HVAC Maintenance Checklist: What to Do Every Season

A homeowner I help out called me one February morning saying her furnace was making a "smell like a hair dryer." She had not changed the filter in 14 months. The filter was so packed that the blower had been pulling against high static pressure for a full year, the motor was running hot, and the bearings were on the verge of seizing. A $12 filter and a $185 tune-up would have prevented a $620 motor replacement.

This is what skipped HVAC maintenance actually costs. Below is the schedule I follow on my own house and recommend to neighbors. It is split into what to do yourself (monthly, seasonal) and what to leave to a pro (twice a year).

Monthly: 5 Minutes, No Tools

Check the Air Filter

The single most important thing you can do. Pull it out, hold it up to a light, and if you cannot clearly see the bulb through the filter, replace it. For standard 1-inch filters, plan on a fresh one every 1 to 3 months. Pleated 4 to 5-inch media filters last 6 to 12 months. Homes with multiple pets or smokers, check every month.

Quick math: A clogged filter increases system runtime by 5 to 15 percent (per U.S. Department of Energy). On a $200/month summer electric bill, that is $10 to $30 a month, more than the cost of a year of filters.

Walk Around the Outdoor Unit

Quick visual inspection. Anything growing within 2 feet? Trim it. Anything stacked against it (lawn furniture, kid's toys, recycle bins)? Move it. Cottonwood season or grass-clipping season? Knock loose debris off with a gloved hand or a soft brush.

Listen and Notice

Pay attention to anything that sounds different. New rattles, grinding, hissing, or clicking are early warnings. So is a system that suddenly runs much longer than it used to. The earlier you catch a change, the cheaper the fix.

Spring (March or April): AC Prep

DIY Tasks

1. Replace the air filter. Start the cooling season clean.
2. Rinse the outdoor condenser coil. Shut power at the disconnect, brush off loose debris, and rinse the fins from the inside out with a garden hose on a gentle setting. Never use a pressure washer. This single task can recover 15 to 25 percent of lost capacity on a coil that hasn't been cleaned in years.
3. Pour a cup of distilled vinegar down the condensate drain line. Find the PVC pipe coming off the indoor unit, locate the cleanout (usually a T-fitting with a removable cap), and pour. This dissolves algae before it causes a backed-up drain in July (which can flood your ceiling if the unit is in the attic).
4. Clear 2 feet of space around the outdoor unit. Trim shrubs, move planters, remove anything obstructing airflow.
5. Test your thermostat batteries. A dying battery causes intermittent shutoffs that look like compressor problems.

Schedule a Professional AC Tune-Up ($100 to $200)

A real tune-up should include:

• Refrigerant pressure and superheat/subcool measurements
• Capacitor microfarad reading (compared to nameplate spec)
• Contactor inspection (pitting, burning)
• Amp draw on compressor and fan motor
• Temperature drop across the evaporator coil (should be 16 to 22 degrees F)
• Condensate drain flush
• Indoor coil inspection
• Electrical connection tightening

Insider tip: Ask the technician to leave a written report with actual numbers (capacitor µF, amp draw, refrigerant pressures, temperature split). A "tune-up" without measured values is just a glorified visual inspection. If they push hard on $400+ "premium service plans" or refuse to itemize what they did, find another contractor next year.

Summer (June to August): Mid-Season Care

1. Check filter monthly during heavy use.
2. Keep the outdoor unit clear of cottonwood, grass clippings, and yard debris.
3. Watch for ice on refrigerant lines, water around the indoor unit, or longer-than-normal runtimes.
4. If your system is over 10 years old, run our free age check and consider whether replacement should be on your 12-month radar.

