Battery Sizing Calculator

Size an off-grid or backup battery bank from your loads, autonomy days, chemistry & depth-of-discharge. Get series/parallel counts for common modules.

Critical Loads

Add load (Watts)

Hours per day

Label (optional)

Label	Watts	Hours/day	Wh/day
Total			0

Assumptions

Days of autonomy

Days you want to run without charging

System DC voltage

Higher V = lower current, smaller cables

Chemistry preset

Sets default DoD & efficiency

Depth of discharge (DoD %)

Usable fraction of nominal capacity

Round-trip efficiency (%)

Battery + wiring + converter losses

Inverter efficiency (%)

AC conversion losses

Safety margin (%)

Extra headroom for aging & weather

Peak sun hours (for recharge)

Used to estimate PV kW to recharge in 1 day

Estimate peak power (W)

Or leave blank to sum all Watts

Results

Daily energy (kWh)

—

Required usable capacity (kWh)

—

Energy delivered to loads over autonomy window

Required nominal capacity (kWh)

—

Accounts for DoD limit & margin

Bank size at 48 V (Ah)

—

Ah = nominal kWh × 1000 / system volts

Est. inverter continuous (W)

—

PV to recharge in 1 day (kW)

—

Approx. usable kWh ÷ PSH

Suggested Battery Configurations

Counts are rounded up. Real designs consider vendor specs, BMS limits, and code requirements.

Save / Share

The link encodes your loads and all inputs. Share it to recreate this exact setup.