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Sizing and installation quality are not abstract concerns here: they are what the compressor pays for over years. Homes in Los Angeles County, CA run cooling about four months a year, from June through September. A compressor cycling through that kind of sustained demand wears at the contactor, the capacitor, and the refrigerant connections in proportion to how hard it was ever asked to work. A system that was undersized at installation, or whose refrigerant charge was set carelessly, runs longer per cycle and reaches those failure points sooner. A contractor quoting a new system in this county has to do a proper load calculation before specifying equipment, because the install decision compounds across every season the homeowner owns the unit.
Existing ductwork is what decides how a central AC installation goes here, and most of the time it is what a contractor has to open and measure before anything else on the job moves forward. Half the homes in Los Angeles County, California were built in 1965 or earlier (2020-2024 ACS 5-year). Ductwork laid down for older equipment was sized and routed for a different load, and a new central system has to move air through whatever those runs allow. If the ducts cannot carry it, the installation scope changes before the unit is ever chosen. Electrical service gets checked for the same reason.
What Gets Installed With a New Central AC
The outdoor condenser unit sits on a concrete pad beside the house and holds the compressor and condenser coil, the two components doing the heaviest work in the system. Inside, the air handler mounts in a utility closet, attic, or garage and moves conditioned air through the home.
The evaporator coil attaches directly to the air handler and is where the air gives up its heat before the blower pushes it through the ducts. A copper refrigerant line set runs between the indoor and outdoor units, and a programmable thermostat mounts on an interior wall to control the whole system.
The drawing shows a typical layout, and a licensed contractor determines exactly what goes where in your home.
Get matched in Los Angeles CountyLos Angeles County, by the numbers
136 severe weather events were recorded in Los Angeles County, California between 2015 and 2024.
NOAA National Centers for Environmental Information, Storm Events Database, bulk CSV export, events 2015-01-01 through 2024-12-31.Half the homes in Los Angeles County, California were built in 1965 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesLos Angeles County, California holds 3,650,466 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 45.9% of the occupied homes in Los Angeles County, California (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesRules & Standards Governing Central AC Installation in Los Angeles County, California9 sourced rules and standards
What the installation actually looks like
Split-system central air conditioners rated below 45,000 Btu/h manufactured on or after January 1, 2023 must meet a federal minimum of 13.4 SEER2.
Split-system central air conditioners rated at or above 45,000 Btu/h manufactured on or after January 1, 2023 must meet a federal minimum of 13.4 SEER2.
Split-system central air conditioners manufactured between January 1, 2015 and December 31, 2022 had to meet 13 SEER, the metric that preceded SEER2.
Single-package central air conditioners manufactured on or after January 1, 2023 must meet a federal minimum of 13.4 SEER2.
Space-constrained central air conditioners manufactured on or after January 1, 2023 must meet a federal minimum of 11.7 SEER2.
Federal efficiency standards for split-system central air conditioners and heat pumps are set on each certified combination of outdoor unit and indoor coil rather than on the outdoor unit alone.
Residential and light commercial air conditioning and heat pump systems assembled in the field, including mini-splits and unitary systems, may not be installed on or after January 1, 2025 using a refrigerant with a global warming potential above 700.
A field-assembled system whose specified components were all manufactured or imported before January 1, 2025 carries no installation compliance date under the refrigerant restrictions and may still be installed.
Licensing and Legal Requirements in Los Angeles County, California
California requires a state contractor license: it is a misdemeanour to engage in the business of, or act in the capacity of, a contractor in California without one, unless the work is exempt.
Weather Events in Los Angeles County
Outdoor conditions in Los Angeles County set the workload that a central AC system has to handle year after year. That workload shapes what equipment makes sense here and how hard it will run.
136 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.