Switching from oil to a heat pump is a sequence of decisions more than a single swap. A typical project runs like this: a room-by-room heat load calculation and a look at how the house is heated today, then a design and a price, any air sealing or insulation the house needs, and installation of the heat pump with its electrical work. Last comes the oil side, which means either retiring the boiler or furnace and removing the tank, or keeping the oil system as backup under an automatic control. If your boiler also makes your hot water, a new water heater belongs in the plan too.
Oil is still a big part of the picture west of Boston. Across the 26 towns OniFix serves, Census estimates show roughly one home in five heats with oil, and in some towns far more: 59 percent of homes in Sherborn, 35 percent in Milford and 33 percent in Hopkinton. Here is what each stage of the conversion involves.
The assessment: four things to pin down first
The heat load. A sound design starts with a room-by-room heat load calculation, usually ACCA Manual J, at your area's winter design temperature. The size of the existing oil boiler is not a useful guide, since older boilers are often much larger than the house needs. The room-by-room numbers set how much heat pump capacity you need and, in a ductless design, how large each indoor unit should be and where it goes. Mass Save ties its whole-home rebate to this calculation: the system must be sized to cover 90 to 120 percent of the home's total heating load at design conditions. If you're wondering how that capacity holds up in January, our article on heat pumps in a Massachusetts winter explains what changes as the temperature drops.
How the house is heated now. An oil furnace means there are ducts, and the conversion can often use them. An oil boiler means hot water radiators or baseboard (or, in some older homes, steam), and the heat pump will need its own way to get heat into the rooms.
Electrical capacity. A heat pump adds a large electric load to a house that has been heating with oil. Whether the existing panel and service can carry it should be settled early, because the answer can add cost and time.
Weatherization. Air sealing and insulation reduce the heat load, which can shrink the equipment you need and the hours it runs. For Mass Save's whole-home rebate, the house must be sufficiently weatherized before the heat pump goes in, and a no-cost Mass Save Home Energy Assessment is the usual starting point.
Three ways to convert, depending on your system
Oil furnace homes: a ducted heat pump on the existing ducts
With a forced hot air oil furnace, the most direct path is a ducted heat pump: an outdoor unit paired with an indoor air handler that uses your existing ductwork. The ducts deserve a careful look first. Heat pumps deliver air at a lower temperature than a furnace, so they move more air to carry the same heat, and ducts that were adequate for a furnace can turn out noisy or undersized. Leaky ducts running through an unheated attic or crawlspace waste heat no matter what feeds them. Sealing, resizing a few runs or adding a return is common.
Oil boiler homes: ductless or ducted mini splits
Homes with radiators or baseboard have no ducts, so the heat pump brings its own distribution. Ductless wall-mounted units are the usual choice for main living areas. Compact ducted mini split air handlers, hidden in an attic or closet with short duct runs, can serve a cluster of bedrooms without a unit on every wall. Many homes end up with a mix. The thing to plan around is closed doors: one indoor unit in an open living room can heat a lot of space, but a bedroom with the door shut at night needs heat delivered into it.
Partial conversion: the heat pump leads, oil stays as backup
You don't have to remove the oil system on day one. In a partial conversion, the heat pump carries most of the heating season and the existing boiler or furnace covers the coldest stretches. An integrated control decides which system runs based on the outdoor temperature. Mass Save's partial-home rebate requires an integrated control from its qualified list wherever oil heat stays in use, with the switchover set at 30°F or lower. This route makes sense when the oil equipment is relatively young, when the budget doesn't yet stretch to full capacity, or when the house needs weatherization that will take time. The trade-off is that you keep the tank, the deliveries and the annual burner service, even as you burn less oil.
If your boiler makes your hot water
This is the detail that catches people. Many oil boilers also heat the household's domestic hot water, either through a tankless coil inside the boiler or by feeding an indirect storage tank beside it. If there's no separate water heater in the basement, the boiler is almost certainly doing the job. Remove the boiler and the hot water goes with it.
There are three ways to handle it. A heat pump water heater is the natural partner for a heat pump conversion: it pulls heat from the surrounding air, works best in a basement or utility room with space around it, and currently qualifies for a $750 Mass Save rebate on eligible units. A conventional electric tank is simpler to install but costs more to run. The third option is to keep the boiler for hot water only. Mass Save's whole-home rules allow the old system to stay in place for domestic hot water as long as its space heating is disabled, but that also keeps the oil tank, the deliveries and the burner service. Our page on water heater replacement covers the choices in more detail.
