SolarPanelCostGuide started as a single spreadsheet for checking whether a solar quote made sense. It grew into four calculators that do the same math in the browser: system cost after the 30% federal credit, payback period, system size, and the credit itself split out from installation and battery cost.
Every calculator runs on your device. Type in a number and the arithmetic happens in JavaScript right there; nothing gets logged or sent to a server. That also means the tools can't look up your address, your roof pitch, or your utility's actual rate. They only know what you type in.
The guides and calculators here are written and maintained by Jessica Martinez. See how figures get sourced and checked on the editorial standards page, or read more about who writes here on the authors page.
Nothing on this site is an installer quote or a tax return. Get real numbers from a licensed installer and confirm credit eligibility with a tax preparer before you commit to anything.