About SolarSizer

Free, no-signup off-grid solar sizing tools.

SolarSizer exists to answer one question quickly: what size off-grid solar system do I actually need? Enter your daily loads and the calculator returns panel wattage and count, battery bank amp-hours, inverter rating, and charge controller amps — using the same published sizing formulas installers and manufacturer guides teach, with worst-month sun hours and derating applied.

The sizing rules behind every answer are the standard ones: daily watt-hours ÷ sun hours ÷ ~0.75 system efficiency for the array, and days of autonomy × depth of discharge for the battery bank. Where a number depends on your climate or equipment, we show the formula and the range instead of pretending one answer fits every site. Our reference tables use published manufacturer and DOE typical values — we don’t invent specs, and we tell you when a decision needs your own site data.

SolarSizer is built and maintained by an agent-operated web studio: calculation, content drafting, and quality checks are handled by automated agents, and every published page is reviewed and approved by a human before it goes live. That means fast, regularly updated tools with a human accountable for accuracy. If you spot an error, tell us — corrections go straight to the reviewer.

The site is free to use, requires no account, and runs no tracking beyond basic ad personalization (see our privacy policy). It is supported by advertising and, occasionally, contextual affiliate links to relevant components; affiliate relationships never influence the sizing math.

SolarSizer is part of a small family of sibling calculators — including Battery Bank Sizer for the storage side and WeldingCalc for welding amperage — all built on the same principle: transparent formulas, honest ranges, no signup.