Dual-Fuel Heat Pumps: Keep Your Boiler or Furnace, Add a Heat Pump

Last updated October 29, 2026Reviewed by Waseem Shahzad, Lead Technician

Dual-fuel heat pump systems that keep your existing boiler or furnace as backup, for homes within 15 miles of Deer Park.

A dual-fuel system adds a heat pump to the boiler or furnace you already have. The heat pump carries most of the heating season and handles the cooling, and the existing system takes over on the coldest days. K2 designs and installs these from our Deer Park shop for homes within about 15 miles.

Call (631) 414-7141 Text us Request service

How does a dual-fuel system decide which heat to use?

It switches at a set outdoor temperature, called the balance point or switchover temperature. Above it, the heat pump heats the house; below it, the boiler or furnace takes over. The switchover is set on the thermostat or a dual-fuel control, and it can be adjusted once you see how the house and your bills respond.

Which Long Island homes fit a dual-fuel setup?

Two kinds of houses fit best. Oil-heated Capes and ranches with baseboard heat can add ductless heat pumps and keep the boiler for the coldest days. Ducted homes can add a ducted heat pump to the existing furnace, so the same air handler and ducts carry both. Both keep a working backup through a cold snap.

Why keep the boiler or furnace?

Keeping the existing system makes sense when it still works well:

Backup on the coldest nights. The boiler or furnace covers the hours when the heat pump would have to work hardest.
A smaller heat pump. Because it doesn't have to carry the design-day load alone, the heat pump can often be sized for most of the season rather than the worst night.
Cooling you didn't have. Baseboard homes gain air conditioning from the same ductless heads.
Less fuel burned. The boiler or furnace runs only below the switchover temperature, so it burns less oil or gas over the season.

How do we set up a dual-fuel system?

Look at the house and the current system. We check the boiler or furnace, the ductwork or baseboard layout and the electrical panel.
Load calculation. We size the heat pump to the house, not to the old system.
Pick the layout. Ducted heat pump on the furnace's air handler, or ductless heads for the rooms you use most alongside the boiler.
Controls. We wire the thermostat or dual-fuel control so the two systems never fight, and set a starting switchover temperature.
Start-up and walkthrough. We run both modes, show you where the switchover is set, and tell you what to watch for in the first cold week.

What does a dual-fuel setup cost?

Our records are too thin to quote a dual-fuel figure yet, because most of our heat pump installs are ductless systems recorded on their own. For planning, our Cost Estimator puts a heat pump replacement at $6,000 to $15,000 and a new heat pump install at $12,500 to $20,000. A dual-fuel job often lands lower than a full replacement because the boiler or furnace stays, and every job is quoted in writing after we see the house. See the heat pump cost guide.

Rebates are claimed through a PSEG Long Island participating contractor or directly with PSEG Long Island; confirm current terms at psegliny.com. K2 is not a PSEG participating contractor and does not file rebate applications. Our 2026 heat pump incentive guide covers the rules, including how dual-fuel setups are treated. Financing is available through Rheem KwikComfort, with credit provided by Synchrony Bank, subject to credit approval. See financing for how it works.

Is dual fuel right for your house?

Dual fuel fits best when the boiler or furnace has years left, the house has no gas service or pays for oil, and you want cooling too. If the boiler or furnace is near the end of its life, compare a dual-fuel setup with a full heat pump system or an oil-to-gas conversion. Our oil to heat pump conversion page compares the options for oil-heated homes.

What does adding a heat pump look like on a real job?

Our records don't yet include a dual-fuel job written up as a project. The closest is a Huntington install in May 2026, where our crew replaced two old cooling systems with one Daikin multi-zone heat pump: a ducted air handler in the attic for the second floor and a ductless wall unit for the living room, on one 36,000 BTU outdoor unit. That is the heat pump half of a typical dual-fuel layout.

Tip from Waseem Shahzad, Lead Technician: on that job Waseem replaced the condensate drain pump along with the equipment because he judged the old one unreliable. When a new heat pump air handler goes in an attic, have the drain pump checked at the same time.

Brands We Install and Service

Our technicians work on all major brands. The ones we install most often (see all brands):

Fujitsu
Daikin
Bosch
Mitsubishi Electric

Areas We Serve

We serve homes within about 15 miles of our shop at 60 S 2nd St, Unit V in Deer Park, across western Suffolk and eastern Nassau County. Local pages for the towns we cover:

What Our Customers Say

"Waseem is excellent. He checked my hearing system, diagnosed the problem and fixed the whole system. Now the heat is working excellently. I am high recommending this company to any person’s house. He is very thorough and spent as much as was needed to repair the heat. We are very thankful. He is excellent. Thank you so much to your company."

Tamara Shashiashvili Google review

"This is my second (distinct) job with K2 HVAC and I couldn't be more appreciative of their prompt and quality services. The first job (a replacement of my heating unit) was handled excellently by Shelby and the second (a replacement of my hot water unit) was amazingly handled by Waseem. The backend customer support is fantastic too, as Sadia is ever responsive by text and phone call. All said, I recommend their services wholeheartedly!"

tobi bell Google review

"This was my first time using K2 Cooling & Heating, and I couldn't be happier with the experience. Waseem arrived on the scheduled day right on time and took the time to listen carefully to the issues I was having with my HVAC unit before beginning any work. He quickly diagnosed the problem and explained everything clearly in a way that was easy to understand. His professionalism, knowledge, and attention to detail were outstanding. He fixed the issue efficiently and made sure everything was working properly before he left. It's refreshing to work with someone who genuinely cares about providing excellent customer service. I highly recommend Waseem and K2 Cooling & Heating to anyone looking for honest, reliable, and knowledgeable HVAC service. I will definitely be using them again in the future!"

Shahid Ali Google review

Dual-Fuel Heat Pumps: Frequently Asked Questions

What temperature should a dual-fuel system switch over at?

There is no single right number. It depends on the heat pump, the house and what you pay for electricity versus oil or gas. We set a starting switchover temperature at installation and adjust it once you have seen a few cold weeks and a bill or two.

Can I add a heat pump to my oil boiler?

Yes. In a baseboard home that usually means ductless heat pumps for the main rooms, with the oil boiler kept for the coldest days and, if it makes your hot water, for that too. The two systems run on their own controls or a shared one.

Will a dual-fuel system cool my house?

Yes. The heat pump is also an air conditioner, so the ducted or ductless system that heats in spring and fall cools in summer. For baseboard homes, that is often the main reason to add one.

Do rebates apply to dual-fuel systems?

Book Dual-Fuel Heat Pumps With K2

Call or text (631) 414-7141 any time, or send the form and we will call you back to schedule. You get the cause and the price before any work starts. Financing is available through Rheem KwikComfort, with credit provided by Synchrony Bank, subject to credit approval.

Call (631) 414-7141 Text us Request service