Do You Know When To Change Your Air Conditioner Filter?

by Don Munn

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Do You Know When To Change Your Air Filter

One of the most important things that you can do to keep your air conditioner or furnace working at maximum efficiency , is change the filter every one to six months. I know, that’s not very helpful information. Unfortunately it’s hard to be exact for many reasons so lets cover some of things that you will need to consider when scheduling filter changes in your home. If you use a very efficient air filter, it may need to be changed every month. If you use a very inefficient filter you may only need to replace it every six months.

Every house is different and there are many factors that determine how often your heating and air conditioning filters should be replaced. If you wait too long operating efficiency begins to decline, as efficiency drops operating costs increase. Changing your air filter more often than necessary is like throwing money away. Considering the cost of some filters that will add up to a lot of money over your life time.

Some Cautions About Using Inefficient Filters

Cheap inefficient panel filters can cause problems with air conditioners over time and are best avoided. The dust that does not get collected by your filter gets redistributed back into your home. That can be bothersome but the biggest concern with this is the dust that collects on the fan, blower motor and evaporator coil of your air conditioner. This can cause maintenance problems and impact equipment performance which leads to service calls and that just costs more money.

A Good Reason To Use Efficient Filters

If you are an allergy sufferer or have other health concerns, efficient filters are a better choice for you. Filters with high MERV ratings or high efficiency ratings will remove more household allergens from the air and allergic reactions may be reduced.

Some Things To Consider

  • If you use a very efficient air filter it will probably need to be changed monthly. This is because efficient filters collect a lot more dust than inefficient filters. For example a MERV 12 pleated filter, HEPA filters and electrostatic filters should be changed or cleaned monthly.
  • Economy panel filters that you can get at many hardware stores are very inefficient and will not have to be changed very often. These are very poor quality and I don’t recommend them.
  • If you live in a location that is very dusty you will need to change your filter more often than if you live in a low dust area.
  • Air filters generally need to be changed more often in summer months than in winter months when the ground is covered with snow.
  • Equipment that does not operate continuously will not require as many filter changes as equipment that is always operating. Between heating and cooling seasons are typically low usage times.

What About Filter Change Reminders

Many thermostats have filter change indicators to remind you to change your ac or furnace filter at predetermined intervals and some can be programmed to remind you at whatever interval you want. These are ok for reminders but don’t have much real value because they don’t indicate when the filter is actually becoming dirty enough to restrict air flow and begin effecting unit operation.

A Couple of Better Options for Home Owners

Remove your air filter monthly for inspection. When it is dirty enough and you change it, write the date down on the side of your air handler, duct system or where ever your filter is installed. After a year of doing this you will have established a very good guide for when to change your air conditioner filter or furnace filter.

Your best option is to use an air filter change indicator. These devices are inexpensive and mount on the side of your air handler. As your filter becomes dirty an indicator needle moves up a scale from “Filter Is Clean” to “Change Filter”. These devices work on negative air pressure so you eliminate the guesswork and you get the most from you air conditioner filter or furnace filter.

Don Munn About Don Munn
Don has been working in the HVAC industry for more than 25 years and shares his experience and knowledge on this site. If you find the information presented here helpful please use the buttons below and share with your friends.



{ 2 comments… read them below or add one }

Pete Barri

I use my air condition 1 (one) hr. Every day. My brother uses his A/c 24 hrs per day . Should we both change the filter once every month?

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Don Munn

Hi Pete,

There are a lot of variables to consider but in your case, assuming you use a pleated filter, I would recommend changing your filter every 3 to 6 months. For your brother I would recommend every 1 to 3 months.

This also can change from winter to summer because there are typically more allergens and dust during summer months. Remove your filter and check it every month, if it is a bit dirty but no noticeable build up it may be good for another month. If you are noticing dust build up then replace it.

The ideal time to replace the filter is when it is beginning to have an impact on air flow. This way you are getting the maximum use from your filter and not replacing it too early. You should read my post about air filter change indicators linked to above for more information on that.

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