When people shop for solar batteries, the first question is usually:
“Should I get 100Ah or 200Ah?”
But that’s the wrong place to start.
Battery size is not about Ah. It’s about how much energy your home or business consumes — and how long you want backup power to last.
Let’s break it down simply.
Step 1: Stop Looking at Ah. Look at kWh.
Amp-hour (Ah) alone does not tell you how big a battery is.
What matters is energy storage, measured in kilowatt-hours (kWh).
Formula:
Battery Energy (kWh) = Voltage (V) × Amp-hours (Ah) ÷ 1000
Example:
A 100Ah battery at 48V:
48 × 100 ÷ 1000 = 4.8kWh
Now compare that to:
A 200Ah battery at 24V:
24 × 200 ÷ 1000 = 4.8kWh
Same energy. Higher Ah does not automatically mean a bigger battery. You always want to do your calculations, so you know the total amount of energy in the battery
Step 2: Calculate Your Daily Usage
Before choosing a battery, you must know:
How many kilowatt-hours does your home use per day?
Simple example:
2 fridges → 1.5kWh per day
Lights + TV → 2kWh
WiFi + small electronics → 0.5kWh
Occasional ironing or microwave → 1kWh
Total ≈ 5kWh per day
If you install one 5kWh battery, you technically have one day of storage — in theory.
But real life is different for the reasons you will see below. As a result, ideally you want your battery bank to be at least 1.5x your total load.
Step 3: Understand Usable Capacity
Lithium batteries are not meant to be drained 100% daily.
Most 5kWh lithium batteries provide around 90–95% usable capacity.
So a 5kWh battery realistically gives about 4.5kWh usable energy.
If your home consumes 5kWh overnight, one battery may not be enough.
This is why we recommend that Infinity Solar helps you to size your load correctly.
Step 4: Decide What You Want the Battery To Do
Ask yourself:
• Do you want backup only for load shedding?
• Do you want to reduce ZESA dependence at night?
• Or do you want multiple days of autonomy?
These are very different goals.
Scenario A – Backup Only
If ZESA comes back daily, and you just want protection during outages, 5kWh–10kWh is usually enough for medium homes.
Scenario B – Reduced ZESA Dependence
If you want to rely mostly on solar and batteries at night, you may need 10kWh–20kWh depending on your load.
Scenario C – Off-Grid
If there’s no ZESA at all, battery sizing becomes much larger and more strategic.
You can also mix the different scenarios by switching off certain loads at night to save on the battery. The most common item people switch off at night is the fridge. However, it is always best to get the right battery size and not worry about switching loads off at night.
Step 5: Battery Size Balance With Your Inverter
Battery size must match your inverter and your load.
A 5kW inverter paired with a 5kWh battery works for moderate homes.
A 10kW inverter with only one 5kWh battery may drain the battery very quickly.
Think of it like this:
The inverter is how fast you can drink.
The battery is how much water is in the tank.
Big mouth, small tank = empty very quickly.
Power (kW) and storage (kWh) must be properly balanced.
How Infinity Solar Can Help
By implementing these simple 5 steps you can make sure you are getting the right battery for your needs.
At Infinity Solar, we stock batteries in different capacities to match different needs — from compact 5kWh home units to larger storage systems designed for bigger households and commercial setups.
Whether you need:
• A single battery for load shedding backup
• A multi-battery bank for reduced ZESA reliance
• Or a properly engineered system for business operations
We take time to calculate your load and recommend the right size — not just the biggest battery.
If you’re unsure what size you need, send us your appliance list or visit our shop. Our team will guide you through the numbers clearly and professionally. Get in touch with us today!