Solar batteries: when they make sense and what to check

Three different reasons to buy a battery

Before type and size, be clear why you need a battery at all, because each reason leads to a different design:

Backup during outages

Selected loads keep running when the grid goes down: fridges, internet, lighting, medical equipment in a clinic, pumps and tills at a petrol station. Size depends on those loads and the hours of backup.

More self-consumption

Storing daytime surplus for the evening instead of exporting it or drawing from the grid. The value depends on the gap between what exported and imported electricity are worth, and it is often weak.

Off-grid

No grid on site, so the battery is the only source of power after sunset. The question is not whether it is worth it, but how much you need and of what type.

When a battery doesn’t make sense

If your business uses most of its electricity by day, like a warehouse, school or office, a grid-tied system without batteries gives you most of the benefit. A battery adds significant cost, has a limited life and needs replacing years before the panels, without adding much to the savings.

In small homes with low bills, residential electricity in the Kingdom is relatively cheap, so paying back panels from savings alone can take a long time, and a battery stretches it further. If saving money is your only reason, it is usually better to start without a battery, with an inverter that can take one later. If outages genuinely bother you or you need backup for important equipment, that is a legitimate reason; just size it sensibly.

Lithium or lead-acid?

Most new systems use lithium iron phosphate (LFP) batteries. They handle many more charge and discharge cycles, let you use more of their capacity, need no routine maintenance and are more stable than other lithium chemistries. They cost more up front, but their longer life usually makes them cheaper over the years of operation.

Lead-acid batteries, sealed or flooded, are older technology and cheaper to start with, and still appear in small systems or backup that is rarely used. But they suffer more in heat, lose much of their life if repeatedly discharged deeply, and some types need monitoring and ventilation because they release gas while charging. In an off-grid system cycled every day through a Saudi summer, the difference shows quickly.

Either way, the battery should be from a recognised class, meet the standards and be compatible with the proposed inverter, not simply the cheapest line in the quote.

Cycles, depth of discharge and warranty terms

A cycle is one charge and discharge. Depth of discharge is how much of the capacity you use in each cycle. The deeper each discharge, the fewer cycles the battery lasts. So the capacity printed on the battery isn’t enough: ask for the usable capacity, and for the depth of discharge behind the cycle figure in the datasheet.

Battery warranties are more complicated than panel warranties. Some run for a number of years, some for a number of cycles or a total amount of energy through the battery, whichever comes first. The manufacturer usually guarantees the battery keeps a stated share of its capacity at the end of the term, not that it stays as new. Read the temperature conditions too: some warranties require the battery to be installed within a set temperature range and may be void in a hot, unventilated space.

Ask for all of this in writing: battery type, usable capacity, warranty length and conditions, and who handles claims. More in our warranties and maintenance guide.

Heat and where to install

Heat is a battery’s worst enemy in Saudi Arabia. A battery in a moderate room lives far longer than the same battery in a metal enclosure on a roof in midsummer. So location isn’t a detail for the last day; it is part of the design.

At an istiraha near Riyadh, the usual solution is a small shaded, well-ventilated room for inverters and batteries, out of direct sun and away from bedrooms and guest areas, with room for maintenance. Large sites may use dedicated battery cabinets with their own cooling. In every case, ask the installer where the batteries will go, how they will be protected from heat, and whether the location meets the warranty conditions.

Safety: not the place to save money

Batteries store a lot of energy in a small space, and a mistake in installation or protection can cause a fire. A good battery comes with a management system (BMS) that monitors temperature, voltage and current and disconnects it when there is a risk, and it must be correctly integrated with the inverter.

Battery locations, indoors or outdoors, may be subject to Civil Defense requirements and standards on ventilation, fire resistance and distance from occupied rooms. We don’t give details here because they need confirming with the authorities, but the principle is clear: installing and connecting batteries is work for a licensed electrical contractor who knows these requirements. Don’t connect batteries to the inverter or switchboard yourself.

How to choose the right size

Start with a list of the loads that must run on the battery and for how many hours. Two fridges, internet and lighting for a few hours are very different from running air conditioners all night. The engineer works out the daily consumption of those loads in kWh, adds a margin for losses, heat and ageing, and chooses a usable capacity that covers it.

For backup, size is set by the outages you actually get, not the worst case you can imagine. For an off-grid system, it is based on night-time use and days of autonomy, with a generator covering rare cases instead of huge batteries that sit unused most of the time. For the differences between systems, read off-grid, hybrid or grid-tied; service details are on solar batteries.