How the calculator models net metering

The policy itself is covered, and kept current, by Virtue Solar's write-up of the 2026 SCC ruling, its report on the Appalachian Power order and its Virginia incentives page. This page is narrower: it explains what the calculator assumes about net metering, why, and what that leaves out.

The one assumption that does most of the work

Your meter runs both ways. When the panels make more than the house uses, the surplus flows to the grid and you earn a credit; at night you draw from the grid and spend credits. Virginia's investor-owned utilities and electric cooperatives credit exported solar at the full retail rate, with credits carried forward for 12 months. The State Corporation Commission's April 30, 2026 ruling on Dominion's net-metering case kept full retail crediting in place. Because a kilowatt-hour you export is worth the same as one you buy, the calculator can skip hourly simulation entirely and treat annual production as offsetting annual usage, up to 100% of it.

What the model does with the rules

• Rollover: credits carry forward for 12 months, so summer surplus pays for winter and the model only needs annual totals.
• Surplus beyond annual usage earns nothing. Utilities now pay something for year-end leftovers (Dominion and Appalachian Power each have a rate for new customers), but it is well below retail, so the calculator sizes to usage and gives surplus a value of zero. Conservative on purpose.
• Fixed charges stay. The basic customer charge, any minimum bill and Dominion's new monthly net-metering fee are not offset by credits. The calculator strips the "fixed monthly charges" input out of the rate it applies to the kWh your panels replace.
• No standby charge, no time-of-use. Residential systems above Dominion's standby threshold (explained here) and time-varying tariffs are outside the model; both are rare for a system sized to a home's usage.
• Sizing cap. Utilities cap net-metered systems at 100–150% of prior-year usage. The calculator's offset slider stops at 100%, so it never designs a system the tariff would reject.

Rules by utility, in brief

• Dominion Energy: Dominion customers enrolling after April 30, 2026 are on the SCC's revised terms: full retail credit for exports, a $1-per-month net-metering administrative fee, year-end excess credits paid out at 5.829 cents per kWh rather than carried forward, renewable-energy certificates kept by the customer, and systems sized up to 150% of the prior 12 months' usage. A standby charge applies to residential systems above 15 kW (rising to 20 kW on January 1, 2027 under 2026's HB 1255). Customers enrolled before the ruling keep their existing terms.
• Appalachian Power: Appalachian Power customers keep full retail crediting under the SCC's August 29, 2025 order. For customers enrolling after that order, credits left over at the end of the 12-month period are paid out at roughly one-third of the retail rate rather than carried forward. Appalachian Power has no residential standby charge.
• Investor-owned cap: For Dominion and Appalachian Power, net metering stays open until enrolled capacity reaches 6% of the utility's adjusted prior-year peak load (5% general plus 1% reserved for low-income customers).
• Cooperatives: Electric cooperatives net meter under a separate section of the statute (§ 56-594.01). Each cooperative's board sets its own program cap, fees and interconnection paperwork, and at least one Virginia cooperative has reached its cap in the past, so check the current tariff before signing.
• Municipal and university utilities: Municipal and university-owned utilities are not covered by Virginia's net-metering statute and set their own policies. Some offer a comparable retail credit, some do not; check the utility's tariff before sizing a system.

Why this matters more than the tax credit did

The federal credit cut the price of a system by 30%. Net metering determines the value of every kilowatt-hour the system produces for 25 years. In a state where the retail price keeps rising, the second is worth more than the first, and it is still in place. States that moved to "net billing" (crediting exports at wholesale rates) saw payback periods lengthen sharply. Virginia has not done that, which is why the calculator's break-even years are what they are.

Practical implications

• Do not oversize. Credits beyond annual usage are worth little.
• Do not undersize out of caution either; every kWh you still buy is at full price.
• East-west roofs produce when you use; south roofs produce the most total. Under 1:1 crediting, total wins.
• Batteries are for outages, not for arbitrage, as long as crediting is 1:1.

Policy details reviewed 2026-10-06. Sources: Virtue Solar — SCC final ruling on Dominion NEM 2.0 (May 2026); Virtue Solar — APCo net metering preserved (Sept 2025); pv magazine — SCC approves Dominion net metering terms (May 2026); Cardinal News — Appalachian Power net metering order (Sept 2025); Code of Virginia § 56-594 (net energy metering).