In Montana, a 7-kW system for an average home costs about $17,811 after incentives in 2026, saves about $1,446 in the first year and pays back in 10.7 years.
| Item | Amount |
|---|---|
| Solar, 7.04 kW × $2.53/W | $17,811 |
| Federal credit (0%) | $0 |
| Net cost | $17,811 |
| Scenario | Net cost | Year-1 savings | Payback | 25-yr net |
|---|---|---|---|---|
| State averages (above) | $17,811 | $1,446 | 10.7 yr | $32,465 |
| Rates rise 5.6%/yr (2020–25 pace) | $17,811 | $1,446 | 9.7 yr | $52,822 |
| Rates stay flat | $17,811 | $1,446 | 12.5 yr | $16,905 |
| Survey price $3.6/W (LBNL) | $25,344 | $1,446 | 14.5 yr | $24,933 |
| Add 13.5-kWh battery | $32,864 | $1,446 | 18 yr | $17,413 |
| Exports cut to 50% of retail | $12,245 | $711 | 14.5 yr | $11,991 |
Verdict: at average Montana numbers, solar is a solid investment in 2026 — payback takes 10.7 years, leaving you $32,465 ahead after 25 years. The main reasons: cheap power (the 11th-lowest price of 51), which caps what each kWh saves; 1:1 net metering, which credits every exported kWh at the full retail price. 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 Montana: IOU net metering in kWh credits; unused credits surrendered after 12 months.
Battery: a 13.5-kWh battery at the Montana average of $1,115/kWh adds $15,053 and saves almost nothing extra under 1:1 net metering — buy it for backup, not payback; payback becomes 18 years.
EnergySage's Montana page lists a 17.4-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.