About this calculator
A neutral, no-signup tool for sizing off-grid and backup solar systems — built because most online sizing calculators exist to route you toward a particular retailer's products.
Retailer calculators are useful, but they are sales funnels: they nudge you toward their own batteries and panels, often require an email, and rarely size the whole system end to end. This tool does the opposite. It is brand-agnostic, stores nothing, asks for nothing, and walks the full chain — load, battery bank, solar array, charge controller and inverter — so you leave with a complete picture you can price out anywhere.
The chemistry constants and formulas are documented on the methodology page. If you find an error, the contact link is below — corrections are welcome.
Built and maintained by Murugan Vellaichamy, a software engineer who builds independent web tools.