Source registry
Every source our data comes from, what it is trusted for, and where it sits in our authority ranking. Tier 1 outranks tier 5 in every conflict.
Tier 1 — Regulatory and certification bodies
AHRI Directory of Certified Product Performance
Air-Conditioning, Heating & Refrigeration Institute · www.ahridirectory.org/
The legal system of record for HVAC ratings in the US. A rated combination must be AHRI-certified for efficiency claims, rebates, and code compliance. Performance figures here override all others.
0 published values sourced from here
ENERGY STAR Certified Product Lists
US EPA · www.energystar.gov/productfinder
Published as Socrata open-data endpoints on data.energystar.gov. Machine-readable, versioned, and authoritative for certification status and the efficiency metrics EPA verifies.
0 published values sourced from here
DOE Office of Energy Efficiency & Renewable Energy
US Department of Energy · www.energy.gov/eere/
Federal minimum efficiency standards, regional standards, and test-procedure definitions (SEER2/HSPF2/UEF).
0 published values sourced from here
IRS energy credit guidance
Internal Revenue Service · www.irs.gov/
Controlling authority on federal tax credit eligibility.
0 published values sourced from here
IECC Climate Zone Map
International Code Council / DOE Building America · basc.pnnl.gov/images/iecc-climate-zone-map
Defines the climate zones that drive equipment selection.
0 published values sourced from here
EIA energy price data
US Energy Information Administration · www.eia.gov/
Official US energy price series. Has a free JSON API (api.eia.gov).
0 published values sourced from here
Tier 2 — Independent technical organisations
NEEP Cold Climate Air Source Heat Pump List
Northeast Energy Efficiency Partnerships · ashp.neep.org/
The single best source for cold-weather heat pump performance. Publishes capacity and COP at 47F, 17F and 5F -- the numbers that actually determine whether a heat pump works in a cold climate. AHRI ratings alone do not test below 17F.
11 published values sourced from here
NREL research and PVWatts
National Renewable Energy Laboratory · www.nrel.gov/
Solar production modeling and cost benchmarks.
0 published values sourced from here
California Energy Commission equipment lists
California Energy Commission · www.energy.ca.gov/
Independently verified solar module and inverter performance data.
0 published values sourced from here
DSIRE incentive database
NC Clean Energy Technology Center · www.dsireusa.org/
Most complete registry of state and utility energy incentives.
0 published values sourced from here
Rewiring America incentive guides
Rewiring America · homes.rewiringamerica.org/
Tracks federal and state incentive status closely and updates fast.
0 published values sourced from here
Tier 3 — Manufacturer documentation
Manufacturer submittal and specification sheets
Various
Authoritative for physical specs, warranty terms and operating limits. Treated with caution for efficiency claims, which are marketed selectively -- prefer AHRI or NEEP where both exist.
532 published values sourced from here
HVAC wholesale/distributor product pages
Various (Ferguson, WalkAirDirect, Alpine Home Air, HVACDirect, Ingrams Water & Air, Gemaire, GSHA Services)
Distributor/contractor-supply product pages that republish manufacturer spec-sheet data (model numbers, SEER2, sound, refrigerant, warranty terms) verbatim, and sometimes carry equipment-only sell prices the manufacturer itself never publishes. Treated one tier below mfr_docs proper because the spec transcription is third-party, not the original document -- prefer mfr_docs or AHRI where the same figure is available there.
30 published values sourced from here
Portlandia Electric Supply product pages
Portlandia Electric Supply · www.portlandiaelectric.supply/
Real distributor product pages that republish manufacturer spec sheets in detail, including UL certification listings, and carry real per-unit prices.
2 published values sourced from here
Outbound Power product pages
Outbound Power · outboundpower.com/
Real retailer selling Bluetti fixed/panel-integrated home battery configurations with published per-unit pricing and spec tables.
4 published values sourced from here
Tier 4 — Independent editorial
EnergySage equipment guides
EnergySage · www.energysage.com/
Independent marketplace with real installed-cost data. Good for pricing context; secondary for performance figures.
