When should you replace an AC unit?

Replace an AC unit when 3 tests point to replacement: the unit is more than 10 years old, repairs are frequent and energy bills are rising. According to U.S. Department of Energy research from the Federal Energy Management Program, December 2024, the average residential central air conditioner life modeled for the hot-dry region, which includes California, is 25 years.

Key takeaways

Check the age

ENERGY STAR advises considering a replacement when a heat pump or air conditioner is more than 10 years old.

Compare repair and replacement cost

the $5,000 rule multiplies the age of the unit by the repair cost.

Weigh the system type

a ductless mini-split needs no ducts and a heat pump heats and cools with 1 system.

Choose the size

the AC size depends on the home size, the insulation and the sun exposure.

How long does an AC unit last?

The modeled average life of a residential central air conditioner in California is 25 years. According to ENERGY STAR research from the U.S. Environmental Protection Agency and the U.S. Department of Energy, a heat pump or air conditioner more than 10 years old that needs frequent repairs while energy bills rise is a candidate for replacement.

Should an AC unit be repaired or replaced?

The $5,000 rule is a rule of thumb: multiply the age of the unit in years by the repair cost, and a result above $5,000 points to replacement. The rule is a quick filter, not an industry standard. The cost factors of repair are explained on How Much Does HVAC Cost in San Diego?

Which AC brands are installed in San Diego homes?

The table lists the warranty terms of 3 AC brands from the manufacturer pages. Compare any brand by SEER2, warranty length, local service and parts availability.

Brand	Warranty terms	Source
Trane	Base limited warranty of 5 years on the compressor, the outdoor coil and parts; 10 years when the unit is registered within 60 days of installation; labor is not covered	Trane warranty page
Lennox	Compressor and components for 5 to 10 years depending on the model; a 3-year labor coverage option with registration	Lennox warranty FAQ
Carrier	Comfort 16 (26SCA5): 10-year parts-only warranty, or 5-year parts plus 3-year labor, with registration within 90 days; 5 years if not registered	Carrier Comfort 16 product page

Is a mini-split better than central air?

A ductless mini-split fits a San Diego home without usable ducts, such as an older house, an addition or an ADU, and central air fits a San Diego home with existing ducts. The table compares the 4 factors that differ.

Factor	Central air	Ductless mini-split
Ductwork needed	Yes	No
Zoning	One system serves the ducted rooms	Indoor units can be turned off or left out of rooms that are not in use
Energy lost in ducts	Ductwork can account for more than 30% of the energy a home uses for space conditioning, according to ENERGY STAR	No duct losses
Best for	Homes with existing ducts	ADUs, additions and homes without ducts

Is a heat pump better than central air with a furnace?

A heat pump heats and cools with 1 system. Heat pumps run in reverse to heat a home in winter, and an ENERGY STAR certified air-source heat pump provides heating for approximately 1/3 the cost of traditional electric heating.

Factor	Central AC and furnace	Heat pump
Equipment	Central AC unit plus a furnace, 2 systems	1 heat pump system
Heating method	The furnace produces the heat	The heat pump moves heat from the outdoor air into the home
Cooling method	Central AC unit	The heat pump runs in reverse to cool

What size replacement AC does a home need?

Tonnage is calculated from the home size, the insulation and the sun exposure; the calculator What Size AC Does a Home Need? estimates the size.

Schedule San Diego AC Replacement Service Today

No matter the HVAC issue, Sandiego HVAC Services has the solution for San Diego residents. Call +1 (858) 392-9754 or send the service request form with name, phone, ZIP or neighborhood and system type. See also AC Installation and Replacement in San Diego, Ductless Mini-Split Installation in San Diego, Heat Pump Installation in San Diego and How Much Does HVAC Cost in San Diego?