Methodology and sources

• Every price, fee, and rebate links to a public source and shows the date we checked it.
• Sources are labeled by type: installer, utility, permit office, or user report.
• We never estimate a number a source does not publish; we say "not published" instead.
• Installer-published prices are marketing figures; we show at least two sources where we can.
• Rebates change often; we re-check each city page on a regular schedule and update the "last reviewed" date.