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Guide Updated October 8, 2026

Geothermal Heat Pump vs. Gas Furnace: How to Choose

How a geothermal heat pump and a gas furnace differ: how each works, what each needs, what changes the cost, and the questions to ask before choosing.

Key points

  • The property, the years you will own it, cooling needs and local prices decide it.
  • Geothermal needs ground and a larger first cost; a furnace is simpler to replace.
  • We assess the property and compare like with like before recommending either.

A gas furnace burns fuel to make heat. A geothermal heat pump does not burn anything: it moves heat between the ground and the house, and it runs the same equipment backwards to cool in summer. The two are not rivals so much as different answers to different properties.

This guide compares how each one works, what each one needs, what changes the cost, and the questions worth asking before you choose.

Property cutaway comparing a geothermal ground loop and indoor heat pump with a gas forced-air furnace
What to notice: Geothermal needs suitable ground-loop space and moves heat through buried piping. A gas furnace burns fuel and distributes heat through ductwork. Conceptual illustration; exact equipment and layout vary.

How each system works

The gas furnace

Gas or propane burns in the furnace. A metal part called the heat exchanger holds the flame’s heat, the exhaust leaves through a vent, and a blower pushes the warm air through the ducts. A separate air conditioner handles the cooling season, usually sharing the same ducts and blower.

A gas furnace needs a suitable fuel supply, combustion venting and regular professional maintenance. Its capacity must match the building’s heating needs.

The geothermal heat pump

In a common closed-loop design, buried piping circulates a heat-transfer fluid between the ground and an indoor heat pump. The system moves heat into the house in winter and into the ground during cooling. Open-loop and other designs work differently; the installer should explain which design suits the property.

It needs electricity, a suitable area of ground for the buried loop, and a specialist contractor to design the loop for the property.

What each one needs from your property

Gas furnace Geothermal heat pump
Fuel Natural gas or propane Electricity to run the unit
Cooling A separate air conditioner, or a paired heat pump Included, from the same unit
Space A small footprint indoors, plus a vent Indoor unit plus ground area for the loop
Installation Straightforward, especially a like-for-like replacement Larger project: loop trenches or drilled boreholes
Maintenance Yearly safety and tune-up Yearly check of the unit, the loop pressure and the pump

Incentives change often. If a tax credit or utility rebate applies to the system you are considering, we will point you to the current program rather than quoting yesterday’s terms, and you can confirm eligibility with the program itself.

Running cost: what is fair to expect

A geothermal unit delivers several units of heat for each unit of electricity it uses, so it usually runs for less than electric resistance heat and competes well with gas in many properties. How it compares on your bill depends on your local gas and electricity prices, the house’s insulation, and how cold the winters are. The only way to get your number is to compare quotes against your actual usage.

A furnace’s running cost follows the gas price and the furnace’s efficiency rating. That comparison is one we can show side by side in writing for your own building.

Design for the local winter

Either system needs a design that meets the building’s winter heating load. For geothermal, ground conditions, loop size and fluid temperatures affect performance. Ask the designer how the proposed equipment will meet cold-weather demand and whether backup heat is included.

A note on safeties

A furnace burns fuel, so it needs a yearly inspection of the heat exchanger and a working carbon monoxide alarm near the bedrooms. A geothermal unit has no flame, but it holds refrigerant and water under pressure, and any work on those parts belongs to a trained technician.

How we help you decide

We look at the property, its loads, its ducts, the ground available and the local utility prices. Then we explain both paths in writing, with the work each one involves and what changes the cost of each. The quote lists parts and labor separately.

Sources

Need help with this?

Geothermal

Our geothermal page describes the work and how to book it. We assess the system, explain what we found and provide a written quote for approval before work begins.

Before you call

Safe checks, and what needs a professional

Leave these to a professional

  • Smoke, flames or signs of a fire: leave the building, stay out and call 911.
  • A gas smell: leave the building and call your gas provider first, then call us.
  • Water leaking around the equipment, or staining near a ceiling unit.
  • Ice on the coils, or an outdoor unit that runs without cooling.
  • A breaker that trips repeatedly whenever the system starts.

Safe checks you can do yourself

  • Check the thermostat: is it set to heat or cool, and is the set point where you expect?
  • Check the filter: a clogged filter limits airflow. Replace it if it is visibly dirty.
  • Check the power: look at the breaker and the equipment switch near the unit.
  • Check the airflow: hold a hand at a supply register and feel whether air is moving.
  • Check the outdoor unit: clear leaves and debris from around it.

What changes the cost

We do not publish prices because both systems vary property to property. The honest factors for each

  • Furnace.

    the size the house needs, the efficiency level, the condition of the existing ductwork, and any vent or chimney changes.

  • Geothermal.

    the loop type (trenches versus drilled boreholes), soil and rock, access for machinery, the size of the house, and whether the ductwork can be reused.

The four questions that decide it

  • What does the property allow?

    Geothermal needs ground. A flat, open yard with space for trenches or a drilling rig is very different from a small urban lot or ledge rock.

  • How long will you own it?

    Compare the installed cost and estimated running costs over the years you expect to own the property. Savings and payback are not guaranteed.

  • Do you need cooling too?

    A geothermal unit includes it. With a furnace, cooling is a second system and a second purchase.

  • What are the local prices?

    Cheap gas against expensive electricity, or the reverse, changes the answer completely.

Common questions about Geothermal Heat Pump vs. Gas Furnace

Does a gas furnace need electricity?
Yes. Even a gas furnace needs electricity for the blower and the controls, so a power cut stops the heat even though the burner burns fuel.
What should I know before asking for a quote?
The age of the current equipment, the size of the yard and the space for the indoor unit all shape the answer. We look at the rest with you.
Who can install or service the system I choose?
See geothermal for ground-source systems, or heat pump service for air-source ones.

Heating and cooling service · Hillside IL

Heating and cooling service in Hillside IL

SquareHVAC repairs, replaces and maintains heating and cooling systems for homes and businesses in Hillside IL and the surrounding communities.

We inspect the equipment, explain what we find and provide a written quote with parts and labor listed separately. You decide if and when the work happens. Serving homeowners and businesses since 2009.

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