Solar Calculators for Washington, DC

Free tools with illustrative Washington planning inputs. Replace energy rates and installation costs with your bill and written quote.

Quick answer

Start with your exact utility account and roof design. The 4.3 sun hours and 15.0 cents/kWh below are planning assumptions, not verified current rates for Washington. Confirm Pepco eligibility and export settlement.

Notes updated 2026-07-26

Best for: Washington homeowners comparing a proposal or estimating savings before calling installers.
Inputs needed: 12-month kWh usage, roof shade, Pepco, quoted $/W
Formula used: Local production = system kW × local peak sun hours × 365, then adjusted for losses.
Method references: NREL PVWatts, Pepco, DC incentive rules

Peak sun hours

4.3

hrs/day planning assumption

Illustrative energy rate

15.0¢

per kWh (Pepco)

Typical install cost

$3/W

planning assumption, not a market median

Net metering policy: Full retail net metering ✓

What Washington homeowners should check

Washington rowhouses and compact urban roofs often face shading, parapets, rooftop equipment, and fire-access constraints. A site-specific layout and roof-condition review are essential before using the full roof area in a production estimate.

Pepco manages local interconnection. DC incentive value can be meaningful, so contract language should state who registers the system, owns any certificates, and handles ongoing reporting.

What should I verify before signing a solar contract in Washington?

Confirm that the quote names your actual utility, uses a recent electricity rate, includes measured shade and roof-condition findings, and explains who handles permits and interconnection. Ask the installer to separate guaranteed equipment and workmanship terms from estimated production, incentives, and savings.

Illustrative 8 kW system in Washington

Annual production

10,788 kWh

Retail-value ceiling

$1,618

System cost (est.)

$24,000

Energy-only cost/value ratio

~15 yrs

Illustrative 4.3 peak sun hours, 14.08% production losses, 15.0 cents/kWh and $3/W. The retail-value ceiling assumes every kWh earns retail value; lower export credits reduce it. The cost/value ratio is not a full payback model and excludes repairs, financing and rate changes. No new Section 25D homeowner credit in 2026.