Methodology & editorial policy
How we track plug-in solar laws, where our data comes from, and every assumption behind our savings estimates.
Last updated
How we track state laws
Each of the 51 state pages (50 states plus DC) carries a status, and where applicable a bill number, signing date, effective date and wattage cap.
| Status | Meaning |
|---|---|
| Law | A plug-in solar bill has been signed by the governor. It may not be in force yet — check the effective date. |
| Awaiting | Both chambers passed a bill; the governor has not yet acted. |
| Advancing | A bill is alive in the legislature (in committee or passed one chamber). |
| Stalled | A bill was introduced but did not pass before the session ended. |
| Defeated | A bill was killed, stripped of plug-in provisions or postponed indefinitely. |
| No bill | No plug-in solar legislation has been introduced. |
Sources. We rely on signed bill texts and legislature records where available, on reporting by trade and local press (pv magazine USA, Canary Media, Solar Power World, local public radio and newspapers), and on legislative trackers maintained by nonprofit advocates. Each state page lists the sources used.
Verification. Every state page shows a "last verified" date. We re-check states with active legislation at least weekly during legislative sessions and immediately after reported signings.
Conflicts. When sources disagree — signing dates reported a few days apart are common — we prefer official legislature records, then contemporaneous local reporting, and we note uncertainty in the text.
How we estimate savings
Our calculator and the estimates on state pages use this model:
Annual production (kWh) = system size (kW) × peak sun hours × 365 × orientation factor × mounting factor × 0.86
Annual savings ($) = annual production × share used at home × electricity rate
Inputs
- Electricity rate: each state's average residential price from the U.S. Energy Information Administration, Electric Power Monthly, Table 5.6.A, July 2026. Your actual tariff — especially time-of-use or tiered rates — may be higher or lower.
- Peak sun hours: long-term annual averages for a south-facing panel tilted near latitude, rounded to one decimal and based on NREL solar resource data. Local shading and weather can move this considerably.
- System efficiency (0.86): combines inverter conversion, wiring, temperature and soiling losses — a standard assumption in residential solar modeling.
Orientation and mounting factors
| Orientation | Factor |
|---|---|
| South | 1.00 |
| South-east / south-west | 0.95 |
| East / west | 0.82 |
| North | 0.58 |
| Mounting | Factor |
|---|---|
| Tilted ~30° | 1.00 |
| Flat (0–10°) | 0.88 |
| Vertical railing | 0.70 |
These are simplified planning factors. Vertical panels perform relatively better in winter and at high latitudes, and worse in summer.
Self-consumption
Plug-in systems are exempt from net metering under every state law we track, so electricity you export earns nothing. We default to 80% of production being used at home, which is typical for an 800 W system in a household with a refrigerator, networking gear and other always-on loads. With a battery, 95% or more is realistic.
Other defaults
- Kit cost: $900 for 800 W, $1,300 for 1,200 W (complete kits with certified microinverter and mounting, before any discounts).
- Lifetime: 25 years, without degradation or rate inflation (two effects that roughly offset each other over time).
- CO₂: 0.81 lb per kWh, approximating the US grid average from EPA eGRID.
Corrections
We correct errors promptly and note material corrections on the page. Email contact@plugshine.com.
Independence
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