Which "furnace" do you have?
Look at the outdoor equipment. A single large cabinet on the roof is a packaged unit; a box on a side-yard slab plus an indoor closet unit is a split system. Then the heat source:
- Heat pump
- The most common heating in Phoenix homes built since the 1990s — Gilbert, Chandler, Surprise, Goodyear. The AC runs in reverse; electric strips back it up. Cool air for a few minutes in heat mode is a defrost cycle and normal. Stuck in one mode, or a bill that tripled, is not.
- Rooftop gas/electric package
- Central Phoenix, Tempe, Glendale and older Mesa ranch homes. Gas burner section and AC in one rooftop cabinet, serviced from a ladder. Fails like a gas furnace, but the flue, ignitor and board bake at 150°F all summer.
- Split gas furnace
- Closet or garage furnace with a separate outdoor AC, on Southwest Gas. Fewer of them than in the other metros, but the same fault list — ignitor, flame sensor, inducer, board.
No heat in Phoenix, by system
- Heat pump blowing cool air, constantly. Not defrost if it lasts more than ten minutes. Low charge, a failed outdoor fan, a reversing valve stuck in cool, or a defrost board fault. If the strips have taken over silently you will not notice until the bill arrives.
- Heat pump runs, house never gets warm on a 35°F morning. Capacity falls with outdoor temperature and Valley frost nights are exactly where a marginal unit runs out. Long run times are correct; short cycling and ice that never clears are faults.
- Rooftop unit: inducer runs, click, no flame. Hot surface ignitor cracked from a summer of thermal cycling, or the flame sensor. On a rooftop the tech carries both up the ladder on the first visit.
- Rooftop unit: short cycling. Limit switch tripping on airflow — the same packed filter that hurt the AC in August, or a blower that is failing after the summer.
- Gas furnace: lights, dies in seconds, repeats, locks out. Flame sensor. The furnace sat nine months.
- Any system: burning smell on first start. Dust burn-off for twenty minutes is normal after nine idle months. Persistent, plastic or electrical is not — shut it off.
A short heating season, hard on equipment
Phoenix averages about 1,200 heating degree days a year (NOAA normals; climate zone 2B) — nearly the same as the humid Gulf metros, but concentrated in December and January nights that drop into the 30s while afternoons reach the 60s. Heating equipment here runs a few hundred hours a year, and the calls come in on the first frost warning and the first sustained cold snap, usually the week before Christmas.
What makes Phoenix hard on heating equipment is the summer. A rooftop unit's ignitor, control board and gas valve sit at 150°F in a closed steel cabinet for four months; a heat pump's reversing valve has cycled thousands of times in cooling. The first heating call of the year is when the summer damage shows.
Where in the Valley
Coverage is the City of Phoenix and the ring of Maricopa County cities: Mesa, Chandler and Gilbert in the East Valley; Tempe and Scottsdale; Glendale, Peoria, Surprise, Goodyear and Avondale in the West Valley. Ahwatukee, Arcadia, Paradise Valley and the north Phoenix corridor along I-17 are all in coverage.
The system type tracks the neighborhood age. 1960s–80s ranch homes in central Phoenix, Tempe and older Glendale and Mesa are rooftop packaged units, many of them gas/electric. The stucco subdivisions built since the mid-1990s in Gilbert, Chandler, Surprise, Goodyear and Avondale are split heat pumps. Historic districts — Willo, Coronado, Encanto — have a mix that includes wall furnaces and add-on systems. We ask the year of the house because it usually answers the question.
Permits and licensing in Phoenix
Repairs need no permit. The City of Phoenix Planning and Development Department exempts a like-for-like replacement of cooling equipment that does not increase capacity or move the unit; any new gas piping, a vent rerouted, or a change of fuel or capacity brings the job under permit and inspection. The department's work-exempt-from-permit list is the authority, on the Phoenix Planning and Development site. Mesa, Chandler, Scottsdale, Gilbert and Glendale each run their own building department.
All HVAC contractors in Arizona are licensed by the Arizona Registrar of Contractors. Gas-fired equipment is the one place we would not compromise on that: a licensed tech with a combustion analyzer, not a handyman with a lighter.
Utility programs that touch heating
None of them pays for a repair. Two matter when the repair becomes a replacement decision, and one is a thermostat credit.
| Utility | Program | Relevance to heating |
|---|---|---|
| SRP | Cool Cash rebate — per-ton on a new heat pump, central AC or mini-split at 15.2 SEER2 or better, up to $1,125, through a participating contractor | A heat pump replaces both the furnace and the AC; the rebate applies to the whole unit |
| SRP | Bring Your Own Thermostat — up to $100 in credits plus $25 a year | Smart thermostat, any system |
| APS | Cool Rewards — up to $85 in the first year for enrolling a smart thermostat | Same |
| Southwest Gas | Arizona residential rebates and promotions on qualifying natural gas equipment, searched by address on its site | Gas furnace replacements; check the current list before assuming a furnace qualifies |
SRP residential rebates · Southwest Gas. The federal 25C credit ended for equipment placed in service after 2025.
Phoenix heating repair costs
Mid-range labor; rooftop access adds time. Typical ranges, diagnostic usually credited.
- Diagnostic, ground or rooftop$85–$150
- Flame sensor clean or replace$90–$240
- Hot surface ignitor$150–$350
- Heat pump defrost board or sensor$260–$620
- Reversing valve$550–$1,250
- Limit or rollout switch$150–$320
- Inducer motor$400–$900
- Blower motor$420–$1,200
- Control board$400–$1,000
- Gas valve$300–$700
- Electric heat strip kit$300–$700
Gas smell or a CO alarm
Leave first, call second: Southwest Gas runs a 24-hour emergency line and 911 works. Rooftop units vent above the roofline, but a cracked exchanger still puts combustion gas into the supply air. A CO alarm means everyone out, and the burner stays off until it is tested.
Nine idle months is the reason most of these calls happen. What a Phoenix heating-mode check in October covers, for a heat pump and for a rooftop gas unit. The urgency-ranked fault list for any metro is on the furnace repair page. Frost and freeze warnings: National Weather Service Phoenix.