Monthly electricity use can take you straight to Panel Count. The same assumptions then carry into Savings and Battery Sizing, so you do not restart from zero later.
Planning estimate only. Use it to compare options before you make a purchase decision.
Compare panels required by usage with the maximum that fits your roof
Try Now →Estimate your solar payback period by state
Try Now →Size your home battery for backup power
Try Now →Carbon impact remains available after the main sizing, savings, and battery path.
Open Carbon Calculator →Pick one worked example, edit the inputs, copy the result summary, and challenge the assumptions if they do not match your case.
One calculation state. Country, monthly use, electricity rate, sun-hours, panel wattage, losses, and roof area carry through Panel Count, Savings, and Battery Sizing. You can edit them at every step.
Visible boundaries. Each result shows its formula basis, assumptions, and limitations. PVSize does not promise installer quotes, installation outcomes, or engineering approval.
Assumptions: Country defaults are starting points, not claims about a specific roof or utility tariff.
Data source: Public rate references, PVWatts-style solar-yield assumptions, and user-selected inputs.
Last reviewed: July 18, 2026.