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24V Solar Calculator

Size a complete 24V solar system. Enter your daily loads and battery bank — get panels, charge controller, inverter, and a comparison to 12V wiring losses.

24V system loads
Wh/day
Ah
hrs/day
24V solar system specification
1 panels (400W total)
Daily production1,700 Wh/day
Battery usable capacity3.8 kWh
Days of autonomy2.6 days
Charge controller size21A MPPT (24V)
Inverter size0.5 kW (24V input)
24V vs 12V wire efficiency~75% less wiring loss
24V system advantages: Half the current of 12V = thinner wire, less voltage drop, higher efficiency. Ideal for systems above 400W. Most pure sine inverters work well at 24V.
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How to Use This Calculator

Enter your daily energy use (Wh/day), 24V battery bank capacity (Ah), battery type, and peak sun hours. The calculator outputs the complete 24V system specification: panels, battery usable capacity, days of autonomy, charge controller size, and inverter size — plus a comparison to equivalent 12V wiring losses.

When to choose 24V over 12V

A 24V system makes sense when your daily energy use exceeds about 400Wh or your solar array is larger than 400W. At 24V, current is halved compared to 12V for the same power, which means you can use thinner, cheaper wire and experience far less resistive heat loss. Most RV, van, and cabin systems above 400W are better served by 24V.

Building a 24V battery bank

Connect two 12V batteries in series (+ to -) to create 24V. The Ah capacity remains the same as a single battery. To increase Ah at 24V, connect identical series pairs in parallel. Example: two pairs of 100Ah 12V batteries = 24V 200Ah (4.8 kWh total).

24V vs 12V System Comparison

Same power, half the current3,000W at 24V = 125A vs 250A at 12V
Wire size savings12V needs 2/0 AWG; 24V needs only 4 AWG
Heat loss reduction75% less resistive loss (I²R — current squared × resistance)
Inverter efficiency24V inverters typically 1-2% more efficient
Charge controller costLower amperage rating needed at 24V

FAQ

For RVs using under 400Wh/day (a weekend warrior), 12V is fine and simpler. For full-time RVers or anyone with significant loads (refrigerator, air conditioning, power tools), 24V is strongly recommended. At 24V you need thinner cables, a smaller (and cheaper) MPPT controller, and experience less voltage drop over long wire runs in a large vehicle. Most professional van conversions above 400W use 24V or 48V systems.
Two options: (1) Use 12V nominal panels wired in series pairs — two 12V panels in series = 24V string input; or (2) Use 24V nominal panels directly. With an MPPT controller, you're not limited to matching panel voltage to battery voltage — the MPPT controller's input accepts a wide voltage range (typically 12-150V) and outputs the correct charging voltage. Wire panels in series to reduce current and simplify connections.
Yes, with a DC-DC converter (buck converter) that steps 24V down to 12V for 12V loads. Alternatively, run 12V loads from a 12V-to-120V inverter and power the 12V device from the AC outlet. For major loads like a 12V refrigerator, a good quality DC-DC converter is the cleanest solution. Never connect a 12V device directly to a 24V system — it will be immediately destroyed.

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