In Massachusetts, a 5.7-kW system for an average home costs about $15,588 after incentives in 2026, saves about $2,383 in the first year and pays back in 6.1 years.
| Item | Amount |
|---|---|
| Solar, 5.72 kW × $2.9/W | $16,588 |
| Federal credit (0%) | $0 |
| State incentive | −$1,000 |
| Net cost | $15,588 |
| Scenario | Net cost | Year-1 savings | Payback | 25-yr net |
|---|---|---|---|---|
| State averages (above) | $15,588 | $2,383 | 6.1 yr | $64,893 |
| Rates rise 5.6%/yr (2020–25 pace) | $15,588 | $2,383 | 5.8 yr | $95,853 |
| Rates stay flat | $15,588 | $2,383 | 6.6 yr | $41,235 |
| Survey price $3.4/W (LBNL) | $18,448 | $2,383 | 7.1 yr | $62,033 |
| Add 13.5-kWh battery | $33,840 | $2,383 | 12.2 yr | $46,641 |
| Exports cut to 50% of retail | $10,484 | $1,244 | 7.8 yr | $29,613 |
Verdict: at average Massachusetts numbers, solar is a strong investment in 2026 — payback takes 6.1 years, leaving you $64,893 ahead after 25 years. The main reasons: electricity that costs more than in all but 3 states; 1:1 net metering, which credits every exported kWh at the full retail price; a state incentive worth about $1,000; performance payments (SMART 3.0 base incentive (about $0.03/kWh; EnergySage lists 20 years)). Pay cash if you can: Berkeley Lab found loan-financed systems priced about $1.50/W above cash installs in 2025, which can add years to the payback.
Net metering and exports in Massachusetts: Net metering for inverters <25 kW (IOUs); municipal utilities may not offer it.
Battery: a 13.5-kWh battery at the Massachusetts average of $1,352/kWh adds $18,252 and saves almost nothing extra under 1:1 net metering — buy it for backup, not payback; payback becomes 12.2 years.
EnergySage's Massachusetts page lists a 7-year payback. Its method is not fully published; ours uses EIA's Jan–Aug 2026 price, 1:1 net metering, 3%/yr rate growth and 0.5%/yr panel aging, with no federal credit.
The full method, material data and tips are on the main solar payback calculator page.