Panel watts and battery amp-hours both answer to the same daily Wh budget. Build an honest load list first—fridge cycles, inverter draws, lighting—then see whether your panels refill the bank and how much Ah headroom you need when the sky turns gray.
Benefits
- Links daily load Wh to minimum panel watts via sun hours and system efficiency.
- Translates harvest shortfall into Ah bank headroom at 12 V or 24 V house voltage.
- Helps compare adding panels vs. deepening the house bank when boondocking margins are thin.
How it works
- Total daily off-grid Wh from appliance audit (fridge, HVAC fan, pumps, electronics).
- Run panel W, sun hours, and efficiency to get daily solar yield Wh.
- If yield < load, read Ah bank headroom; increase panels, load, or voltage inputs to test upgrades.
FAQ
How do I calculate solar panel capacity for off-grid RV loads?
Minimum panel W ≈ daily Wh ÷ (peak sun h × efficiency). Example: 2,000 Wh/day ÷ (4.5 h × 0.80) ≈ 556 W rooftop. Cross-check in the RV calculator: enter that array and your load—yield should meet or exceed Wh/day.
How do I calculate battery capacity for off-grid loads?
When solar yield falls short, shortfall Wh ÷ house voltage ≈ Ah drawn from the bank that day. For multi-day autonomy, multiply daily shortfall (or full daily load on zero-sun days) by backup days and divide by usable DoD. The tool surfaces Ah headroom for a single-day gap.
Panels first or batteries first?
Fix the daily Wh balance first—panels that cover load reduce how hard you cycle the bank. If yield already exceeds load but you still run out overnight, deepen Ah storage. If yield trails load every day, more panel watts (or less consumption) comes before a bigger bank.
Technical specifications
- Panel W (min) ≈ daily load Wh ÷ (peak sun h × efficiency fraction).
- Daily yield Wh = panel W × sun h × efficiency.
- Bank Ah shortfall ≈ (load Wh − yield Wh) ÷ house voltage when yield < load.
- Related: solar-battery-bank, battery-bank-size, fridge-energy-usage.
One daily Wh ledger
Off-grid design fails when loads live in separate spreadsheets. Fridge, inverter, and lighting Wh belong in one daily total—the same number you enter as house load. Panel and bank sizing both read from that ledger; changing one appliance changes both answers.
Panels harvest; batteries bridge
Panel capacity answers how fast you refill during sun hours. Bank Ah answers what happens when harvest stops at dusk—or for the second cloudy day. The RV calculator shows the gap between yield and load in Wh and Ah so you know which side of the system to grow.