Changing your HVAC air filter is one of the highest-impact, lowest-cost things you can do to keep your heating and cooling system running efficiently. A clogged filter restricts airflow, forcing your system to work harder, driving up energy bills, and accelerating wear on the blower motor and heat exchanger. Most homeowners in the Denver area should plan on changing their filter every 1–3 months depending on filter type, household size, and how much dust, pet dander, or wildfire smoke is in the air.

Step-by-Step: How to Change Your Air Filter

The process takes about five minutes once you know what you’re doing. Start by turning off your thermostat — you don’t want the system pulling air while the filter slot is open. Then locate the filter. In most homes it’s either in a return air grille on a wall or ceiling (usually a large grille with a latch or screws), or it slides into a slot on the side or bottom of the air handler unit itself. Some homes have both.

Slide or pull the old filter out and note the direction of the airflow arrow printed on the frame — you’ll need to orient the new filter the same way. Airflow runs from the return side toward the blower, so the arrow should point toward the unit (away from the return grille). Drop the new filter in with the arrow pointing the correct direction, close the access panel or grille, and turn the thermostat back on. That’s it.

Choosing the Right Filter for Your Home

Filters are rated by MERV (Minimum Efficiency Reporting Value) — the higher the number, the finer the particles it captures. A MERV 1–4 fiberglass panel filter catches large debris but does little for air quality. MERV 8 pleated filters are the practical minimum for most homes — they capture dust, pollen, mold spores, and pet dander effectively. MERV 11–13 filters add finer particles including some bacteria and smoke particles, which is particularly relevant during Colorado wildfire season when smoke can drift into the metro for days at a time.

Resist the temptation to jump to the highest MERV rating available. Filters above MERV 13 can restrict airflow significantly in systems not designed for them, potentially causing the same problems as a clogged filter. If you want superior filtration, a whole-home air purification system installed inside the ductwork is a better solution than a very restrictive panel filter.

How Often Should Denver-Area Homeowners Change Filters?

  • Basic 1-inch fiberglass filters: every 30 days
  • Standard 1-inch pleated MERV 8 filters: every 60–90 days
  • Thicker 4–5 inch media filters: every 6–12 months (check the manufacturer’s spec)
  • Homes with pets or multiple people: shorten the interval by 30 days
  • During wildfire smoke events: check the filter more frequently — smoke loads filters much faster than normal dust

What Happens If You Skip Filter Changes?

A heavily restricted filter causes your blower motor to strain trying to pull air through. Over time this leads to overheating, which can trip the high-limit safety switch and shut down your furnace in the middle of a Colorado cold snap. In summer, restricted airflow reduces how effectively the evaporator coil can absorb heat, lowering cooling capacity and sometimes causing the coil to freeze. A frozen evaporator coil will eventually damage the compressor — one of the most expensive components in the whole system.

Beyond equipment damage, a clogged filter stops doing its job of keeping dust off the evaporator coil and blower wheel. Dirty coils and blower wheels are less efficient, harder to clean, and can become breeding grounds for mold when moisture is present.

Filter Changes Are Not a Substitute for Professional Maintenance

Changing your filter regularly is essential, but it doesn’t replace annual professional maintenance. A tune-up includes cleaning the evaporator and condenser coils, checking refrigerant charge, testing electrical components, lubricating moving parts, and calibrating the system — things a filter change simply doesn’t address. Pairing good filter habits with annual service keeps your system running as efficiently as possible and catches problems before they become breakdowns.

Done offers AC maintenance and furnace maintenance throughout the Denver metro. If you’re unsure what filter type is right for your system, or if you’d like to explore whole-home air quality options, visit our indoor air quality page or contact Done and we’ll point you in the right direction.