Data sources and update log
A calculator is only as good as the data under it. This page shows exactly what is verified and what is not, including the parts that are still unfinished.
Primary sources
| Source | Used for | Access |
|---|---|---|
| NREL PVWatts v8 | Generation estimates from location and system spec |
Public API at developer.nlr.gov. The former
developer.nrel.gov host was retired on 2026-05-29.
|
| OpenEI Utility Rate Database | Electricity tariffs and effective rates | Public API. Curated by NREL and refreshed roughly annually, so records can lag actual utility pricing. |
| EIA Form 861 | Per-utility residential rates, customer counts, net-metered solar and battery counts, and the price per kWh charged by lease and PPA providers | Public annual filing, published as a zip of spreadsheets. Annual, and released roughly eleven months after the year it covers — it is the most recent utility-level data in existence and it is still old. Every figure built from it is labelled with its data year. |
| CPUC Rule 21 register | Contract price and system size of every interconnected system in California, used for the quote check | californiadgstats.ca.gov |
| NYSERDA solar register | The same for New York, refreshed monthly | data.ny.gov |
| DSIRE | State and local incentive programmes | No free public API. Programmatic access is gated behind a subscription enquiry, so our incentive records are compiled by hand from DSIRE's public programme pages and the administering agency, each with a source URL and review date. |
| IRS / statute | §25D expiry and §48E deadline | Encoded once in the model and asserted in the test suite. |
State data status
A state page stays out of search results until both its production data and its incentive record are verified. Publishing a wrong electricity rate into the search index costs more than shipping the page late.
| State | Production & rates | Incentives | Refreshed |
|---|---|---|---|
| California | Verified | Reviewed 2026-08-14 | 2026-08-16 |
| Texas | Verified | Reviewed 2026-08-14 | 2026-08-16 |
| Florida | Verified | Reviewed 2026-08-14 | 2026-08-16 |
| Arizona | Verified | Reviewed 2026-08-14 | 2026-08-16 |
| Massachusetts | Verified | Reviewed 2026-08-14 | 2026-08-16 |
| New York | Verified | Reviewed 2026-08-14 | 2026-08-16 |
| New Jersey | Verified | Reviewed 2026-08-14 | 2026-08-16 |
| Illinois | Verified | Reviewed 2026-08-14 | 2026-08-16 |
| Hawaii | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Georgia | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Nevada | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| North Carolina | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Colorado | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Maryland | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Pennsylvania | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Connecticut | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Rhode Island | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Ohio | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Michigan | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Indiana | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Utah | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Washington | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Oregon | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Minnesota | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Virginia | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| South Carolina | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| New Mexico | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Maine | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| New Hampshire | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Vermont | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Delaware | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| West Virginia | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Wisconsin | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Iowa | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Missouri | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Kansas | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Nebraska | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| North Dakota | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Montana | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Oklahoma | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Arkansas | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Idaho | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| South Dakota | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Alaska | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Alabama | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Mississippi | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Tennessee | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Kentucky | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Louisiana | Verified | Reviewed 2026-08-15 | 2026-08-16 |
| Wyoming | Verified | Reviewed 2026-08-15 | 2026-08-16 |
Production dataset last refreshed 2026-08-16T12:52:22.163Z.
Corrections
If a rate here does not match your bill, that is a bug and we want to know. The Utility Rate Database lagging a utility's actual pricing is the most likely cause, and it is exactly the failure mode we cannot catch alone.
The full set of modelling assumptions is on the methodology page.
Written and maintained by guarledes . Last reviewed 2026-08-14.