24V Battery Bank Calculator

Size an off-grid battery bank in amp-hours and kWh, with the batteries and solar array to match.

Your stateLoads the state's average price per watt, electricity price and solar output. You can edit any of them.

Daily use

kWh

Days without sun

days

System voltage

Depth of dischargeLithium iron phosphate often 80–100%; lead-acid 50%.

More settings

Inverter and battery efficiency

Battery voltage

Battery capacity

Yearly output per kWFrom NREL PVWatts for your state.

kWh/kW

Your result

Enter your numbers and press the button. Your result appears here.

At 24 V, every kWh of storage is 41.7 Ah. 24 V suits mid-size cabins and RVs.

Ah = daily kWh × days × 1,000 ÷ (volts × depth of discharge × efficiency). Batteries in series = system volts ÷ battery volts.

Example: 5 kWh a day for 2 days at 24 V and 80% depth of discharge needs 579 Ah (13.9 kWh).

Same settings as the calculator, changing only the daily use.

Daily use	Bank	Nominal	Solar array
2 kWh	231 Ah at 24 V	5.6 kWh	0.53 kW
3 kWh	347 Ah at 24 V	8.3 kWh	0.80 kW
5 kWh	579 Ah at 24 V	13.9 kWh	1.34 kW
8 kWh	926 Ah at 24 V	22.2 kWh	2.14 kW
10 kWh	1,157 Ah at 24 V	27.8 kWh	2.67 kW

What voltage should an off-grid system use?

12 V for small loads, 24 V for mid-size systems and 48 V for whole homes. Higher voltage means lower current and thinner cables.

How many days of storage do I need?

Two to three days is common where cloudy spells are short. A backup generator lets you use fewer.

NREL PVWatts v8 (20° tilt, south-facing, 14% losses), state results compiled by TheGreenWatt: https://thegreenwatt.com/average-peak-sun-hours-by-state/