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A contractor quoting a heat pump installation in Maricopa County has to settle the sizing question before anything else, because capacity in heating mode falls as outdoor temperatures drop and the system has little margin if the unit is undersized going in. Homes in Maricopa County, AZ run heat about five months a year, from November through March. The compressor and reversing valve do see heating-mode cycles through those months, but the harder engineering question is whether the unit can meet demand on the coldest nights without leaning entirely on backup resistance heat. That backup decision, and how it is wired and controlled, is what a licensed installer has to get right at the time of installation.
Ductwork sized for an older system is the variable a contractor has to settle before anything else on a heat pump job. Half the homes in Maricopa County, Arizona were built in 1993 or earlier (2020-2024 ACS 5-year). That means a significant portion of the houses here are carrying ducts that were never laid out with a heat pump's airflow requirements in mind. A contractor will open registers, check trunk sizing, and assess static pressure before the equipment conversation goes far. The electrical service gets the same look, because a heat pump's draw has to match what the panel can actually deliver.
What Gets Installed With a New Heat Pump
The outdoor unit is the piece a homeowner sees first, mounted on a concrete pad beside the house, and it holds the compressor and the coil that exchange heat with outside air. Inside the house, the air handler sits in a utility closet, basement, or attic and moves conditioned air through the home's supply registers.
A reversing valve inside the outdoor unit lets the system shift between heating and cooling, and a refrigerant line set runs between the two units through a small penetration in the wall. The thermostat mounts on an interior wall and gives the homeowner direct control over when and how the system runs.
The drawing shows a typical layout, and a licensed contractor determines exactly how each piece is positioned and connected in your specific home.
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835 severe weather events were recorded in Maricopa County, Arizona 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 Maricopa County, Arizona were built in 1993 or earlier (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesMaricopa County, Arizona holds 1,884,334 housing units (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesOwners occupy 65.2% of the occupied homes in Maricopa County, Arizona (2020-2024 ACS 5-year).
U.S. Census Bureau, 2020-2024 American Community Survey 5-Year EstimatesHeat Pump Installation Rules for Maricopa County, Arizona1 codes & standards
Licensing and Legal Requirements in Maricopa County, Arizona
Arizona requires a contractor licence in good standing: it is unlawful to engage in the business of contracting, to bid, or to act or hold yourself out as a contractor without one.
Weather Events in Maricopa County
Outdoor conditions in this region shape how hard heating and cooling equipment has to work over its lifetime. A heat pump sized and installed for the local climate holds up better and runs more efficiently than one that was not.
835 severe weather events, 2015–2024. Source: NOAA National Centers for Environmental Information, Storm Events Database.