In Washington, D.C., a 6.2-kW system for an average home costs about $19,404 after incentives in 2026, saves about $1,968 in the first year and pays back in 8.9 years.
| Item | Amount |
|---|---|
| Solar, 6.16 kW × $3.15/W | $19,404 |
| Federal credit (0%) | $0 |
| Net cost | $19,404 |
| Scenario | Net cost | Year-1 savings | Payback | 25-yr net |
|---|---|---|---|---|
| State averages (above) | $19,404 | $1,968 | 8.9 yr | $48,835 |
| Rates rise 5.6%/yr (2020–25 pace) | $19,404 | $1,968 | 8.2 yr | $76,487 |
| Rates stay flat | $19,404 | $1,968 | 10 yr | $27,713 |
| Survey price $3.6/W (LBNL) | $22,176 | $1,968 | 10 yr | $46,063 |
| Add 13.5-kWh battery | $31,190 | $1,968 | 13.4 yr | $37,049 |
| Exports cut to 50% of retail | $13,860 | $1,005 | 12 yr | $20,414 |
Verdict: at average Washington, D.C. numbers, solar is a solid investment in 2026 — payback takes 8.9 years, leaving you $48,835 ahead after 25 years. The main reasons: electricity that costs more than in all but 9 states; 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 Washington, D.C.: Pepco net metering in kWh credits; year-end excess paid ~14.7¢/kWh.
Battery: a 13.5-kWh battery at the Washington, D.C. average of $873/kWh adds $11,786 and saves almost nothing extra under 1:1 net metering — buy it for backup, not payback; payback becomes 13.4 years.
EnergySage's Washington, D.C. page lists a 5.2-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.