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

Calculate your daily energy consumption in kWh, multiply by days of autonomy, divide by depth of discharge (0.5 for lead-acid, 0.8 for LiFePO4), then divide by system voltage to get Ah. This calculator handles the entire process step by step.

What is the difference between lead-acid and LiFePO4 batteries?

LiFePO4 batteries have higher usable capacity (80% DoD vs 50% for lead-acid), longer lifespan, and require no maintenance. Lead-acid is cheaper upfront but needs larger banks for the same usable energy and requires ventilation.

How many solar panels do I need to charge my battery bank?

Divide your daily energy consumption by (peak sun hours x system efficiency). For example, 5000 Wh/day / (5 hrs x 0.85) = 1176W of panels. The charge controller should be sized at 125% of panel short-circuit current.

Battery Bank Calculator

Size batteries for off-grid and backup solar systems. Step-by-step wizard to calculate kWh, Ah, solar panels, and charge controller requirements.

Step 1: Add Appliances

System Voltage

Battery Type

Days of Autonomy

Peak Sun Hours

Battery Voltage (per battery)

Battery Capacity (Ah)

How to Size Your Battery Bank

Three simple steps to design your solar storage system.

Add Appliances

Select or enter appliances with wattage and daily usage hours. Choose from common presets like lights, fridge, TV, and more.

Configure System

Choose system voltage (12/24/48V), battery type (Lead-acid or LiFePO4), days of autonomy, and peak sun hours for your location.

Review Design

Get complete system specifications: battery bank size, series/parallel configuration, solar panel wattage, and charge controller rating.

Frequently Asked Questions

Common questions about battery bank sizing for solar systems.

Calculate daily energy consumption, multiply by days of autonomy, divide by depth of discharge, then divide by system voltage. For example: 5000 Wh/day x 3 days / 0.8 DoD / 24V = 781 Ah at 24V.

LiFePO4 batteries offer 80% usable capacity vs 50% for lead-acid, last 3-5x longer, weigh less, and require no maintenance. Lead-acid is cheaper initially but needs larger banks for the same usable energy.

Series increases voltage (e.g., 2 x 12V = 24V) while keeping Ah the same. Parallel increases Ah (e.g., 2 x 100Ah = 200Ah) while keeping voltage the same. Most systems use a combination to achieve both target voltage and capacity.