Data Status | What's live, what's static, when it was last refreshed

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 If a value below ever drifts more than a few months out of date, it is fair to challenge whether the corresponding calculator output is still useful.

Free vs paid data choice. DSIRE introduced a paid real-time API in late 2025. We deliberately use the free monthly CSV/XML data dumps published on DSIRE's Resources page — both contain the same underlying program records; only intra-month freshness differs. For a residential-solar reference site, monthly is sufficient.

Summary

Dataset	Snapshot	Next review
State electricity rates	May 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

All five datasets currently use the manual snapshot method. Automated sync scripts for EIA electricity rates and NREL solar resource data have been built and are ready to activate once API keys are registered. Until then, the operator reads the cited source and updates the configuration files in the codebase. This is intentional disclosure — earlier versions of the site implied automated freshness it did not have.

Roadmap to live data

Three of the five datasets can be refreshed automatically. Automated sync scripts for EIA electricity rates and NREL solar data have been built and tested; they will be activated once the operator registers for free API keys from each agency.

Dataset	Live-feed mechanism	Effort	Status
State electricity rates	EIA Open Data API (api.eia.gov), free API key	~1 day	Built. Automated sync script ready; awaiting API key registration.
Peak sun hours	NREL Solar Resource Data API (developer.nrel.gov), free API key	~1 day	Built. Automated sync script ready; awaiting 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.

Per-dataset detail

State electricity rates

Source: U.S. Energy Information Administration (EIA), Electric Power Monthly, Table 5.6.A
URL: https://www.eia.gov/electricity/monthly/epm_table_grapher.php?t=epmt_5_6_a
License: Public domain (US federal government work)
Snapshot date: May 2025
Next review: 2026-08
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: EnergySage Solar Marketplace Report (H2 2024 median); SEIA/Wood Mackenzie US Solar Market Insight (Q3 2024); NREL US Solar PV System Cost Benchmark (Q1 2024)
URL: https://www.energysage.com/data/
License: Cited under fair use for educational summary
Snapshot date: May 2025
Next review: 2026-08
Note: Midpoint of three publicly-available market trackers. Actual installer quotes vary ±30%.

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: May 2025
Next review: 2026-08
Note: Sample programs only. A DSIRE CSV importer exists but is not run on a fixed schedule. For the authoritative current list, consult DSIRE directly.

Reporting an issue

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.

Data status.

Summary

Roadmap to live data

Per-dataset detail

State electricity rates

Peak sun hours by state

Federal Residential Clean Energy Credit

Installed cost per watt (residential)

State and utility incentives

Reporting an issue

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