Equipment and components
Battery (storage)
Also known as: storage, accumulator, solar battery.
Definition
A battery stores the energy the panels produce so it can be used later, for example at night or during a blackout. It adds autonomy and backup, but also cost, and its service life is shorter than the panels'.
On a grid-connected system with net metering, the grid already performs a function similar to a battery: it absorbs the day's surplus and returns energy at night. So in areas with a stable service, adding storage rarely improves the economic return; what it buys is not savings, it is backup during outages.
The relevant technical decisions are three. Usable capacity, in kWh, which does not match the nominal figure because a battery should not be fully discharged. The permissible depth of discharge, greater in lithium than in lead-acid. And service life, measured in charge and discharge cycles rather than in years: a battery cycled daily ages faster than one that only acts in emergencies.
Storage is clearly justified in two scenarios: sites with no grid access, where there is no alternative, and locations with frequent outages or critical loads — medical equipment, cold chain, servers, pumping — where the cost of being without power is high. In every other case it is worth assessing with concrete numbers before including it.
The essentials of Solar battery
- With a stable grid and net metering, a battery brings backup rather than savings.
- Usable capacity is lower than nominal: it is not discharged to 100%.
- Its life is measured in charge and discharge cycles, not just in years.
- It is the component that most increases the cost of a solar project.
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Related terms
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Frequently asked questions about Solar battery
Do I need batteries to save with solar panels?
No, if your system is grid-connected and has access to net metering: the surplus is offset on the bill and the grid acts as backup. Batteries are justified by autonomy during outages or by the absence of a grid, not by extra savings on the bill.
How long do solar batteries last?
It depends on the technology and the use. Lithium allows far more cycles and a greater depth of discharge than lead-acid, and so usually lasts considerably longer despite its higher up-front cost. The manufacturer's warranty is expressed in cycles or in total energy processed; that is the figure to compare.
Can I add batteries later on?
Yes, if the system is designed from the start with that in mind. It requires a hybrid or storage-compatible inverter, plus space and protections allowed for. Adding them to a purely on-grid system may mean changing the inverter, so it is worth deciding before buying.
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