$5K
Average AC replacement
Split system, 2.5 ton
$300
Annual tune-up cost
vs. $3,000+ emergency repair
15 yrs
HVAC enters high-wear phase
Compressor and heat exchanger risk
47%
Of home energy use
Is heating and cooling
System Types
Most homes have one of three configurations. Knowing yours is the foundation of understanding maintenance.
Split systems
The most common configuration in American homes. A split system has two units — an outdoor condenser/compressor and an indoor air handler with the evaporator coil. Most split systems provide both heating (via heat pump or gas furnace) and cooling.
Heat pumps
A heat pump is a split system that can move heat in both directions — extracting heat from outside air in winter to heat the home, and running in reverse in summer to cool. In cold climates they're often paired with a gas furnace backup — this is called a dual-fuel system.
Ductless mini-splits
An outdoor unit connects to one or more indoor air handlers mounted on walls or ceilings, with no duct system. They're highly efficient and allow zone control, but each air handler requires individual maintenance.
Key Components
Every component has its own failure mode — knowing them helps you have better conversations with technicians.
Compressor
The compressor is the heart of the cooling system and the most expensive component to replace. A failed compressor in an older system often makes replacement more cost-effective than repair.
Capacitors and contactors
Capacitors start the compressor and fan motors. Contactors are the switches that control power flow. Both are high-failure components — and both are inexpensive parts that cause expensive symptoms when they fail. Replacement is typically $150-$400.
Refrigerant
Your system should not need refrigerant added under normal operation. Refrigerant doesn't get used up — it circulates in a closed loop. If a technician says you're low on refrigerant, that means you have a leak. Adding refrigerant without finding and fixing the leak is a waste of money.
Condensate drain
The evaporator coil removes humidity from the air, and that water drains through a condensate line. Algae and mold grow in this line and block it. Pouring a cup of diluted bleach down the drain line once a year prevents this.
The 5,000 rule
Failure Timeline
New system
Change filter every 90 days. Register warranty. No major maintenance needed.
Mid life
Annual tune-ups become important. Capacitors and contactors can start wearing. Confirm drain line is clear every season.
Watch phase
Refrigerant leaks become more common. Compressor efficiency begins declining. Keep service records current.
High wear
Apply the 5,000 rule to every repair estimate. Compressor failure risk is real. Begin budgeting for replacement.
End of life
Replace proactively before an emergency failure in peak summer or winter.
Maintenance & Tune-Ups
Annual tune-ups are the single most cost-effective maintenance action for HVAC systems. A good tune-up takes 60-90 minutes and covers everything in the system, not just a filter check.
Filter maintenance
This is the most important thing you can do yourself. A clogged filter restricts airflow, which makes the system work harder, which increases wear on every component. Check your filter every 30 days. Replace when visibly dirty — usually every 60-90 days for 1" filters.
Repair vs. Replace
Questions to ask your contractor
"Is this a refrigerant leak, and if so, where is it?"
Adding refrigerant without finding the leak is not a repair — it's a temporary fix. Any leak should be located and repaired.
"What is the SEER rating of the replacement unit you're recommending?"
Higher SEER units cost more upfront but less to operate. Current minimum is 14 SEER; 16+ is worth considering if you run the system heavily.
"Can I see the heat exchanger issue you're describing?"
Heat exchanger cracks are real but the claim is occasionally used dishonestly. A legitimate technician can show you the crack in person or via camera.