Off-grid solar sizing starts with honest daily load and realistic sun—not sticker panel watts alone. This guide walks through the RV solar and house battery calculator so you see whether rooftop harvest covers fridge, lights, and inverter draws before you buy more hardware.
Benefits
- Daily yield Wh = panel W × peak sun h × system efficiency—compared directly to daily load Wh.
- Shows bank Ah headroom when harvest falls short of house consumption at your bus voltage.
- Pairs with solar panel size and battery bank tools for full off-grid and boondocking planning.
How it works
- Enter installed or planned panel watts, site peak sun hours, and system efficiency (typical 75–85%).
- Add total daily house load in Wh/day—fridge, lights, pumps, inverter loads.
- Set house voltage (12 V or 24 V); review daily solar yield vs. load and any Ah bank shortfall.
FAQ
How do I size an off-grid solar system for an RV?
Compare daily harvest to daily use. Harvest ≈ panel W × sun h × efficiency. Example: 400 W × 5 h × 0.80 = 1,600 Wh/day. If load is 1,800 Wh/day, you are 200 Wh short—about 17 Ah extra bank at 12 V before overnight margin. Increase panels, cut load, or add storage.
What daily Wh should I use for RV house loads?
Sum appliance Wh/day: fridge often 400–800 Wh, LED lighting 50–150 Wh, water pump and fans 100–300 Wh, inverter loads as needed. A smart-plug audit beats guessing—enter the total in the calculator.
Should I use summer or winter sun hours for sizing?
Use winter or shoulder-season sun hours for conservative off-grid sizing—especially if you boondock year-round. Summer surplus does not help on a cloudy November week unless you size storage for those gaps.
Technical specifications
- Daily yield Wh = panel_W × peak_sun_h × (efficiency ÷ 100).
- Shortfall Wh = load Wh − yield Wh when yield < load.
- Bank Ah headroom ≈ shortfall Wh ÷ house voltage.
- Related: solar-panel-size, solar-battery-bank, solar-roof-space.
Harvest must beat the house load
Rooftop space is finite—every panel should earn its keep against real Wh/day, not brochure STC ratings. The calculator compares what your array harvests in peak-sun-equivalent hours against what the house draws. A shortfall shows up as Ah you must carry in the bank until the next sunny day.
Efficiency is not optional
Wiring, controller, temperature, and partial shade eat harvest. An 80% system efficiency factor on 400 W panels is more honest than assuming nameplate output all afternoon. Size with that margin before you commit to lithium upgrades or a second roof rack.