Sources

Last checked October 2, 2026. Where a figure is our own assumption, the calculator says so next to the input.

Read directly on the official site

• Mass. Dept. of Energy Resources (DOER), Home Heating Fuels Prices
  Read directly on mass.gov, October 2, 2026. Survey dated 09/28/26.
• U.S. EIA, Electric Power Monthly, Table 5.6.A (average residential price by state)
  Read directly on eia.gov, October 2, 2026. Massachusetts residential, July 2026.
• Mass.gov, Residential electric seasonal heat pump rates
  Read directly on mass.gov, October 2, 2026. Rates effective November 1, 2025.
• U.S. EIA, British thermal units (Btu) conversions
  Read directly on eia.gov, October 2, 2026. Heating oil 138,500 Btu/gal; 1 kWh = 3,412 Btu.
• Mass.gov, Massachusetts municipally-owned electric companies
  Read directly on mass.gov, October 2, 2026.
• MassDOT, Utility Contacts by District/Municipality (electric company per town)
  Read directly, October 2, 2026. Electric company listed for each town.
• Reading Municipal Light Department (RMLD), Residential Rebates
  Read directly on rmld.com, October 2, 2026. The page footer says amounts were last updated December 20, 2024, so confirm with RMLD.
• Middleton Electric Light Department, Incentives & Rebates
  Read directly on middletonlight.org, October 2, 2026.

Mass Save: read from dated Internet Archive copies

masssave.com blocks automated readers, so we could not open the live pages. We read the archived copies of the official pages below. Mass Save amounts are set per year and can change.

• Mass Save, Air Source Heat Pumps (2026 rebates and eligibility)
  masssave.com blocks automated readers, so we read the Internet Archive copy of this exact page saved July 16, 2026. Check the live page for current amounts.
• Mass Save, 0% Interest Financing (HEAT Loan)
  Internet Archive copy of this page saved June 15, 2026. Check the live page.
• Mass Save, Home Energy Assessments
  Internet Archive copy saved July 3, 2026. Check the live page.
• Mass Save, Designated Equity Communities
  Internet Archive copy saved June 14, 2026. The list of communities loads dynamically from your ZIP code, so we could not read it; confirm there.

Census data

• U.S. Census Bureau, American Community Survey 5-year 2020-2024, tables B25040 (house heating fuel), B25034 (year built), B25024 (units in structure)
  The Census API needs a key, so we pulled the same published ACS 2024 5-year tables through Census Reporter (censusreporter.org), which republishes them unchanged.

Our own assumptions (editable in the calculator)

• Gallons from home size: about 0.5, 0.4 or 0.3 gallons per sq ft per year for homes built before 1960, 1960 to 1999, and 2000 or later. A rule of thumb, not an official figure.
• Oil system efficiency 80 percent and heat pump seasonal COP 2.5.
• Heat pump size of about 1 ton per 500 sq ft, and the rule that rebate tons equal AHRI cooling capacity divided by 12,000 Btu.
• Winter rate discounts computed from the Mass.gov rate table: National Grid 6.677 minus 2.440 = 4.24 cents; Eversource (6.264 minus 2.052) plus (4.545 minus 1.492) = 7.27 cents; Unitil 10.176 minus 3.633 = 6.54 cents per kWh.

Not verified

• Current 2027 Mass Save amounts: not announced as far as we know.
• Which communities are Designated Equity Communities (loads dynamically on masssave.com).
• Costs of panel upgrades and oil tank removal: no sourced figure.
• RMLD amounts: the RMLD page says it was last updated December 20, 2024; other sources suggest 2026 changes. Confirm with RMLD.