The most important page on this site. For each dataset we use, this page records: where it comes from, when we last keyed it in, and whether the refresh is automatic or manual.
| Dataset | Snapshot | Next review |
|---|---|---|
| State electricity rates | Jan 2025 | Aug 2026 |
| Peak sun hours by state | May 2025 | May 2027 |
| Federal Residential Clean Energy Credit | Jun 2026 | Dec 2026 |
| Installed cost per watt (residential) | May 2025 | Aug 2026 |
| State and utility incentives | May 2025 | Aug 2026 |
The EIA electricity rate dataset is now refreshed via the EIA Open Data API v2, activated on July 23, 2026. The remaining four datasets use manual snapshots. NREL solar resource data will be synced via API once the operator registers for a free NREL API key.
Three of the five datasets can be refreshed automatically. The EIA electricity rate sync is now live. NREL solar data will follow once the operator registers for a free API key.
| Dataset | Live-feed mechanism | Effort | Status |
|---|---|---|---|
| State electricity rates | EIA Open Data API (api.eia.gov), free API key | ~1 day | Live. First sync completed July 23, 2026. 49 state rates updated. |
| Peak sun hours | NREL Solar Resource Data API (developer.nrel.gov), free API key | ~1 day | Built. Awaiting NREL API key registration. |
| State incentives | DSIRE monthly CSV archive (dsireusa.org), free download | ~2 hours / month | Importer exists, schedule does not. |
| Cost-per-watt | No public API; depends on quarterly reports being released and read | Manual | Manual review every ~6 months. |
| Federal credit | Statutory law; changes only on Congressional amendment | Manual | Reviewed on every IRS rule change. |
If a value below is materially out of date, please report it via the contact form. Specific corrections (with a link to the current value in the cited source) are easier to act on than general comments.
Four inputs. Sixty seconds. Every number traceable to a public source.