Official Resources
The primary sources behind our numbers. When our calculators and your installer disagree, these are the authorities to check.
IRS Guidance on Tax Credits
The IRS is the final authority on federal tax credit eligibility. These pages reflect the 2025 law changes that ended most federal clean energy credits.
- Clean Vehicle Tax Credits
irs.gov
Official guidance on the new (30D) and used (25E) clean vehicle credits, including the September 30, 2025 acquisition deadline and rules for claiming a grandfathered purchase.
- Residential Clean Energy Credit
irs.gov
The 30% credit for solar panels, battery storage, and geothermal that ended December 31, 2025 — including carryforward rules for systems installed before the deadline.
- Energy Efficient Home Improvement Credit
irs.gov
The 25C credit covering heat pumps (up to $2,000) and other efficiency upgrades, which ended for property placed in service after December 31, 2025.
Legislation & Legal Text
Primary sources for the law itself — useful when you want the exact rules rather than a summary.
- H.R. 1 — One Big Beautiful Bill Act (119th Congress)
congress.gov
The July 2025 budget reconciliation law that terminated the federal clean vehicle, residential clean energy, and home improvement credits.
- CRS Report: Expiration of the Residential Clean Energy Credit
congress.gov
Congressional Research Service analysis of the 25D credit's expiration and carryforward rules — the clearest official explainer of what changed for solar and battery buyers.
- 26 U.S. Code § 25D — Residential Clean Energy Credit
law.cornell.edu
The current statutory text from Cornell's Legal Information Institute, reflecting the termination date.
Energy Prices & Vehicle Data
The official datasets behind our calculators' default rates and efficiency figures.
- EIA Weekly Gasoline & Diesel Prices
eia.gov
The U.S. Energy Information Administration's weekly retail fuel price survey — the standard source for national and regional gas prices.
- EIA Electricity Data Browser
eia.gov
Residential electricity rates by state, updated monthly. This is where our state electricity rate data originates.
- FuelEconomy.gov
fueleconomy.gov
EPA/DOE vehicle efficiency ratings for every EV, hybrid, and gas model — including kWh per 100 miles, MPG, and historical tax credit eligibility lists.
Incentive Databases
With federal credits ended, state and utility programs are the main incentives — these databases track what's active where you live.
- DSIRE — Database of State Incentives for Renewables & Efficiency
dsireusa.org
The most comprehensive directory of state, local, and utility clean energy incentives, maintained by NC State University. Our state incentive data is sourced from DSIRE.
- AFDC State Laws & Incentives
afdc.energy.gov
The DOE Alternative Fuels Data Center's state-by-state directory of EV and alternative fuel incentives, laws, and utility programs.
- AFDC Federal EV Tax Credit Reference
afdc.energy.gov
DOE's plain-language reference page for the federal EV tax credit rules and their expiration.
- DOE Home Energy Rebates Programs
energy.gov
The state-administered HOMES and HEEHRA rebate programs for heat pumps and efficiency upgrades — up to $8,000 for income-qualifying households in participating states.
- ENERGY STAR Federal Tax Credit Reference
energystar.gov
ENERGY STAR's equipment-by-equipment reference for which products qualified for federal credits and current efficiency requirements.
Technology Guides
Plain-English explainers from the Department of Energy.
We link only to government, academic, and official program sources. No link on this page is sponsored or affiliated. Found a broken link or a source we should add? Let us know. For how we use these sources in our calculations, see our methodology.