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Fairfax County Dominion

Solar panels in Great Falls, Virginia: 1,374 kWh per kW per year

A south-facing kilowatt of panels in Great Falls makes about 1,374 kWh a year, 0.6% above the Virginia median. Power here comes from Dominion Energy at 15.20¢ per kWh (2025 average).

1,374

kWh / kW / year

PVWatts, south-facing

4.88

Peak sun hours / day

annual average irradiance

10,992

kWh / yr from 8 kW

a common home system

15.20¢

Dominion price

2025 residential avg

Monthly solar production per kW in Great Falls, VirginiaKilowatt-hours per month for a 1 kW south-facing system. Peak in Jul, low in Dec.050100150Jan98Feb88Mar125Apr118May130Jun138Jul142Aug135Sep118Oct113Nov90Dec81
NREL PVWatts v8, 1 kW DC, fixed roof mount, azimuth 180°, tilt 25°, 14% losses. Jul makes about 1.8× Dec.

Seasonality

Monthly solar production in Great Falls

Virginia net metering carries excess credits forward for 12 months, so Jul's surplus offsets Dec's shortfall. Systems are sized to annual usage rather than to the lowest month. How the calculator models net metering; the current rules by utility are on this Virginia incentives page, maintained by the installer behind this site.

Capacity factor: 15.7%. Elevation about 109 m. Compare every town on the city list, or see how roof direction, tilt and shade change the number.

Payback in Great Falls

Solar cost and payback for an average home in Great Falls

Assumes 1,038 kWh a month (≈ $158) at Dominion Energy's 2025 average price, Great Falls's PVWatts production, 3% annual rate growth and $2.78/W installed, no federal credit. Dollars are nominal. Change any of it in the calculator, or compare every utility in Are solar panels worth it in Virginia?

Run it with your bill

9.1 kW

System size

$25,298

Est. cost

$2,073

Year-1 savings

11.1 yrs

Break-even

$62,195

25-yr savings

$36,897

Net benefit

undiscounted

Utility

Electric utilities serving Fairfax County

UtilityTypeAvg price ¢/kWhAvg kWh / monthData year
Dominion EnergyInvestor-owned utility15.201,0382025*

Questions

Questions about solar in Great Falls

How much electricity does a solar system produce in Great Falls?
About 1,374 kWh per year for every kilowatt of panels on a south-facing roof, according to NREL's PVWatts. An 8 kW system would make roughly 10,992 kWh a year. East- or west-facing roofs make less; the calculator applies those factors.
Who is the electric utility in Great Falls?
Dominion Energy serves Great Falls, per EIA's service-territory data. Dominion's 2025 average residential price was 15.20¢ per kWh.
Is solar worth it in Great Falls?
For an average Dominion home (1,038 kWh a month), the default assumptions give a 9.1 kW system costing about $25,298 with a break-even around 11.1 years and $36,897 net benefit (nominal) over 25 years. Your bill, roof and shade change that; the calculator lets you enter them. The statewide picture is in “Is solar worth it in Virginia?”.
Where does the sun data come from?
NREL PVWatts v8 (8.5.0), using the 1137224.csv typical-year weather dataset for grid cell 1137224, about 0 km from the town center. Inputs: 1 kW DC, fixed roof mount, 180° azimuth, 25° tilt, 14% system losses. Typical-year data doesn't change year to year.

Solar production in towns near Great Falls

Sources: NREL PVWatts v8 (8.5.0, typical-year weather); EIA Form 861 2025 utility data and service territories; U.S. Census Bureau place coordinates. Formulas and assumptions on the methodology page.