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. |
| 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.