Fall (September or October): Furnace Prep

DIY Tasks

1. Replace the air filter. Heating season needs a fresh one too.
2. Clear flue and intake vents. For high-efficiency furnaces with PVC vents on the exterior wall, make sure they aren't blocked by leaves, snow, or bird nests.
3. Test smoke and carbon monoxide detectors. CO is invisible and odorless; cracked heat exchangers and improperly venting furnaces are the most common residential CO sources. Replace batteries and replace any detector older than its expiration date (most last 7 to 10 years). The CDC's carbon monoxide page has solid guidance.
4. Run the heat for 10 minutes. Better to discover a problem in September than during the first hard freeze. Expect a brief burning smell as dust burns off the heat exchanger.
5. Reverse ceiling fans to clockwise (low speed). Pushes warm air down from the ceiling.

Schedule a Professional Furnace Tune-Up ($100 to $200)

A real furnace tune-up should include:

• Heat exchanger inspection (visual and combustion-analyzer reading for CO leaks)
• Burner cleaning and ignition test
• Flue pipe inspection
• Gas pressure measurement (manifold pressure)
• Blower motor inspection and lubrication if applicable
• Limit switch and flame sensor cleaning
• Combustion analysis (CO, CO2, oxygen levels)

If your furnace is gas, the heat exchanger inspection is the single most important step. A cracked heat exchanger can leak carbon monoxide into your home's air supply. Per the EPA, residential CO poisoning sends thousands of Americans to the ER each year, and most cases trace back to combustion appliances.

Winter (December to February): Hands-Off

1. Continue monthly filter checks.
2. Make sure outdoor heat pump units are clear of snow and ice; brush snow off the top so the fan can pull air freely.
3. If you have a high-efficiency furnace, check that the PVC vents on the exterior wall haven't gotten blocked by snow drifts or ice.
4. Don't close more than 20 percent of your supply vents. Closing too many starves the blower and damages the system.

Year-Round Maintenance Cost vs. Repair Cost

Maintenance Task	Annual Cost	Cost If Skipped
Filter changes (4 to 12/year)	$20 to $80	$300 to $900 (blower motor or frozen coil)
Spring AC tune-up	$100 to $200	$400 to $1,500 (refrigerant leak or capacitor failure)
Fall furnace tune-up	$100 to $200	$200 to $2,500 (igniter, control board, heat exchanger)
Condensate drain treatment	$5	$200 to $3,000 (water damage cleanup)
Coil cleaning	$0 (DIY) to $150 (pro)	$150 to $300/year in extra electricity
Total annual	$225 to $635	$1,250 to $8,200 (worst case)

Service Plans: Worth It or Not?

Most HVAC contractors sell annual maintenance plans for $150 to $300. A typical plan includes a spring AC tune-up, a fall furnace tune-up, priority scheduling, and 10 to 20 percent off repairs.

The math: two tune-ups individually cost $200 to $400 if you call cold. A maintenance plan bundles them at $150 to $300 and bumps you to the front of the line in July. The priority scheduling alone can save you a day or two of misery in peak season. I have a service plan on my own house, and the priority dispatch has paid for it in the years it mattered.

Signs Maintenance Has Been Skipped Too Long

• Bills creeping up year over year for the same usage
• The system runs noticeably longer than it used to
• Uneven temperatures between rooms that used to be even
• New smells (musty, hot, electrical)
• Ice on refrigerant lines or on the indoor coil
• Water on the floor near the indoor unit
• Short cycling (turns on and off every few minutes)

If you see two or more of these, schedule a tune-up immediately, then read our guide on why your AC isn't cooling.

Quick Seasonal Calendar

Month	Task
March or April	Schedule AC tune-up, replace filter, rinse condenser, vinegar in drain
June to August	Monthly filter check, keep outdoor unit clear, watch for warning signs
September or October	Schedule furnace tune-up, replace filter, test CO detectors, run heat 10 min
December to February	Monthly filter check, clear snow from outdoor units, don't close vents

Bottom Line

HVAC equipment is mechanical and runs more hours per year than your car. It needs the same kind of routine attention. A few minutes a month and two tune-ups a year is the difference between a system that lasts 18 to 20 years and one that limps to 11. Run our free serial-number age tool to see where your system sits, and the ENERGY STAR maintenance checklist is a great printable backup.