Battery banks for off-grid homes are sized for daily use times the days you want to ride through without sun.
How it works
Ah = daily kWh × days × 1,000 ÷ (volts × depth of discharge × efficiency). Batteries in series = system volts ÷ battery volts.
Example: 10 kWh a day for 2 days at 48 V and 80% depth of discharge needs 579 Ah (27.8 kWh).
At a glance
Same settings as the calculator, changing only the daily use.
| Daily use | Bank | Nominal | Solar array |
|---|---|---|---|
| 2 kWh | 116 Ah at 48 V | 5.6 kWh | 0.53 kW |
| 5 kWh | 289 Ah at 48 V | 13.9 kWh | 1.34 kW |
| 10 kWh | 579 Ah at 48 V | 27.8 kWh | 2.67 kW |
| 15 kWh | 868 Ah at 48 V | 41.7 kWh | 4.01 kW |
| 20 kWh | 1,157 Ah at 48 V | 55.6 kWh | 5.34 kW |
| 30 kWh | 1,736 Ah at 48 V | 83.3 kWh | 8.01 kW |
Common questions
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.
Sources
- NREL PVWatts v8 (20° tilt, south-facing, 14% losses), state results compiled by TheGreenWatt: https://thegreenwatt.com/average-peak-sun-hours-by-state/