Switching to a Heat Pump with Your Existing Ductwork: Cost and When It Works (Phoenix 2026)

A lot of Valley homes, especially older ones and some in Chandler, Mesa and central Phoenix, still have a straight AC with a gas furnace. When the AC is due for replacement, the question comes up: can a heat pump go in on the ducts we already have, and what does it cost?

Short answer: in the Valley, usually yes, and it costs about the same as replacing the AC and furnace like for like.

These are market ranges, not our price list. Our number is a written quote after we've seen the house.

Why Phoenix ducts usually work for a heat pump

Ducts are sized for airflow, and cooling needs more airflow than heating. In a cold climate, the heating load can be bigger than the cooling load, so switching to a heat pump sometimes means bigger ducts. In Phoenix it's the opposite. Your ducts were sized for July. A heat pump of the same tonnage moves the same air, so the existing ductwork is almost always the right size.

What matters more is condition. Ducts in a 150° attic that leak 20 to 30% waste the upgrade no matter what equipment is on them.

What changes in the swap

• Outdoor unit. The AC condenser is replaced with a heat pump of the same size (sized by load calculation, not the old label).
• Indoor unit. The gas furnace comes out and an air handler with electric heat strips goes in, in the same closet, garage or attic spot.
• Electrical. Heat strips need their own 240-volt circuit and breaker. That's the main new cost.
• Gas. The furnace gas line is capped and tested. If the water heater, stove or fireplace still uses gas, the gas service stays.
• Venting. The furnace flue is removed or capped at the roof.
• Thermostat. Must be a heat pump thermostat with the reversing valve wired correctly.

Ducts, returns, registers and usually the line set route stay where they are.

What it costs

Most AC-plus-gas-furnace to heat pump swaps in the Valley land inside our normal heat pump replacement ranges, plus the conversion items:

Typical all-in for a 3.5 to 4 ton conversion with no panel or duct work: about $8,000 to $14,500 installed. Two-stage and variable-speed systems cost more.

Compare that to replacing an AC and gas furnace like for like, which runs about the same or more because you're buying two appliances. The heat pump replaces both.

Is the heat pump cheaper to run?

For most Valley homes, yes. Heating here is short and mild, and a heat pump delivers roughly two to three units of heat for every unit of electricity in those conditions. You also drop the furnace's annual safety check, the carbon monoxide risk, and in many homes the minimum gas bill if nothing else uses gas.

One thing to expect: heat pump air comes out of the vents at roughly 90 to 100°F, not the 120 to 130°F a gas furnace blows. The house gets just as warm, but the air at the register feels cooler. Most people stop noticing after a week.

When to keep the furnace

• The furnace is under 10 years old and working. Keep it. Pair it with a heat pump and a matched coil (called dual fuel), or just replace the AC.
• You like gas heat. Plenty of people do. It's a comfort choice, not a wrong one.
• The panel can't take another big circuit and an upgrade isn't in the budget.

A good contractor quotes both options side by side.

Converting from oil or electric baseboard

Oil heat is rare in Arizona. Most homes searching "convert oil to electric heat" here have a very old system or a property built elsewhere. Same logic applies: if there's ductwork, a ducted heat pump goes in on it. If there isn't, a ductless mini split is usually the better path.

Rebates

SRP Cool Cash covers heat pumps at 15.2+ SEER2: $75 per ton single-stage, $150 two-stage, $225 variable-speed, through April 30, 2027. APS ended its equipment rebate in 2026, and the federal 25C credit expired at the end of 2025. Rebate details.