56 published values sourced from here
OBBBA energy credit analysis
PKF O'Connor Davies · www.pkfod.com/insights/updates-to-energy-cr...
Accounting-firm analysis of the 2025 tax law changes.
0 published values sourced from here
Third-party HVAC installed-price estimators
Various (HomeGuide, PickHVAC, FurnacePrices.ca)
Aggregated/blended installed-cost estimates, usually by brand or tonnage band rather than by exact SKU. Weaker than energysage's real marketplace transactions -- these read as compiled estimates, not observed sales -- so used only where no better price source exists, and never for anything but the price fields.
20 published values sourced from here
Choose Energy state rate tables
Choose Energy · www.chooseenergy.com/
Republishes EIA state price data in an accessible table. Used as a convenience layer over EIA; replaced by the EIA API adapter when run with network access.
0 published values sourced from here
YouTube video transcript capture
YouTube · www.youtube.com/
Full transcript, description and comment text captured by hand via real browser review (the 'Show transcript' panel), not the Data API. Stored so an evidence claim can be re-checked or re-analyzed later against the exact document it was written from, without re-fetching. This is a research/internal snapshot only -- what actually appears on the site is still governed by the 'youtube' evidence platform's quote and redistribution policy in evidence.py; the full transcript itself is never published.
0 published values sourced from here
HomeSystems editorial assessment
HomeSystems
Our own analysis and synthesis. Used only for judgement fields (who a product suits, what to watch out for) -- never for measured performance values.
37 published values sourced from here
LeafScore heat pump water heater comparison
LeafScore · www.leafscore.com/energy-efficient/the-10-b...
Aggregates published UEF and first-hour ratings for heat pump water heaters.
14 published values sourced from here
Solar module efficiency and degradation comparison
PowMr Community · community.powmr.com/insights/best-solar-pan...
Compiles datasheet efficiency, degradation and temperature coefficient figures across current residential modules.
22 published values sourced from here
Home battery specification comparison
PowerLutions · powerlutions.com/battery-storage/2026-batte...
Installer-published comparison of usable capacity, continuous output and warranty terms for current home batteries.
12 published values sourced from here
Submersible well pump comparison
WellDrillingCosts.com · welldrillingcosts.com/guides/grundfos-vs-fr...
Trade-oriented comparison including flow, head, horsepower and observed field failure patterns.
19 published values sourced from here
PumpProducts.com catalog listings
PumpProducts.com · www.pumpproducts.com/
Wholesale/retail pump catalog that republishes manufacturer spec-sheet figures (stages, GPM, max head) per SKU; used here for a field correction, cross-checked against a second independent retailer.
1 published value sourced from here
EnergySage battery equipment/review pages
EnergySage · www.energysage.com/energy-storage/
Marketplace/comparison site republishing manufacturer specs in structured form. Two real, disclosed data-entry issues found this pass on this exact source (a continuous/peak power swap on sonnen sonnenCore+ 10; an inflated round-trip-efficiency figure elsewhere) -- cross-check against a second source before treating a single EnergySage figure as decisive.
1 published value sourced from here
SolarTechOnline product guides
SolarTechOnline · solartechonline.com/
Independent editorial buying-guide site. Used this pass for chemistry and warranty details not found on the manufacturer's own page for a specific sub-model (LG RESU16H Prime); also the source that correctly flagged both the SunPower SunVault and Panasonic EverVolt discontinuations before this pass found independent corroboration.
2 published values sourced from here
SolarReviews expert review articles
SolarReviews · www.solarreviews.com/blog/
Named-author editorial reviews. Used this pass for the Anker SOLIX X1 warranty terms and an explicitly-labeled editorial price ESTIMATE (not used as a price_seed observation) after confirming Anker itself does not publish a price.
1 published value sourced from here
Tier 5 — Retail listings
Amazon Product Advertising API
Amazon · webservices.amazon.com/paapi5/documentation/
Aggregate star rating, review count and a deep link only -- Amazon's terms prohibit scraping and PA-API does not return review bodies. Treated as weak evidence: see amazon.py's module docstring.
0 published values sourced from here