RV solar recharge calculator — panel watts, sun and daily loads
Plan daily off-grid energy balance with realistic editable solar derating and consumption estimates.
Solar recharge estimator
A panel's watt rating is not daily watt-hours. Use equivalent full-sun hours and a loss factor to estimate how much energy reaches the battery under your assumptions.
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Your estimate
Weather, shade, charge-stage tapering, battery voltage and controller behavior vary. This is an energy-budget estimate only, not electrical system sizing or a charge-safety recommendation.
How much solar is enough for the daily load?
At an assumed four equivalent peak-sun hours and 75% net yield, a 400Wh daily battery-side demand needs 400 ÷ (4 × 0.75) = about 134W of panel nameplate just to break even. A 200W example array yields 600Wh/day, leaving 200Wh/day to restore storage. Replacing an additional 800Wh then takes four modeled days, not 800 ÷ 600 days, because the ongoing load still consumes energy.
Compare good and poor sun before adding panels
Keep the 200W array, 75% yield and 400Wh/day demand fixed. The table varies only equivalent peak-sun hours. These are scenarios, not a forecast for your parking spot.
| Peak-sun hours | Wh/day produced | Net Wh/day | Restore 800Wh |
|---|---|---|---|
| 5 | 750 | +350 | 2.3 days |
| 4 | 600 | +200 | 4 days |
| 2 | 300 | −100 | No recovery |
| 1 | 150 | −250 | No recovery |
What does the 75% factor include?
Here it is your combined panel-to-battery energy assumption: allow for your installation's shade, orientation, heat, controller and wiring losses. It is not a manufacturer's universal efficiency rating. Peak-sun hours are the equivalent energy of full-rated sunlight, not hours from sunrise to sunset. Replace both assumptions with local seasonal irradiance and observed yield.
Use the same battery-side boundary for demand and replenishment. If your load figure is AC appliance energy, account for inverter losses before entering battery-side demand. The seven-day planner instead uses a solar-to-load yield factor and load-equivalent storage; those values must not be mixed with a battery-terminal meter reading without conversion.
Daily energy balance is only one constraint
A positive daily net does not prove that the battery survives the night or several cloudy days. Try the cloudy-first seven-day stress test and compare it with your minimum reserve. Actual recharge can take longer as charging tapers or equipment limits input. Check the controller or station's documented PV voltage, current and input limits before choosing panels; this calculator does not select a safe series/parallel arrangement.
Sources and calculation notes
Documentation checked 2026-10-24. Manufacturer specifications describe the named product or range, not every battery of that chemistry. Tables are our arithmetic under stated assumptions; they are not hands-on discharge tests or product recommendations.
What happens to your batteries during several cloudy days?
Build a seven-day reserve scenario from your own appliance loads, then save an equipment decision plan.
Turn your result into an equipment checklist
No fabricated product tests or affiliate claims. Compare verified specifications before buying.