Core sources
U.S. Energy Information Administration (EIA)
Residential electricity prices, state-level energy statistics and electricity-market reference data.
EnergySage Marketplace
Current residential solar installed-price benchmarks used as external comparison points for state hubs and the Solar Quote Analyzer. These marketplace averages remain separate from Home Solar Atlas homeowner-submitted quote data.
National Laboratory of the Rockies PVWatts
Location-specific photovoltaic energy-production estimates used by ZIP-level production tools and independent first-year production reference checks.
OpenEI
Utility Rate Database records, distributed-generation tariff references and renewable-energy incentive information.
Google Solar API
Building-level roof geometry, sunshine and panel-layout data where coverage is available.
Google Maps Platform Places
Live local business discovery used by the installer finder. These results are not treated as Home Solar Atlas verified profiles.
IRS and government agencies
Federal tax and policy rules, effective dates and official program guidance.
State agencies and electric utilities
Current rebates, tariffs, net metering or net billing rules, interconnection requirements, export limits and program documents.
Equipment manufacturers
Current solar panel, inverter and home battery specifications, warranties, datasheets and compatibility information.
Homeowner / installer proposal documents
User-supplied proposal PDFs are treated as the primary source for quoted price, system size, stated production, financing terms and explicit sales or contract assumptions. Detected PDF values remain review-only until checked against the original document.
Home Solar Atlas calculations are not external sources
Some proposal-review results are deterministic arithmetic built by Home Solar Atlas rather than values imported from a third-party dataset. Examples include panel count × module wattage, DC system size ÷ inverter AC capacity, annual production ÷ annual household usage, financing-premium arithmetic and contract-escalator compounding. These calculations use the user-entered or explicitly detected inputs shown on the page.
When an external reference is used, we label it separately. For example, the Production Claim Checker distinguishes an installer's stated first-year kWh from the NLR PVWatts or state planning reference instead of blending both into one opaque score. See the full methodology for model boundaries and limitations.
How source conflicts are handled
When sources disagree, we prefer the source with direct authority over the specific value: a utility tariff over a statewide average for that utility customer, an agency program document over a marketing summary, a current manufacturer datasheet over an older third-party specification table, and the signed or current proposal document over an automatically detected PDF field.
Market-price benchmarks
External marketplace averages are comparison tools, not Home Solar Atlas market indexes. Where a current state-level solar-price benchmark is published, we use that state figure. Where it is not available, the tool falls back to the current U.S. marketplace average and labels that fallback explicitly.
Proposal-document extraction
Proposal PDF extraction uses deterministic pattern matching on selectable text. It is designed to surface likely values for homeowner review, not to replace the original contract or financing disclosure. Image-only PDFs are not currently OCR-processed. Explicitly detected assumptions can be passed to focused review tools only when the destination has a defined numeric handoff; missing destination inputs remain blank instead of inheriting demo values.
Freshness
Fast-changing data such as electricity prices, solar pricing, incentives, tariffs and news require more frequent review than physical equipment specifications or long-lived methodology. Pages should show source or review dates where the date materially affects the homeowner decision.
Original Home Solar Atlas data
Homeowner-submitted solar quotes are stored separately from third-party datasets. New submissions are moderated before they are included in public aggregate statistics. State averages and example quotes are not published until at least three approved submissions are available for that state, and public examples do not expose ZIP codes, street addresses or homeowner contact information.