How do I size a solar battery bank for off-grid use?

Multiply the daily energy by the autonomy days, divide by the inverter efficiency, then divide by the depth of discharge and temperature derating.

What depth of discharge should I use for LiFePO4?

LiFePO4 banks are typically sized to 80–90% depth of discharge, while lead-acid banks are limited to about 50% to protect cycle life.

How is the battery cable and fuse size chosen?

The maximum continuous current is multiplied by a 1.25 safety factor, then matched to a copper conductor ampacity and a Class-T fuse per NEC 310.16 and NEC 240.6.

Command Center

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Solar Battery Bank Sizer

Size a battery bank, array, and inverter for off-grid and hybrid solar installations.

Daily Load

Daily energy demand

Bank Configuration

Bus voltage

Chemistry

Autonomy days

days

Temperature derating

Inverter efficiency

Continuous load

Battery module

Computed Readouts

24V · LIFEPO4

Required energy: 6,666.67 kWh
Total bank energy: 7,058.82 kWh
Bank capacity: 294 Ah
Series × parallel: 2S × 2P
Total modules: 4
Installed energy: 9,600.00 kWh
Max continuous amps: 93.8 A
NEC cable size: 2 AWG
Class-T fuse: 100 A

Live Wiring Diagram

Hardware BOM

7 lines · 10 units

Item	Specification	Qty
Battery module — 12V 200Ah2S2P	LiFePO4 · 12V · 200Ah	4 units
Class-T fuseNEC 690.7	100A · 125Vdc interrupt	1 ea
Class-T fuse holder	Rated 100A · 24Vdc	1 ea
Battery interconnect cableNEC 310.16	2 AWG copper · 75°C	1 set
MPPT charge controller	24V nominal · 94A min	1 ea
Inverter / charger	24Vdc input · 2000W continuous	1 ea
Busbar set	Rated 100A · 24Vdc	1 set

Worked Formula

Step 1E_req = (E_daily × days) ÷ η_invE_req = (3,000 Wh × 2) ÷ 0.90E_req = 6,667 Wh
Step 2E_bank = (E_req ÷ DoD) × k_tempE_bank = (6,667 ÷ 0.85) × 0.90E_bank = 7,059 Wh
Step 3Ah_bank = E_bank ÷ V_sysAh_bank = 7,059 ÷ 24Ah_bank = 294 Ah
Step 4I_max = (P_cont ÷ V_sys) × η_inv × 1.25I_max = (2,000 ÷ 24) × 0.90 × 1.25I_max = 93.8 A

Solar Battery Bank Sizer Presets

12 presets