Most RV and marine house systems run at 12 V or 24 V. The same daily Wh shortfall is half the amps at 24 V as at 12 V—enter your house voltage, panel watts, sun hours, and load to see whether your low-voltage stack keeps up.
Benefits
- Models 12 V and 24 V house buses with the same Wh yield vs. load math.
- Converts energy gaps to Ah—lower current and smaller cables at 24 V for the same Wh.
- Built for camper fridges, LED lighting, and inverter loads on standard RV voltages.
How it works
- Choose house voltage—12 V is common on older campers; 24 V on many coaches and builds.
- Enter panel watts, peak sun hours, efficiency %, and daily house load Wh.
- Compare daily yield to load; read surplus Wh or Ah bank headroom at your bus voltage.
FAQ
How do I estimate a 12V RV solar power system?
Daily yield ≈ panel W × sun h × efficiency. Example: 300 W × 5 h × 0.80 = 1,200 Wh/day. At 1,500 Wh load, shortfall is 300 Wh—25 Ah at 12 V. Add panels, cut load, or carry 25+ Ah usable headroom in the house bank.
Is 24V better than 12V for RV solar?
Same Wh need either way—24 V halves amperage for identical power, which helps on long wire runs and heavy inverter loads. Many OEM RVs stay 12 V; coach and DIY builds often choose 24 V. This calculator accepts either house voltage input.
How does daily Wh relate to my 12V or 24V Ah rating?
Ah ≈ Wh ÷ voltage. A 400 Wh daily shortfall is about 33 Ah at 12 V or 17 Ah at 24 V. Nameplate bank Ah must exceed that after depth-of-discharge limits—lithium and lead-acid usable Ah differ.
Technical specifications
- Daily yield Wh = panel_W × peak_sun_h × (efficiency ÷ 100).
- Shortfall Ah ≈ (load Wh − yield Wh) ÷ house voltage (12 or 24).
- Surplus Wh = yield Wh − load Wh when panels exceed consumption.
- Related: battery-bank-size, inverter-sizing, camping-fridge-runtime.
Voltage changes amps, not energy
A 1,800 Wh daily load is the same whether the bus is 12 V or 24 V—the amp-hour draw on the bank differs. Enter the voltage your coach actually runs so shortfall Ah matches your monitor and shunt readings.
12 V familiarity vs. 24 V efficiency
12 V components dominate the RV aftermarket—controllers, fuses, and appliances are easy to find. 24 V reduces current for the same wattage, which matters when the inverter runs microwave or AC loads. Either way, panel yield must cover daily Wh before voltage choice saves you.