Terms of use

Use the calculators freely. They produce planning estimates from published data and stated assumptions, and by using them you accept that they are exactly that.

Estimates, not designs

PanelTally provides sizing estimates for information and planning. It is not an engineering design, not a production guarantee, and not a substitute for a site survey, a PVWatts run on your address, or an installer's load analysis. Statewide sun averages hide local variation; roofs differ; assumptions are stated and yours may not match them. When our number and a professional's disagree, the professional looking at your actual roof wins.

Not financial or tax advice

Nothing on this site estimates or advises on system cost, payback, financing, incentives, or taxes. Panel counts are hardware arithmetic, and we keep it that way deliberately. Decisions about spending money on solar belong with your own judgment and, where it matters, a professional advisor.

The usual paragraph

Content is provided as-is without warranties of any kind; to the maximum extent permitted by law we are not liable for damages arising from use of this site. Outbound links don't imply endorsement. These terms can change with the site, and the effective date below tracks the current revision. If part of this page is unenforceable where you live, the rest still applies.

Effective 2026-07-15. Questions: contact.