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. The directory has no bulk export and blocks automated access, so figures from it are looked up and recorded by hand, per model, rather than pulled by a scheduled adapter.
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.
488 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.
27 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.
16 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