Methodology & Data Sources

Every number on PVFig comes from a named public source with an as-of date. If we cannot verify a figure, we say so or leave it out. This page explains how the calculators work and where the data comes from — so you can trust (and check) the results.

How the ROI calculation works

The Solar ROI Calculator computes, for your inputs (state, system size, cost per watt, usage, self-consumption): annual production from the state's PVWatts figure, annual bill savings from your rate and self-consumption, export income (or avoided-cost credit) from the state's net metering classification, plus SREC or incentive income where applicable. It then projects 25 years of cash flow with 3% rate escalation and 0.5% degradation to derive payback period, 25-year net profit, and IRR.

Assumptions (stated, not hidden)

• Reference system: 6 kW DC, $3.00/W installed cost (national median range for 2026; your quote will vary).
• Self-consumption: 70% of production offsets your bill; 30% is exported.
• Rate escalation: 3%/year on the avoided electricity cost.
• Panel degradation: 0.5%/year over a 25-year horizon.
• No federal residential tax credit: Section 25D expired December 31, 2025 and is NOT included.
• State incentives included only where verified: income tax credits, upfront rebates, and SREC income are added when the program is currently open.

Primary data sources

• U.S. Energy Information Administration (EIA) — Average residential electricity rates by state (cents/kWh).
  Table 5.6.B, monthly average revenue per kWh. We use the latest full-month value at each update.
  www.eia.gov/electricity/monthly/
• NREL PVWatts (v8) — Annual solar production per installed kW by state (kWh/kW).
  Derate-adjusted AC production for a fixed-tilt rooftop array at each state’s reference location.
  pvwatts.nrel.gov/
• DSIRE (Database of State Incentives for Renewables & Efficiency) — State incentives: tax credits, rebates, SREC markets, net metering rules.
  Each state entry in our guides cites the current DSIRE program summary, with an as-of month/year.
  www.dsireusa.org/
• State statutes & public utility commissions — Net metering / net billing classification and export credit values.
  We classify each state as full-retail net metering, net billing (partial export credit), or avoided cost based on the latest published utility commission rules.
  www.dsireusa.org/

Update cadence

• Electricity rates: updated monthly after each EIA release (typically ~mid-month for the prior month).
• Net metering / net billing policy: reviewed quarterly and on any announced policy change.
• Incentives (DSIRE): reviewed quarterly; program openings/closures noted on the state guides.
• SREC market prices: indicative ranges, reviewed quarterly (they move with supply and program caps).

What this site is not

PVFig is an educational estimator. It is not a quote, not engineering, and not tax or financial advice. Actual pricing depends on your roof, installer, market, and financing. Always verify with a licensed installer, your utility, and a tax professional before signing anything.