Secret Behind Changing Air Filter: Central AC Filter Buying Guide

Your central air conditioner’s air filter is one of the system’s most important components affecting equipment maintenance, preservation of indoor air quality (IAQ), and efficient operation of your unit. All central A/C air filters should be changed at least every three months, although in many cases, it is recommended to do so at monthly intervals. Selecting the best filter to meet the needs of your household doesn’t have to be complicated; by reviewing the MERV (minimum efficiency reporting value) ratings, you’ll be able to determine which level of filtration is necessary in your situation. Changing of the filter itself is typically very straightforward and can be completed by most homeowners.


Benefits of Air Filters: Most Homeowners Don’t Know

  • While regular replacement of your air filter certainly does have a significant effect on IAQ, these filters are in place primarily to protect the inner workings of your air conditioner.
  • Before reaching the unit’s evaporator coils and moving parts like the fan and blower motor, all air gets a chance to first pass through the air filter, protecting these components from dirt, dust, and debris. Since the evaporator coils act as a heat exchanger, any material which reduces the amount of contact between the coils and the air forces the system to work harder;clean evaporator coils allow your unit to run for a shorter duration of time while still adequately cooling the air, minimizing energy consumption.
  • Additionally, the longevity of your air conditioner is maximized when its interior components are kept clean, as freely moving parts undergo far less stress than those that are dirty.

How Often Should I Change It?

Experts recommend changing a central A/C filter once every three months at a minimum, increasing the frequency to monthly intervals during the peak cooling season or in any home with pets or household members who have allergies, asthma, etc. A filter that has taken on a dark color and appears “clogged” is certainly in need of replacement; a monthly check is an excellent maintenance step for all central air conditioners and will help keep your ductwork clean while improving your home’s IAQ.

Select a Filter That Meets Your Needs

Air filters are manufactured from a variety of materials and are rated to indicate the size and percentage of particulates they remove from the air. You’ll find the following available in most local home improvement stores and/or online:filterchart

  • Fiberglass filters are the least expensive types of filters and are generally just a thin panel of woven material. They are often used in rental facilities and are available with MERV ratings between one and four, meaning they only remove the largest of airborne particles. Designed solely for the interior components of your air conditioner, these filters are generally not recommended as they will not improve IAQ and may not provide adequate equipment protection.
  •  Pleated filters are the next step up from thin fiberglass, providing a MERV rating between six and eight while still being quite affordable. The smaller pore sizes and greater surface area of these filters will help improve IAQ by removing a greater percentage of allergens, dust, dirt, lint, etc. In households without pets or respiratory sufferers, these filters are often the preferred choice as they offer adequate equipment protection while maintaining IAQ at a reasonable level.
  • Electrostatic filters carry an electrical charge that attracts airborne particulates, allowing them to capture and remove a much greater percentage of contaminants. Typically rated with a MERV value around 10, these filters are excellent in households with pets, smokers, or sensitive individuals that require a higher level of IAQ.
  • Permanent electrostatic filters offer many of the same advantages of disposable versions but can last up to eight years with regular cleaning, making them a very economical option. Their MERV ratings are often in the eight to 10 range.
  • High efficiency pleated filters are available with MERV ratings up to 16, although 13 is generally considered sufficient even in households with highly sensitive people. These filters will remove a large percentage of bacteria and some viruses from the air; those with ratings between 14 and 16 are even useful in hospital settings. Above MERV 13, air filters tend to restrict airflow within the system and can actually increase energy usage, meaning they are not ideally suited for household use.

Where is My Air Filter? How to Size and How to Replace?

Air filters are often located directly behind the large intake vent that is usually close to your thermostat; in some cases, you’ll find the filter in a slot contained within your air handler. Make sure to turn off the power or flip the breaker to “off” before checking your air filter in order to protect yourself and your equipment.

Careful measurement of your filter is a good way to avoid the headache of a return trip to the store or an online exchange that requires return shipping. The length and width of your replacement filter will have to match the old one, but you may or may not choose a filter of the same depth. Filters with higher MERV ratings tend to be thicker to provide a greater surface area to collect particulates, so if your old filter is the thin fiberglass type or just isn’t giving you the filtration level you’d prefer, chances are your new one will have a greater depth. For rectangular filters, the shorter number of length and width is listed first; manufacturers typically round numbers up to the nearest whole number, so if your filter measures 16.5 x 19.5 x 1 inches, you’ll be looking for a 17 x 20 x 1 inch filter (unless you choose to upgrade to a thicker filter with a higher MERV rating).

Once you’ve located and measured your old filter and have a new one ready to go, the actual replacement process is typically very straightforward. Cut the power to your unit, then undo the fasteners holding the front grate in place, or open the slot or housing containing the old filter. Remove the dirty filter with case so as to prevent dust and debris from being scattered, then carefully replace it with the new one. Close and re-fasten the housing/grate, turn the power back on, and you’re done.

Central AC Filter Price

For those of you comfortable with online shopping, you’ll find numerous sources selling single or multi-pack air filters in your exact size and MERV preference, often at a lower price than local stores. There are also plenty of local home improvement stores that stock a wide variety of sizes and styles of air filters. Expect to pay around $30-$40 online for a pack of six 1″ deep filters, many of which are rated MERV 6 or higher. Thicker filters with MERV ratings around 13 often cost $30 or more each, although cost does go down if you buy in bulk. Local prices tend to be a bit higher and you’ll have a smaller number of options from which to choose, but you’ll be able to change your air filter that same day instead of waiting on your online shipment.

Professionals Are Available to Help When You Need Them

In some cases, it may be difficult to locate or remove an old filter; if you find yourself in need of assistance, don’t hesitate to contact a professional HVAC technician. Once you watch a professional remove and change your old filter, chances are you’ll feel confident enough to do it yourself the next time, and in the long run, you’ll save significant amounts of money with reduced energy costs and an extended lifespan of your air conditioner.

Images Source:;

Leave a Comment Protection Status