but you’ll want to change them more often if you have pets, children, allergies and/or generate a lot of dust because they have more surface area to trap particles.
Polyester filter media pads
These are washable filters that have higher MERV ratings than fiberglass filters, hold more dust and have more resistance. They often are used to replace fiberglass filters.
Electrostatic filters can be disposable or permanent. Both contain self-charging fibers that attract and trap small particles. In popular sizes, a permanent electrostatic filter is a cost-effective option because it is machine-washable and can be reused for several years.
Additional HVAC filter tips
- Change inexpensive flat filters at least once a month.
- If you hold a used filter up to the light and cannot see the light, replace it.
- Window AC units often have foam filters that can be washed.
- Let all washable HVAC filters dry completely before reinstalling them.
- Filters with MERV ratings of 11 or higher are considered efficient.
A high efficiency particulate air filter (HEPA) will remove nearly all particles from the air – when the fan is on – but replacing HEPA filters can be expensive. Also, not all HVAC systems can accommodate HEPA filters. Make sure yours can before installing one.
Related HVAC information
How to change an AC filter