The electrical work
Each outdoor unit typically needs its own 240-volt circuit and a disconnect nearby, and a ducted air handler with backup heat strips can need a large circuit of its own. In homes with older or smaller electrical service, the load calculation sometimes shows the panel or the service itself has to be upgraded, and a service upgrade involves the utility, which affects the schedule. This work is done by a licensed electrician under an electrical permit and inspected by the town. If you qualify for Mass Save's income-based Turnkey Services, an electrical panel upgrade that the heat pump requires may be covered at up to 100 percent.
What happens to the oil tank
Once the oil system is fully retired, the tank has to go. The Massachusetts fire code, 527 CMR 1.00, treats a tank as abandoned once it has gone more than 12 months without being filled or drawn from (for tanks up to 10,000 gallons), and abandoned tanks and their piping must be removed. Leaving an empty tank in the basement just in case isn't a long-term option.
Removal is permitted work. The permit comes from the head of your local fire department, and whoever removes the tank must provide a receipt within 72 hours showing it was delivered to the site named on the permit. For a basement or garage tank, plan the last oil delivery so the tank runs low before the switch rather than topping it off. Buried tanks involve more. Within 24 hours after an underground tank and its piping come out, the owner has to have the site tested for an oil release, and any contamination must be reported to the fire department and MassDEP. Leaving a buried tank in the ground is allowed only in limited cases and only with the fire department's approval.
Paying for it in 2026
Mass Save's 2026 air source heat pump rebates break down like this:
- Whole-home: $2,650 per ton, up to $8,500. The heat pump must be the sole source of heating and cooling, so the oil system has to be removed or disconnected (for example, with the fuel line disconnected and capped). The home must be sufficiently weatherized, and the equipment must be ENERGY STAR Cold Climate and on Mass Save's qualified products list.
- Partial-home: $1,125 per ton, up to $8,500, with an integrated control wherever oil stays in use. A $500 sizing bonus and a $500 weatherization bonus are available to projects that qualify.
- Income-based enhanced: up to $16,000, or a heat pump at up to no cost through Turnkey Services, for qualifying households that heat with oil, propane or electric resistance.
Those amounts apply to equipment installed by December 31, 2026, with the application received by February 28, 2027. For projects installed on or after January 1, 2027, whole-home drops to $2,350 per ton capped at $7,500, and partial-home to $1,000 per ton capped at $7,500. Every one of these rebates requires an installer who participates in the Mass Save Heat Pump Installer Network, so confirm that with any contractor before you sign. Mass Save's HEAT Loan offers 0 percent financing up to $25,000 for qualifying upgrades, heat pumps included; apply before the installation. There is no federal tax credit for a heat pump installed in 2026, because the Section 25C credit ended for equipment placed in service after December 31, 2025.
One local exception: Concord, Hudson and Wellesley get their electricity from municipal light plants, so Mass Save's electric heat pump rebates don't apply to oil-heated homes there. Each light plant runs its own program. For the full rules and paperwork, see our guide to Mass Save heat pump rebates.
Will a heat pump cost less to run than oil?
It depends on four numbers, all specific to your house and your bills: what you pay per gallon of oil, what you pay per kilowatt-hour of electricity (all in, supply plus delivery), how efficient your oil system really is, and how efficiently the heat pump runs across the season, including how often any backup comes on. You can make a rough comparison yourself.
A gallon of ultra-low sulfur heating oil holds about 137,400 BTU. Burned in a boiler at a hypothetical 85 percent efficiency, about 117,000 BTU of that reaches the house. A heat pump averaging a seasonal COP of 2.5 would need roughly 14 kWh of electricity to deliver the same heat, and at a COP of 3 about 11.4 kWh. So compare what you pay for one gallon of oil with the cost of 11 to 14 kWh at your electric rate. If the electricity costs less, the heat pump comes out ahead on heating; if it costs more, it doesn't. An older boiler running below 85 percent tilts the math toward the heat pump, and many hours on electric resistance backup tilt it the other way.
Two more factors belong in the comparison. Eligible customers of Eversource, National Grid and Unitil can get a seasonal heat pump rate, with lower electric rates from November through April; check with your utility whether you qualify. And if you didn't have central air before, the heat pump will add to your summer electric bills whenever you use it to cool. Mass Save's Heating Comparison Calculator is a useful way to run the numbers with current prices.
If you're thinking about moving off oil, our heat pump installation page explains how we look at a home, from the ducts or radiators to the electrical panel, before recommending anything, and you'll have the price before any work starts.
Sources: Mass Save air source heat pump rebates; Mass Save whole-home heat pump verification form; Mass Save enhanced residential offers; Mass Save heat pump water heaters; Mass Save HEAT Loan; Mass Save seasonal heat pump rates; 527 CMR 1.00, Massachusetts Comprehensive Fire Safety Code; Removing your underground heating oil tank (mass.gov); IRS Energy Efficient Home Improvement Credit; EIA energy conversion calculators.