Geothermal vs. a New Furnace or Boiler in New Jersey: How to Decide

How each system makes heat

A furnace or boiler makes heat by burning fuel, usually natural gas, propane or oil. A furnace heats air and pushes it through ducts. A boiler heats water and sends it to radiators or baseboards.

A geothermal system doesn't burn anything. A few feet below the surface the ground stays at a fairly steady temperature all year, cooler than the air in summer and warmer than the air in winter. Pipes buried in the yard, called a ground loop, carry fluid through that steady-temperature ground. A heat pump inside the building moves heat from the loop into the house in winter and from the house back into the ground in summer. It runs on electricity.

That last part is the first big difference: a geothermal system heats and cools. A furnace or boiler only heats, so most homes pair it with a separate air conditioner.

What geothermal does well

• One system for heating and cooling. The same equipment handles both seasons.
• No fossil fuel burned on site. There's no burner, no flue and no fuel delivery, and no combustion happening inside the house.
• Efficient. Moving heat takes less energy than making it, which is why geothermal is known for low operating costs. What you actually save depends on your house, your current fuel and your electric rate, so ask for numbers specific to your property.
• Nothing loud outside. There's no outdoor condenser sitting in the weather the way there is with a conventional air conditioner.
• Steady output in cold weather. Because the loop draws on ground temperature and not on outdoor air, a cold snap doesn't change what the system has to work with.

What a furnace or boiler does well

• Lower cost to install. The equipment is simpler and there's no ground loop to put in.
• Fast replacement. Swapping a like-for-like furnace or boiler is a much smaller job than a geothermal installation. If the heat is already out and it's cold, that matters.
• Fits what the house already has. A new boiler connects to existing radiators and baseboards. A new furnace connects to existing ducts.
• No yard work. Nothing has to be drilled or dug.

What decides it for your property

The right answer usually comes down to a handful of practical questions.

• Is it new construction or an existing home? Geothermal is easiest to plan into a new build, when the loop, the ductwork and the mechanical room can all be designed together. Existing homes can be retrofitted, but there's more to work around.
• Is there room for a ground loop? Loops can run horizontally in trenches, which takes open yard, or vertically in drilled bores, which takes less surface area. Driveways, septic fields, wells, ledge and mature trees all affect what's possible on a given lot.
• How does the house deliver heat now? Homes with ducts are the simplest geothermal retrofits. Homes heated by a boiler with radiators or baseboards, which is common in older houses around Phillipsburg and Washington, may need ductwork added or a different approach. Duct installation and retrofitting can be part of the same job.
• How is the electrical service? A heat pump adds electrical load. An older panel may need to be looked at.
• How long will you own the building? Geothermal costs more up front and pays back over time through lower running costs. The longer you plan to stay, the more that trade works in your favor.
• Is the existing system failing right now? If you have no heat today, a conventional repair or replacement gets you warm fastest. You can still plan a geothermal project for later.

For commercial buildings the same questions apply, along with how the space is used, the hours it runs and how much cooling it needs.

About auxiliary heat

Many geothermal systems include auxiliary heating, a backup heat source that helps on the coldest days or covers the building if the heat pump needs service. It's worth asking how any system you're quoted handles backup heat, and whether your existing equipment could play that role.

About incentives

Tax credits, utility rebates and state programs for geothermal change from year to year, and the rules matter. Don't count on a figure you read online. Check the current federal and New Jersey programs yourself, or ask your tax preparer, before you build an incentive into your budget.

Don't wait on a system that isn't safe

A replacement decision can take a few weeks. A safety problem can't. If you smell gas, don't flip switches or try to find the leak. Leave the building, get everyone out, and call your gas utility or 911 from outside. If a carbon monoxide alarm sounds, get out into fresh air and call 911.

Soot around the furnace or boiler, a burner flame that's yellow when it used to be blue, or a system that keeps shutting itself off are all reasons to turn it off and have it checked before you run it again.

Questions to ask any contractor

• Can my lot take a ground loop, and which type?
• Can my existing ducts or radiators be used, and what would need to change?
• What does the system use for backup heat?
• Will my electrical service handle it?
• What would a conventional replacement cost by comparison, in writing?
• Who services the system after it's installed?

Talk it through with New Ark

New Ark installs geothermal systems in new construction, retrofits existing homes and adds auxiliary heating, and also repairs and replaces furnaces and boilers, for residential and commercial customers. That means you can get both options looked at by one contractor. We work from 412 Firth St in Phillipsburg and serve Warren, Hunterdon, Sussex, Morris and Somerset counties. We're licensed and insured in New Jersey, and you can request a written estimate online.

Call 908-454-4043. Every call is answered, day or night, and no-heat emergencies go first. See geothermal heating and cooling or heating repair and replacement.

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