“How long will my battery last?” is the question we hear most. It has two answers: how many hours it runs your home tonight, and how many years it lasts before it needs replacing. Here are both, worked out for a 51.2V 100Ah (5.12kWh) lithium battery.

How many hours will it run my house?

Use this simple sum:

Hours of backup = usable battery energy ÷ average load

A 5.12kWh LiFePO₄ battery can safely deliver about 90% of its rating, so roughly 4.6kWh of usable energy. Allow a little for inverter losses and you have about 4.3kWh in practice.

• At 300W (lights, fridge, Wi-Fi, TV): about 14 hours
• At 500W (add laptops and a second fridge): about 8–9 hours
• At 1,000W (add a pump or frequent kettle use): about 4 hours

The fridge and lights run all night, but the kettle only runs for minutes, so work with your average load over the evening, not the peak.

When do I need a bigger battery?

If you want to get through a full evening and night with normal use, or run more than essentials, step up to the 10.24kWh (200Ah) or 16kWh (300Ah) battery, or add a second 5.12kWh unit. Our 51.2V batteries can be connected in parallel, so you can start with one and grow later.

How many years will it last?

Lithium iron phosphate (LiFePO₄) batteries are rated in charge cycles. Good A-grade cells are rated for 6,000 or more cycles. At one cycle a day that is well over 10 years before the battery drops to about 70% of its original capacity. That is why lithium has replaced lead-acid and gel batteries, which typically last only a few years. Read our LiFePO₄ vs AGM battery guide for the full comparison.

Three ways to make your battery last longer

• Set the correct battery type and voltages on your inverter. Wrong settings are the most common cause of early battery failure.
• Keep the battery in a cool, ventilated place, out of direct sun.
• Don't mix an old battery with a new one in the same bank.

How many solar panels do I need to recharge it?

South Africa gets roughly 4.5 to 6 peak sun hours a day. A 580W panel produces about 2kWh on an average day after losses, so three panels refill a 5.12kWh battery from empty on a clear day, and more panels let you run the house during the day at the same time. Our solar kits are already matched with the right number of panels.

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