Sources, methodology & editorial policy
How we choose sources, date our numbers, label estimates, fix mistakes, and keep money out of our results.
Where our numbers come from
- Primary sources first: manufacturer spec sheets and pricing pages, federal agencies (IRS, EIA, Ready.gov, CDC, CPSC, FDA, DOE), state energy offices, NASEO, and utilities.
- Established cost surveys such as EnergySage for installed battery and solar prices. When a number comes from a comparison site or contractor rather than the primary source, we say so.
- The full source list and every calculator assumption are on the About page.
Editorial rules
- Every figure links to its source and carries an "as of" date.
- Estimates and assumptions are labeled Estimate.
- We do not publish invented statistics, reviews, testimonials, or activity counters. If we cannot verify a number, we leave it out and say so.
- Safety guidance follows official agencies (Ready.gov, CDC, CPSC) and we always point readers to a licensed electrician for anything wired into a home.
- We write in plain, calm language. No scare tactics.
Updates and corrections
Each guide shows a "Last updated" date. Prices and program status change, so we re-check sources and update the date when we do. If you find an error, tell us; confirmed corrections are made on the page and the date is updated.
Money and independence
We may earn a commission from some product links or installer quote requests. That never changes a number or a ranking: calculator matches are sorted by fit and then price. See the affiliate disclosure.