Boston / Watertown
Watertown has 35,543 residents (give or take 33) (ACS 2020-2024 5-year, table B01003, https://data.census.gov/table/ACSDT5Y2024.B01003?g=060XX00US2501773405, checked 2026-10-19), about 8,895 people per square mile.
Watertown is about 8 miles from the Census center point for Boston in a straight line and covers 3.996 square miles of land (Census 2024 Gazetteer internal points and land area, https://www2.census.gov/geo/docs/maps-data/data/gazetteer/2024_Gazetteer/, checked 2026-10-19).
The quote form takes a ZIP code; for Watertown that is 02472 (Census 2020 ZCTA to county subdivision relationship file, ZIP areas at least 20% inside the town, https://www2.census.gov/geo/docs/maps-data/data/rel2020/zcta520/tab20_zcta520_cousub20_natl.txt, checked 2026-10-19).
Median household income in Watertown is $126,265 (ACS 2020-2024 5-year, table B19013, https://data.census.gov/table/ACSDT5Y2024.B19013?g=060XX00US2501773405, checked 2026-10-19); Mass Save's enhanced heat pump incentives are income-based and decided household by household, so the town median only hints at how many neighbors qualify.
At 8,895 people per square mile, Watertown is dense enough that noise setback rules and outdoor-unit placement on a small lot are the first questions the installer works through.
17% of Watertown homes are single-family detached, 43% are in two- to four-unit buildings and 30% are in buildings of five or more units (ACS 2020-2024 5-year, table B25024, https://data.census.gov/table/ACSDT5Y2024.B25024?g=060XX00US2501773405, checked 2026-10-19).
A two- or three-family building is the common Watertown case at 43% of the stock against 17% detached houses, and each unit usually gets its own small outdoor unit and its own rebate account rather than one big system for the building. With 52% of Watertown homes rented (ACS 2020-2024 5-year, table B25003, https://data.census.gov/table/ACSDT5Y2024.B25003?g=060XX00US2501773405, checked 2026-10-19), the landlord signs the quote in many of them.
Watertown has 29 points fewer detached houses than Middlesex County overall (46%) (ACS 2020-2024 5-year, table B25024, https://data.census.gov/table/ACSDT5Y2024.B25024?g=050XX00US25017, checked 2026-10-19).
52% of Watertown homes are rented (ACS 2020-2024 5-year, table B25003, https://data.census.gov/table/ACSDT5Y2024.B25003?g=060XX00US2501773405, checked 2026-10-19), so the market splits between resident-led jobs where the occupant picks the system and landlord-led jobs where they do not, and the rebate paperwork differs.
Of the 16,371 occupied homes in Watertown, 67% heat with natural gas, 13% with heating oil, 15% with electricity and 4% with propane (ACS 2020-2024 5-year, table B25040, https://data.census.gov/table/ACSDT5Y2024.B25040?g=060XX00US2501773405, checked 2026-10-19).
Gas leads in Watertown at 67%, but 16% of homes still burn delivered oil or propane, and those 2,619 or so homes are where a heat pump pays back fastest.
Watertown has 5 points less oil heat than Middlesex County as a whole, where 18% of homes burn oil, and 3 points less electric heat than the county's 18% (ACS 2020-2024 5-year, table B25040, https://data.census.gov/table/ACSDT5Y2024.B25040?g=050XX00US25017, checked 2026-10-19).
Eversource Energy lists Watertown among the Massachusetts communities it serves for electricity (Eversource Energy communities we serve, https://www.eversource.com/residential/services/communities-we-serve, checked 2026-10-19).
For a Watertown address billed by Eversource Energy, the Mass Save whole-home heat pump rebate is $2,650 per ton up to $8,500, and the partial-home rebate is $1,125 per ton up to $8,500; for projects installed on or after January 1, 2027, the whole-home figure drops to $2,350 per ton capped at $7,500 (Mass Save air-source heat pump rebates, https://www.masssave.com/residential/rebates-offers-services/heating-and-cooling/heat-pumps/air-source-heat-pumps, checked 2026-10-19).
Watertown has 17,206 housing units, 44% built before 1940 and 78% before 1980, with 13% built in 2000 or later (ACS 2020-2024 5-year, table B25034, https://data.census.gov/table/ACSDT5Y2024.B25034?g=060XX00US2501773405, checked 2026-10-19).
Watertown has 12 points more pre-1940 homes than Middlesex County as a whole (32%) (ACS 2020-2024 5-year, table B25034, https://data.census.gov/table/ACSDT5Y2024.B25034?g=050XX00US25017, checked 2026-10-19). An older stock means more insulation upgrades before the heat pump goes in.
The median Watertown home was built in 1947 (ACS 2020-2024 5-year, table B25035, https://data.census.gov/table/ACSDT5Y2024.B25035?g=060XX00US2501773405, checked 2026-10-19) and the median home has 5.1 rooms (ACS 2020-2024 5-year, table B25018, https://data.census.gov/table/ACSDT5Y2024.B25018?g=060XX00US2501773405, checked 2026-10-19).
With 44% of homes built before 1940 and only 13% new enough to pass on age, the first question for a Watertown house is insulation: the whole-home rebate wants proof the house is weatherized, and a no-cost home energy assessment is the usual way an older home shows it.
Heating design temperature: 1F. Source: ENERGY STAR Design Temperature Limit Reference Guide (2019 Edition), Middlesex County row, 99% heating, PDF page 56 of 141 (Revised 11/11/2020), https://www.energystar.gov/sites/default/files/Design%20Temperature%20Limit%20Reference%20Guide%20(2019%20Ed)%20-%20ENERGY%20STAR%20Single-Family%20New%20Homes_Rev11.pdf, fetched 2026-10-19, 99%.
That 1F figure is the Middlesex County cold-day number a Watertown heat pump is sized against, so ask the installer to show the system's heating output at 1F, not at the milder rating-label temperature.
Ask whether the quote is whole-home or partial-home, because with 67% of Watertown on gas and 15% already electric the two paths carry different rebate figures and different sizing.
Ask for the heat-loss calculation room by room; a Watertown house from before 1940 (44% of the 17,206 units) rarely matches a square-footage rule of thumb.
The form on this page is the follow-up for Watertown. The public number is the number the contractor quotes from.
No local contractor is named on this door for Watertown yet. A request from this page goes to the first licensed shop that takes the door.