Lexington asks more of a heat pump than Boston does. Clement Boston Heat Pumps handles heat pump installation in Lexington, MA, where the winter nights run colder, more homes burn oil and propane, and a town bylaw keeps new fossil-fuel equipment out of new homes and major renovations.
Each of those three facts pushes the same way: the heat pump has to carry the whole house on the coldest night, without help from a furnace.
Colder nights next to Hanscom Field
Lexington sits inland, beside Hanscom Field. That station averages 5.3 nights a year at or below 0°F; Logan averages 0.6. The heat pump has to be sized for the inland number.
What the cold changes
Hanscom also logs about 19 nights a year at or below 10°F, against about seven at Logan, and roughly 8% more heating degree days. A system sized on Boston’s coastal design temperature runs short on those nights and hands the load to electric backup strips.
How we size for it
- Room-by-room Manual J load, at the design temperature for your address, not the coast’s.
- Capacity at 5°F listed on the estimate, from the maker’s cold-climate data, so you can see what the unit delivers on a sub-zero night.
- Backup lockout, set so strips only run when the heat pump truly can’t keep up; see our aux heat guide.
Our sizing guide explains the method, and do heat pumps work in Massachusetts covers cold-climate performance.
When the fossil-fuel-free bylaw applies
Lexington is one of the towns in the state’s fossil-fuel-free demonstration program. Its bylaw took effect June 22, 2024, with an amendment effective January 1, 2025, and it covers new buildings and major renovations.
Renovations and additions
If your project counts as a major renovation, the new heat is electric. A gas or propane furnace kept as backup isn’t available for that work, so dual fuel is off the table and the heat pump is sized to carry every night alone. That makes the cold-climate sizing above more than a preference.
Straight replacements
Replacing an old furnace or boiler in a house you’re not renovating is a different case. We confirm with the permit which one your project is, before the equipment is chosen.
Oil and propane: over a third of homes
About 31% of Lexington homes burn oil and another 6% propane, well above the state’s 22% oil share. Those homes pay the most per unit of heat, and they get the biggest rebate.
Oil and propane homes
Both qualify for Mass Save’s whole-home rebate through Eversource: $2,650 per ton up to $8,500, becoming $2,350 per ton up to $7,500 from January 1, 2027. A propane supplier collects its own tank once the furnace is gone.
The oil tank comes out with the burner; our typical range for an accessible basement tank is $600 to $1,500, plus the fire department’s permit. See oil to heat pump conversion and the heat pump vs oil guide.
Gas homes
Gas heats about 48% of the town. National Grid sells the gas and sponsors Mass Save’s gas side, so a gas home that removes its furnace qualifies for the same whole-home rebate. Eversource’s winter heat pump rate, which lowers distribution and transmission charges from November through April, narrows the running-cost gap.
Colonials, capes and mid-century houses
Close to three-quarters of Lexington homes are detached houses, and only about one in five predates 1940. The layout of the house, more than its age, decides where the ducts go.
Colonials and capes with a furnace
A warm-air furnace already has ducts. We measure static pressure and return size, since a heat pump moves more air at a gentler temperature, and add a second zone in the attic where the bedrooms run hot or cold. See furnace to heat pump conversion.
Mid-century houses
Some of Lexington’s post-war modern houses sit on slabs, with low-pitched roofs and baseboard or radiant heat. With no basement, ducts run through a low attic, a soffit or a small-duct system. The ductwork page covers those routes.
Older houses near the Center
Lexington’s older houses near the Battle Green and along Massachusetts Avenue often heat with radiators. An attic air handler for the bedrooms and a basement unit for the first floor is the usual layout.
Condos and townhouses
About one Lexington home in eight sits in a building of five or more units. A compact air handler in a closet replaces baseboard or an old furnace, and the association decides where the outdoor unit goes; see our condo guide.
Panels in older houses
A heat pump that carries the whole house on a sub-zero night is a big electrical load, and some older Lexington houses still have 100-amp service. We check the panel on the first visit; if the service has to grow, our typical range for an electrical service upgrade is $3,000 to $6,500.
Paperwork, rebates and code in Lexington
Lexington takes permits through an online permit system. The electrical and sheet metal permits cover most jobs, with a building permit when the work is part of a renovation.
| What | The Lexington figure |
|---|---|
| Electric company | Eversource |
| Gas company | National Grid |
| Fossil-fuel-free bylaw | Effective June 22, 2024; amended January 1, 2025 |
| Energy code | Specialized stretch code since January 1, 2024 |
| Heating fuel | Gas 48%, oil 31%, electricity 14%, propane 6% |
| Nights at or below 0°F | About 5 a year at Hanscom, under 1 at Logan |
Fees and local placement rules for the outdoor unit are confirmed per address. The rebate guide lists every Mass Save condition.
What to expect on a Lexington job
The first visit starts with the bylaw question, then measures what the estimate depends on: room-by-room heat loss, the ducts or new routes, the panel, and an outdoor spot above the snow line.
- Written estimate: equipment with its 5°F capacity, duct work, electrical, tank removal, permits, the rebate path and the price.
- Permits through the town’s online system.
- Install: four to seven working days, longer for new ducts or renovation timing.
- Commissioning: nitrogen pressure test, vacuum below 500 microns, charge by weight, measured airflow, and the backup lockout set for an inland winter.
Arlington shares Lexington’s fossil-fuel-free approach, while Bedford is a comparison town where dual fuel is still allowed.