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HVAC Maintenance Schedule: What to Do and When
Your HVAC system is probably the most expensive thing in your house that you've never thought about until it stops working. A central air conditioning and heating system costs $6,000–$15,000 to replace, runs 24 hours a day in peak seasons, and has a straightforward maintenance schedule that most homeowners never follow.
Here's the complete picture: what you should be doing, when to do it, and what professional service actually covers.
Monthly: Filter Check and Replacement
This is the single highest-impact maintenance task for your HVAC system, and it costs $10–$30. A clogged filter restricts airflow, forcing the system to work harder. Over time, restricted airflow strains the blower motor, causes the heat exchanger to overheat (in heating mode), and can freeze the evaporator coil (in cooling mode). All of those failures are expensive.
How often to change it depends on filter type and household conditions:
1-inch filters: every 30–90 days
4-inch media filters: every 6–12 months
Households with pets or high dust: change more frequently
Vacation homes or filtered-air environments: can extend the interval
The right answer for your home is to pull the filter and look at it. If it's gray and visibly clogged, change it regardless of when you last changed it. If it's mostly clean, check again in 30 days.
Quarterly: Visual Inspection
Every three months, spend five minutes looking at your system. You're checking for:
Condensate drain line: The drain pan under the air handler should be dry. Standing water or water stains indicate a clogged drain line — a common cause of HVAC shutdown (many systems have a float switch that kills power if the pan fills). Clear the drain with a cup of distilled white vinegar poured into the drain line access port.
Outdoor condenser unit: Clear any vegetation within 2 feet. Check that the unit is level (minor settling is normal; significant tilt affects refrigerant distribution). Look for bent fins — a fin comb ($10 at any hardware store) straightens them and improves airflow.
Ductwork (accessible sections): Look for disconnected joints, gaps at connections, or signs of pest intrusion. Disconnected ductwork in an attic or crawl space is a major efficiency loss.
Annually: Professional Service (Spring for AC, Fall for Heat)
Annual professional maintenance is non-negotiable for any HVAC system you want to get full life out of. For a split system (separate furnace and AC), this means two service calls per year. For a heat pump (handles both heating and cooling), one thorough service call in spring or fall covers both.
What a professional tune-up covers:
Refrigerant level check and recharge if needed (low refrigerant indicates a leak that needs to be found and repaired)
Electrical connections: tightening, checking for corrosion
Capacitor check (capacitors are a common failure point and relatively inexpensive to replace proactively)
Blower motor lubrication and inspection
Heat exchanger inspection (critical safety check — cracks in the heat exchanger allow combustion gases into the living space)
Thermostat calibration
Coil cleaning — evaporator coil (inside) and condenser coil (outside)
Combustion analysis on gas furnaces
Cost: $80–$200 per visit. The service call pays for itself when it catches a $40 capacitor before it becomes an emergency weekend call-out at $400+.
What Your Inspection Report Tells You
If you bought your home with an inspection, the report contains specific information about your HVAC system: make, model, approximate age, and the inspector's assessment of condition. This changes your maintenance calculus significantly.
An HVAC system installed in 2015 and noted as "in good working condition" needs standard annual maintenance. A system noted as "approaching end of expected service life with rust at the heat exchanger" needs either immediate professional evaluation or early replacement planning. The generic schedule above applies to the first scenario — the second requires a different approach.
When to Consider Replacement
Rule of thumb from HVAC contractors: if the system is over 10 years old and a single repair exceeds 50% of replacement cost, replace it. A $1,500 compressor repair on a 14-year-old system is almost always worse economics than a new unit.
Signs you're approaching replacement territory:
Increasing energy bills without an obvious cause
Frequent repairs in the past 2–3 years
Inconsistent temperatures throughout the house
System runs constantly and can't maintain the set temperature
Age beyond expected lifespan (15–20 years for central AC, 20–30 for a well-maintained gas furnace)