How to Calculate the Right Energy Storage System Size for Your Home

When choosing a home energy storage system, one of the most common questions is:

“How big should my battery be?”

Getting this right is essential — too small, and you’ll run out of power; too large, and you’ll overspend. Let’s walk through a simple method used by professionals to estimate the ideal LiFePO4 battery capacity for your solar energy system.

The Basic Formula

To find the right battery capacity, you can use this simple formula

Where:

Pᵢ = Power of each appliance (in kW)

Tᵢ = Operating time (in hours)

Inverter Efficiency = Typically around 90% (0.9)

DOD (Depth of Discharge) = Usually 80% (0.8) for LiFePO4 batteries

Example Calculation

Let’s take a look at a typical household setup:

Recommended Battery System: ~10 kWh

So, 10 kWh LiFePO4 battery would be ideal for this home’s daily energy use — providing reliable power backup even during cloudy days or grid outages.

Real-World Example: SUNESS  10.24kWh LiFePO4 Battery

SUNESS offers EV-10.24N LiFePO4 battery (10.24kWh) designed specifically for home and commercial use.

Here’s why it’s the perfect match:

High Efficiency: Over 95% usable energy with 90% inverter compatibility

Long Lifespan: 8,000+ charge/discharge cycles and a 10-year warranty

Smart Management: Built-in BMS with CAN/RS485 for real-time monitoring

 Flexible Installation: Rack or wall mount, easy to expand up to 16 units

With a SUNESS battery, you can store solar power during the day and use it at night — saving energy costs while enjoying 24/7 power stability.

Quick Tip for Homeowners

Think of your solar battery like a water tank —

Your solar panels are the faucet (charging energy).

Your appliances are the outlets (using energy).

The larger your tank (battery), the more energy you can store for later.

Choosing the right capacity ensures your “tank” never runs dry when you need it most.