The general consensus among HVAC professionals is that you should replace your furnace filter every 90 days or every three months. However, this may vary depending on the thickness of the filter. Thicker filters have more room to capture dirt and dust, so they don't need to be changed as often. For 3- and 4-inch filters, plan a replacement approximately every six to nine months.
If you have larger 5- or 6-inch filters, you'll need to change them every nine to 12 months. In most cases, you should replace the filter at least every three months, even in summer. If you can't seem to remember to do it, a good rule of thumb is to change the furnace filter every time the seasons change. Generally, most air filter manufacturers and HVAC companies recommend changing the air filter every 90 days or 3 months. This may differ depending on the location of your home (e.g. dry and dusty climates), if you have pets and the age of your system and equipment.
If you have pets in the house, you should consider changing the filter every 60 days or 2 months, and for households with multiple pets or people with allergies or respiratory conditions, we recommend changing the filter every 20 to 45 days. Vacation homes or vacant homes that don't have much use can usually wait to change filters every 9-12 months. The air cleaner and boiler filter replacement cycle is also affected by air outside and inside your home. It's a general recommendation to change your home's air filter every 30 days when using less expensive fiberglass filters. Not many homeowners set their calendars for the next furnace filter replacement, but it's an essential step in keeping their heating and cooling system in top shape. Although furnace filters aren't designed to improve air quality, it's an accident that many of the things the filter prevents from entering your HVAC system also improve the air quality inside your home. Let's go through the basics of your furnace filter and determine exactly how often you need to change it.
The filters are designed to trap dust and airborne particles as air passes through the filter into the furnace system. If you're a pet owner, you'll want to change the air filter every 2 months, especially when winter turns to spring and summer to fall. As you check, gently vacuum the inlet side of the filter to help extend filter life and improve efficiency between changes. Without this air circulation, your system will produce heat, but it will remain contained in the furnace and will never heat your home. When the filter is clogged, it is more difficult for the furnace to draw in air, causing it to work harder and consume more energy.
Using an air filter with a MERV rating higher than recommended by the manufacturer of your furnace or air conditioner may impair its performance. If the fan in your heater is on constantly, you will need to change the filter every month; having it turned on sometimes will be every two months; never having it turned on may be every three months. Your furnace owner's manual will specify the best MERV rating for your furnace and, in general, filters with a MERV rating of 6 to 9 should be changed every 90 days, while those with a MERV rating of 10 to 12 should be changed every 60 days. In short, your furnace filter traps dirt, dust, allergens and other contaminants so they don't flow into the heating and cooling system (and don't breathe them in). It is usually located directly on the front or side of the furnace unit, but refer to the manual if you can't find it. If your furniture fills with dust soon after cleaning the house, the furnace filter could become clogged and no longer effectively remove dust from the air.