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Solar panels in Boston, MA

Every figure below is produced by simulating a full year — 8,760 hours — of sun angles, cloud cover, air temperature and wind for Boston, then running the result through a panel and inverter model. No rules of thumb.

1,278kWh per kW / year
8,946kWh from a 7 kW roof
0.814performance ratio

What a system actually produces here

Solar output in Boston peaks in July and bottoms out in November, a swing of about 2.1×. That seasonal shape matters more than the annual total if your utility settles exports monthly rather than annually — a big summer surplus can be worth much less than the same energy spread evenly.

MonthSun (kWh/m²/day)kWh per kW7 kW system
Jan1.977539
Feb2.787612
Mar3.8116815
Apr4.7124869
May5.5136954
Jun5.9134939
Jul5.9137962
Aug5.2128894
Sep4.3112785
Oct3.094659
Nov1.965455
Dec1.666463

Electricity rates that shape the payback

What a solar system saves in Boston depends less on how much it produces than on when it produces, and what your utility pays for the surplus. These are the MA schedules modelled by the calculator:

Eversource / National Grid — Residential R-1 + SMART

Full retail net metering AND a 20-year production incentive on top. The richest stack left in the country. Fixed charge $10.00/month. Summer Flat $0.30. Winter Flat $0.29.
Source: MA residential rates; DOER SMART 3.0 program, residential ≤25 kW

Export rule: Eversource / National Grid — full net metering — every exported kilowatt-hour is credited at the same retail price you pay to import one. Under net billing, exported kilowatt-hours earn far less than the retail price you pay to import them — which is why self-consumption and batteries change the maths so much. The calculator settles every hour individually rather than netting annually.

Run your own numbers

Payback depends on what you pay for the system, how much power your household uses after dark, and which incentives you qualify for — none of which a city page can know. The calculator asks for those and settles all 8,760 hours against your actual rate.

Open the payback calculator

See also: solar incentives in Massachusetts — the state credit, the export rules, and what the §25D expiry changed for buyers here.

Other cities

Method

Irradiance is decomposed into beam and diffuse components and projected onto the array plane with the Perez model, with incidence-angle losses, a cell-temperature model driven by air temperature and wind, and an inverter efficiency curve including clipping. Annual yield is checked against NREL PVWatts v8 across all 18 modelled cities; RMS error is 2.70%. See the glossary for what each term means.