GetSolarCalc
Transparency Last reviewed Sep 18, 2026

Data status.

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.

Why this page exists. A residential solar payback estimate is only as fresh as the data behind it. Rather than asking visitors to trust an opaque pipeline, we publish the actual state of every dataset here. If a value below ever drifts more than a few months out of date, it is fair to challenge whether the corresponding calculator output is still useful.
The free DSIRE archive no longer exists. This site was built to read DSIRE's free monthly CSV/XML dumps. As of our check on 18 September 2026 that archive is not linked anywhere on dsireusa.org, and DSIRE's data-access page states the API is for subscribers; scripted requests return HTTP 403 with a licensing notice. So there is currently nothing feeding the importer automatically. The states we list were read by hand from the public per-state pages, and every state now carries the date it was checked, so a state with no programmes is a finding rather than a gap in our coverage.

Summary

DatasetSnapshotNext review
State electricity rates 2025 Dec 2026
Peak sun hours by state May 2025 May 2027
Federal Residential Clean Energy Credit June 2026 Dec 2026
Installed cost per watt (residential) 2025 Sep 2027
State and utility incentives September 2026 Mar 2027

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.

Roadmap to live data

Two of the five datasets can be refreshed automatically. The EIA electricity rate sync is live; NREL solar data will follow once the operator registers for a free API key. The incentives feed was a third until DSIRE withdrew its free archive, and is now hand-compiled — the honest status is blocked, not pending.

DatasetLive-feed mechanismEffortStatus
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 Was the free DSIRE CSV archive; that archive is no longer published. The remaining route is the paid DSIRE Insight subscriber feed. Manual Blocked. Importer works; no source to feed it. Compiled by hand, state by state.
Cost-per-watt No public API; Berkeley Lab publishes Tracking the Sun once a year, each August Manual Reviewed annually, on publication. Next: September 2027.
Federal credit Statutory law; changes only on Congressional amendment Manual Reviewed on every IRS rule change.

Per-dataset detail

State electricity rates

Source
U.S. Energy Information Administration (EIA), Open Data API v2, electricity/retail-sales — residential sector, annual average price
URL
https://www.eia.gov/opendata/browser/electricity/retail-sales
License
Public domain (US federal government work)
Snapshot date
2025
Next review
2026-12
Note
Static state-level approximations. Real residential rates vary by utility and tariff. For your actual rate, check your utility bill or EIA Form 826.

Peak sun hours by state

Source
NREL National Solar Radiation Database (NSRDB), population-weighted state averages
URL
https://nsrdb.nrel.gov/
License
Public domain (US federal government work)
Snapshot date
May 2025
Next review
2027-05
Note
NSRDB values are stable year-to-year. For site-specific values use NREL PVWatts.

Federal Residential Clean Energy Credit

Source
26 U.S.C. § 25D, as amended by IRA §13302 (P.L. 117-169, 2022)
URL
https://www.law.cornell.edu/uscode/text/26/25D
License
Public domain (federal statute)
Snapshot date
June 2026
Next review
2026-12
Note
Current IRS guidance says the credit is not available for new residential clean-energy expenditures after December 31, 2025. Older qualifying installations may still have carryforward issues.

Installed cost per watt (residential)

Source
Lawrence Berkeley National Laboratory, Tracking the Sun / U.S. Distributed Solar and Storage 2026 Data Update (August 2026) — national residential PV-only, cash-purchase median and 20th/80th percentiles, 2025 installations (N=18,361)
URL
https://emp.lbl.gov/tracking-the-sun
License
Public domain (US Department of Energy national laboratory work)
Snapshot date
2025
Next review
2027-09
Note
Median price actually paid by cash purchasers for residential PV in 2025, before any incentives, from Berkeley Lab's project-level dataset rather than a modelled estimate. Half of cash buyers paid more. The quoted range is the 20th to 80th percentile, so one buyer in five paid above it — spread this wide is why the calculator is a quote-checking baseline and not a quote.

State and utility incentives

Source
DSIRE® (Database of State Incentives for Renewables & Efficiency), NC Clean Energy Technology Center, NC State University
URL
https://www.dsireusa.org/
License
Creative Commons BY-SA 4.0
Snapshot date
September 2026
Next review
2027-03
Note
Hand-compiled from the public DSIRE per-state pages. All 51 states (50 plus DC) have now been read, each carrying the date it was checked: 37 have at least one programme a homeowner can use, and 14 were checked and genuinely have none. Programme terms, budgets and eligibility change between reviews — several entries here record a cap, a cut-off date or a closed funding round — so confirm any figure with the administering agency before relying on it.

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