Comparison
Furnace vs air handler
Both are the indoor box with a blower. Only one makes its own heat from fuel.
Written by HYRE HVAC Research Desk Primary-source research, data analysis and fact checking
The short answer
A furnace makes heat; an air handler mostly moves air. A furnace burns gas, propane or oil, or uses large electric elements, and has a blower to push that heat through ducts.
An air handler is a cabinet with a blower and an indoor coil, paired with a heat pump or AC outdoors. It may hold electric resistance strips for backup heat. Which one you need depends on the outdoor equipment and your fuel.
What is inside each one?
A gas furnace has burners, an ignitor, a flame sensor, a heat exchanger, a draft inducer, a vent connection and a blower. If you have central AC, the indoor coil usually sits in a separate box on top of the furnace, using the furnace blower.
An air handler has a blower, the indoor coil built in, a filter rack, a drain pan, and often a heat strip kit. It has no burner and no flue. It is the standard partner for a heat pump in an all-electric home, and for an AC in homes heated some other way.
Furnace vs air handler at a glance
| Furnace | Air handler | |
|---|---|---|
| Makes heat by | Burning fuel (or electric elements in an electric furnace) | None, or electric strips as backup |
| Pairs with | AC or heat pump (dual fuel) | Heat pump or AC |
| Indoor coil | Separate cased coil on top | Built in |
| Venting | Required for fuel-burning models | None |
| Carbon monoxide | Possible with fuel; needs CO alarms | Not from the unit |
| Rated by | AFUE (heat), matched coil in AHRI for cooling | Part of the heat pump or AC system rating |
Which one does my system need?
If you heat with gas and want to keep it, you need a furnace, and the AC or heat pump coil sits on top.
If you are all-electric with a heat pump, you need an air handler.
If you are going dual fuel, the furnace acts as the air handler for the heat pump and also provides backup heat.
The air handler or furnace blower must deliver the airflow the outdoor unit was rated with. That is why the AHRI Directory lists matched combinations, and why swapping one half of a system without checking the match is a common source of poor performance.
What drives the cost?
For a furnace, the efficiency tier, venting, gas line and the coil on top. For an air handler, the blower type (fixed or variable speed), the size of the heat strip kit and the electrical circuit it needs.
Electric strips need a large circuit, which may raise a panel question. We publish no prices here: we do not yet hold enough sourced, dated quotes to state one honestly. Use the cost hub and the HVAC cost calculator with your own quotes.
Things to check
Both units have a drain from the coil. A blocked drain is a common leak source. Ask whether a float switch is fitted.
Oversized strips run up bills; undersized ones leave you cold during defrost or a heat pump failure.
Ask for the AHRI certificate number for the outdoor unit plus this indoor unit.
Furnace gas connections, venting and combustion checks are licensed work.
Where each one wins
A furnace wins when
You have cheap gas and cold winters.
You want backup heat that does not depend on electricity prices.
You plan a dual-fuel system.
An air handler wins when
The house is all-electric or you want no combustion inside.
The outdoor unit is a heat pump that covers most of your heat.
You want a single cabinet with the coil built in.
Can I switch from one to the other?
Yes, and it is common when moving from a gas furnace and AC to an all-electric heat pump. The ducts usually stay.
The gas line is capped, the vent is removed or sealed, and an air handler takes the furnace’s place. The electrical panel must supply the air handler and its strips.
Going the other way, from an air handler to a furnace, needs gas piping and a vent.
Questions
Is an air handler the same as a furnace?
Does a heat pump need a furnace?
Does an air handler need a vent?
Can I keep my furnace when adding a heat pump?
Where is the air handler usually installed?
Written and audited by
HYRE HVAC Research Desk
Primary-source research, data analysis and fact checking
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