All Tools
Every solar calculator.
Free, no sign-up, every formula shown. Pick the tool that matches your setup: RV, off-grid cabin, home rooftop, battery bank, payback math, or EV charging.
RV Solar Sizing
Size your panel array, battery bank, and charge controller for van life or RV travel.
↳ 500 Wh/day, 5 sun hrs → 125W panels
Off-Grid Cabin System
Full off-grid system design: panels, batteries, inverter size, and estimated cost range.
↳ 3 kWh/day, 3 days backup → 750W array, ~11 kWh bank
Home Solar Savings
Annual savings, payback period, and 25-year ROI using your state's sun hours and utility rates.
↳ $180/mo bill in CA → ~5 yr payback
Battery Bank Sizing
Size a battery bank for backup or off-grid use: DoD, voltage, chemistry, and string layout.
↳ 5 kWh/day, 3 days, 48V → 20 × 100Ah
Solar Payback & ROI
Simple payback, IRR, NPV, and a 25-year savings chart, with rebates and cash, loan, or lease financing.
↳ 6 kW, $16.5K in CA → ~5 yr payback
Solar + EV Planner
Extra panels needed to cover EV charging, fuel savings vs. gas, and annual charging cost.
↳ 200 mi/wk → +6 × 400W panels