Citations & Data Sources
Every number GainTally produces is traceable to a specific authoritative source. This page lists all federal agencies, state utility commissions, industry bodies, and data providers we rely on — organized by category and listed alphabetically within each group. Transparency about our sources is a core part of our commitment to independent, bias-free clean energy information.
Source list updated: May 2026(may be outdated)
Federal Agencies
U.S. government agencies that provide the primary data powering our calculators.
- DOE— U.S. Department of Energy
- Energy efficiency standards & incentive program guidance
- EIA— U.S. Energy Information Administration
- State-level electricity & natural gas rate data (open API)
- EPA— U.S. Environmental Protection Agency
- Carbon intensity factors & ENERGY STAR program oversight
- IRS— Internal Revenue Service
- Federal clean energy tax credit rules (Form 5695, ITC guidance)
- NREL— National Renewable Energy Laboratory
- Solar irradiance data & PVWatts API (zip-code-level solar estimates)
State Utility Commissions & Incentive Databases
State-level regulatory bodies and incentive databases used for location-specific calculator adjustments. DSIRE is the canonical national database; individual state PUC sites are used for net metering rules and utility-specific rate verification.
- DSIRE— Database of State Incentives for Renewables & Efficiency
- Comprehensive database of state, local, utility, and federal incentive programs
- Arizona (ACC)— Arizona Corporation Commission
- Arizona utility regulation & net metering rules
- California (CPUC)— California Public Utilities Commission
- California utility regulation, NEM 3.0 tariffs & solar incentives
- Colorado (PUC)— Colorado Public Utilities Commission
- Colorado utility regulation & net metering policy
- Connecticut (PURA)— Connecticut Public Utilities Regulatory Authority
- Connecticut utility regulation & solar incentive programs
- Florida (PSC)— Florida Public Service Commission
- Florida utility regulation & net metering rules
- Georgia (PSC)— Georgia Public Service Commission
- Georgia utility regulation & distributed generation / avoided-cost NEM rules
- Hawaii (PUC)— Hawaii Public Utilities Commission
- Hawaii utility regulation & solar tariff programs (Customer Self-Supply, Grid-Supply)
- Illinois (ICC)— Illinois Commerce Commission
- Illinois utility regulation & Smart Solar Billing Program / Illinois Shines net metering rules
- Maine (PUC)— Maine Public Utilities Commission
- Maine utility regulation & Net Energy Billing (NEB) program rules
- Maryland (PSC)— Maryland Public Service Commission
- Maryland utility regulation & net metering / SREC programs
- Massachusetts (DPU)— Massachusetts Department of Public Utilities
- Massachusetts utility regulation & SMART solar incentive program
- Michigan (PSC)— Michigan Public Service Commission
- Michigan utility regulation & Distributed Generation Program (DGP) net metering rules
- Minnesota (PUC)— Minnesota Public Utilities Commission
- Minnesota utility regulation & Solar*Rewards / net metering policy
- Missouri (PSC)— Missouri Public Service Commission
- Missouri utility regulation & NEM 1.0 retail-rate net metering regulation
- Nevada (PUC)— Nevada Public Utilities Commission
- Nevada utility regulation & net metering tariff
- New Jersey (BPU)— New Jersey Board of Public Utilities
- New Jersey utility regulation & TREC / SuSI solar incentive programs
- New Mexico (PRC)— New Mexico Public Regulation Commission
- New Mexico utility regulation & 1:1 net metering / 10% state solar tax credit program
- New York (PSC)— New York Public Service Commission
- New York utility regulation & NY-Sun / Value of Distributed Energy Resources (VDER) tariff
- North Carolina (NCUC)— North Carolina Utilities Commission
- North Carolina utility regulation & HB 589 net metering / 80% property tax exemption rules
- Ohio (PUCO)— Ohio Public Utilities Commission
- Ohio utility regulation & uniform retail-rate net metering under Ohio Rev. Code § 4928.67
- Oregon (PUC)— Oregon Public Utility Commission
- Oregon utility regulation & net metering rules
- Pennsylvania (PUC)— Pennsylvania Public Utility Commission
- Pennsylvania utility regulation & net metering / SREC-II program rules
- Rhode Island (PUC)— Rhode Island Public Utilities Commission
- Rhode Island utility regulation & Renewable Energy Growth (REG) / net metering rules
- South Carolina (PSC)— South Carolina Public Service Commission
- South Carolina utility regulation & Solar Choice Tariff (Act 62) / net metering rules
- Texas (PUC)— Public Utility Commission of Texas
- Texas utility regulation & distributed generation interconnection rules (deregulated market)
- Utah (PSC)— Utah Public Service Commission
- Utah utility regulation & Net Billing (2025 transition from NEM) program rules
- Vermont (PUC)— Vermont Public Utility Commission
- Vermont utility regulation & Group Net Metering (Rule 5.100) / net metering policy
- Virginia (SCC)— Virginia State Corporation Commission
- Virginia utility regulation & net metering / VCEA clean energy programs
- Washington (UTC)— Washington Utilities and Transportation Commission
- Washington utility regulation & net metering rules
- Wisconsin (PSC)— Wisconsin Public Service Commission
- Wisconsin utility regulation & utility-specific net metering rates (per-IOU tariffs for 5 major IOUs)
Industry Standards & Research
Industry bodies and research organizations that provide cost benchmarks, efficiency ratings, and market data.
- Edmunds— Edmunds (EV TCO)
- Electric vehicle true cost of ownership benchmarks & depreciation data
- ENERGY STAR— EPA ENERGY STAR Program
- Appliance & HVAC efficiency ratings used in upgrade calculators
- SEIA— Solar Energy Industries Association
- U.S. solar market data, installation cost benchmarks & industry statistics
- Wood Mackenzie— Wood Mackenzie (Formerly GTM Research)
- Solar and energy storage market reports used for cost trend calibration
Data Providers & Per-Calculator Formulas
Infrastructure data providers and calculator-specific formula sources. For each calculator, the exact formula, assumptions, and primary sources are documented on the Methodology page.
- SimpleMaps— SimpleMaps US ZIP Code Database
- U.S. ZIP code–to–latitude/longitude mapping for location-aware calculations
Top Calculator Formula Sources
Seven calculators with the most specialized data pipelines. All other calculators reference federal agency APIs listed above — see individual calculator methodology sections for source-specific citations.
Solar ROI Calculator
NREL System Advisor Model (SAM) + IRS Form 5695 (Residential Clean Energy Credit) — source
Solar Panels Needed Calculator
NREL PVWatts API (location-specific production estimates) — source
EV Total Cost of Ownership
Edmunds TCO methodology + EIA state electricity rates — source
EV Charging Cost Calculator
EIA state electricity rate API + DOE EVSE efficiency specs — source
Heat Pump Savings Calculator
ENERGY STAR HSPF/SEER ratings + EIA state energy rates — source
Insulation ROI Calculator
DOE ZIP-2 insulation R-value recommendations + EIA heating fuel rates — source
Solar Loan vs Cash Calculator
IRS Form 5695 credit structure + NREL PVWatts system production — source
Questions about a specific data source or formula? See our About page for our independence policy, Methodology for per-calculator formula details, or browse Solar calculators to see these sources in action.