What a battery is for
A battery stores electricity so you can use it later: in the evening, when your panels are not producing, or during load-shedding, when the grid is down. Along with a hybrid inverter, it is what turns a solar system from a bill-saver into a system that keeps your lights on when the power fails. See battery backup and energy storage for how we design one.
Lithium versus older battery types
There have historically been two families of home battery: lead-acid and lithium. Lead-acid is older and cheaper up front, but it does not cycle as deeply, needs occasional maintenance, and does not last as long. Lithium (LiFePO4) costs more to buy but lasts for thousands of cycles, needs no water top-ups, and holds its capacity better over time. For new installations we recommend lithium, because the cost over the life of the battery is usually lower even though the sticker price is higher.
Capacity, in simple terms
Battery capacity is measured in kilowatt-hours (kWh). Think of it as the size of the tank. A bigger tank runs your essentials for longer. The other half of the picture is power: a battery has to be able to deliver enough power at once to start a fridge or a pump. This is why we look at both capacity and the inverter's power rating, not capacity alone. A big tank that cannot pour fast enough will still trip.
How we size a battery
We start with the circuits you want to keep running if the power goes off. Then we work out how many hours of backup you need. From that we size the battery. A small household that wants lights, Wi-Fi and a fridge for a few hours needs far less than a home that wants a geyser or a pool pump to keep running. We will tell you honestly when the load you want is better served by a solar geyser or a smaller change than by a much bigger battery.
Cycle life and warranty
A battery's "cycle life" is how many charge-and-discharge cycles it can do before it fades to a percentage of its original capacity. Lithium batteries have long cycle lives; that is their main advantage. When you compare batteries, look at the cycle life, the usable capacity (not just the nominal figure), and the warranty. A five-year warranty on a battery that cycles daily tells you something about what the maker expects.
Adding a battery to an existing system
If you already have solar panels, you may be able to add a battery, but only if your inverter is hybrid or battery-ready. We check the inverter, the array and the wiring before recommending an option. In some cases the cleanest solution is to upgrade the inverter at the same time as adding the battery.
Where to go next
Read how solar and battery backup work and how to choose the best solar inverter in South Africa, or send us your bill and we will size a battery for your home.
Questions
Frequently asked questions
How big a battery do I need?
It depends on what you want to run and for how long. We add up the running load of your essential circuits and the hours of backup you want, then size the battery to that.
Is a lithium battery better than lead-acid?
For new installations, yes. Lithium batteries last longer, cycle deeper and need no maintenance. Lead-acid is cheaper up front but usually costs more over its life.
Can I add a battery to my existing solar system?
Often yes, if your inverter is hybrid or battery-ready. We check the inverter and the system before recommending a battery.