Company
About WattMath
Our mission, methodology, and the team behind the calculators.
"Homeowners deserve accurate answers — not answers based on a tax law that changed a year ago."
The reason WattMath exists
WattMath is a free suite of residential energy calculators for homeowners making major energy decisions — solar panels, electric vehicles, heat pumps, EV charging, and home battery backup.
Who operates WattMath
WattMath is operated by BP Technology Advisors LLC, a technology consulting firm based in Tennessee. We built WattMath because most energy calculators available to homeowners were built before July 2025 — when the One Big Beautiful Bill Act (Public Law 119-21) significantly changed the federal tax credit landscape for solar, EVs, and heat pumps. Most incumbent tools were still showing the 30% solar ITC, the $7,500 EV credit, and the $2,000 heat pump credit as available in 2026. They are not.
WattMath uses post-OBBBA numbers sourced directly from the IRS, NREL, and EIA. Homeowners deserve accurate answers, not answers based on a law that was changed a year ago.
Why trust WattMath
NREL PVWatts
Government-grade solar data
Solar production estimates use the same model utilities and professional installers rely on nationwide.
EIA Open Data
Real rates, refreshed monthly
Electricity and gas prices come from the U.S. Energy Information Administration — not marketing estimates.
Open Methodology
Every formula documented
Each calculator publishes its formulas, assumptions, and data refresh dates. No black-box answers for a $30K decision.
How we build our calculators
Every calculator on WattMath uses authoritative primary data sources:
- Solar production — NREL PVWatts API, the same tool used by installers, utilities, and the U.S. Department of Energy.
- Electricity rates — U.S. Energy Information Administration (EIA) monthly residential data, cached and refreshed automatically.
- Federal tax credits — IRS publications and the OBBBA FAQ, reflecting Public Law 119-21 (signed July 4, 2025). Solar 25D and air-source heat pump 25C credits expired December 31, 2025; geothermal 25D and home charger 30C credits shown where still active.
- State and local incentives — hand-verified quarterly from DSIRE and utility program pages, with last-verified dates shown in results.
We publish our methodology for each calculator so you can check our math. We never determine tax credit eligibility for individual users — that requires a tax professional. We show what credits exist, what the rules are, and where to get authoritative guidance.
How we make money
WattMath earns revenue through two clearly-disclosed sources:
- Display advertising — programmatic ads served through standard ad networks. These are labeled and separate from calculator content.
- Affiliate partnerships — WattMath earns a referral fee from Amazon (EV charging hardware) and similar partners. These are disclosed on every page where they appear. We do not sell leads to solar installers or other vendors directly.
We do not have a financial stake in any energy product category. Our affiliate disclosures are on every page where they appear — never hidden.
Our methodology principles
- Primary government data only: NREL, EIA, IRS. We do not use vendor data for core calculations.
- Formulas published on every calculator's methodology page — no black-box answers.
- Data currency dates shown in results — you always know how fresh the numbers are.
- Tax law changes applied promptly. OBBBA went into effect July 4, 2025; our calculators reflected the new rules within weeks.
Get in touch
Found an error in our math? Have a calculator suggestion or data correction?