Massachusetts · NOAA station KBOS
Heating with a mini-split in Boston, MA
The short answer
In Boston, a median ENERGY STAR cold-climate mini-split heating a 24,000 BTU/h design load should cost about $2,018 a year: $605 more than natural gas (90% efficient), and 62% less than electric resistance. The 99% design temperature is 14°F, so capacity at 5°F rarely decides anything here.
The winter you are actually buying for
This is Boston's average year of hourly temperatures from 2015 through 2024 (87,656 readings at Gen E L Logan International Airport, 100% of all hours). The dashed line is the 99% design temperature: only 1% of hours are colder.
What it costs, by fuel
Mini-split modeled as a median certified cold-climate unit sized to cover the load at 14°F. Seasonal efficiency in Boston's weather: COP 2.64. In 92 hours a year the load exceeds capacity and the estimate adds electric backup.
Three house sizes
| Design load | Heat pump | Gas | Oil | Propane | Resistance | Seasonal COP | Systems that cover it |
|---|---|---|---|---|---|---|---|
| 12,000 BTU/h | $1,009 | $707 | $774 | $1,386 | $2,663 | 2.64 | 10,969 of 14,941 |
| 24,000 BTU/h | $2,018 | $1,413 | $1,547 | $2,772 | $5,326 | 2.64 | 5,548 of 14,941 |
| 36,000 BTU/h | $3,027 | $2,120 | $2,321 | $4,158 | $7,989 | 2.64 | 2,802 of 14,941 |
The last column counts ENERGY STAR cold-climate systems whose published 5°F and 47°F capacities, joined by a straight line, still reach the design load at Boston's 14°F. How sizing works.
Not a quote. Real bills depend on insulation, thermostat habits, installation and your own Manual J. Use this to decide whether a heat pump is worth pricing, then get two local quotes.
Questions people ask
Will a mini-split work in Boston in winter?
Yes, if it is a cold-climate model. Boston's 99% design temperature from 2015–2024 hourly data is 14°F, and the lowest hour recorded was -9°F. The median ENERGY STAR cold-climate unit keeps 88% of its 47°F heating capacity at 5°F. Hours per year at or below 5°F in Boston: 10.
Is a heat pump cheaper than natural gas in Boston?
At a 24,000 BTU/h design load, we estimate $2,018 a year with a median cold-climate mini-split versus $1,413 for natural gas at 90% efficiency, using 30.39¢/kWh electricity and 2024 Massachusetts fuel prices. That is $605 more than natural gas.
How big a mini-split do I need in Boston?
Size to your home's heat loss at 14°F, not to square feet. For a 24,000 BTU/h load, a unit shaped like the median certified system needs about 26,423 BTU/h of 47°F capacity. 5,548 of the 14,941 certified systems cover that load at 14°F.