Short answer: it depends entirely on whether your system has a battery. That’s the whole answer, really, but it trips up enough people that it’s worth spelling out properly — because “I have solar” and “I’m protected during a blackout” are not automatically the same thing, and we’ve met more than one disappointed homeowner who assumed they were.
Why some solar systems switch off during an outage
If your system is grid-tie — panels and an inverter, no battery — it is required by design to shut down the moment the grid goes down. This isn’t a glitch. It’s a safety feature called anti-islanding, and every properly certified inverter has it. The reason is simple: if your panels kept pushing power into the lines while KPLC technicians were out there trying to fix whatever caused the outage, it could seriously injure them. So the inverter detects the grid is down and cuts off automatically, batteries or no batteries.
Which means a grid-tie system, however well installed, gives you zero backup power during a blackout. It’s a brilliant tool for cutting your daytime bill. It is not a blackout solution, and anyone telling you otherwise either doesn’t understand their own system or isn’t being straight with you.
What actually happens with a hybrid or off-grid system
If your system includes battery storage — hybrid or off-grid — it’s a completely different picture. The inverter still detects the grid going down and disconnects from it, for the same safety reason as above. But instead of shutting your house off, it switches your home over to run from the battery instead, on an isolated circuit that doesn’t feed back into the grid lines. Properly configured, this switch happens in milliseconds — genuinely fast enough that most of our clients tell us they only know the power went out because they check their phone and see a KPLC outage alert, not because anything in the house actually flickered.
How long the battery actually lasts
This is where sizing matters more than almost anything else we talk about. A battery sized for occasional short outages — an hour here, two hours there — doesn’t need to be huge. A battery meant to carry a household through Nairobi’s longer scheduled outages, or an entire overnight stretch, needs real capacity, and that’s a conversation worth having honestly before you buy, not after your first long blackout leaves you in the dark at 11pm wondering why the “backup” ran out.
As a rough guide: a 5kWh battery will typically carry essentials — lights, fridge, router, a TV — through 4 to 6 hours comfortably. A 10kWh setup stretches that to closer to a full overnight. Beyond that, it comes down to what specifically you’re running; a household with an electric cooker or AC in the mix burns through stored power much faster than one running lights and a fridge.
What people usually get wrong
Two things, mostly. First, assuming any solar system equals backup power — it doesn’t, unless there’s a battery in it, as above. Second, underestimating their actual load when sizing the battery. People tend to think about the big, obvious appliances and forget the small stuff that adds up — routers, security systems, phone chargers, the fridge compressor cycling on and off through the night. A proper energy audit accounts for all of it; a guess usually doesn’t.
The bottom line
If blackout protection is actually why you’re considering solar — and for a lot of Kenyan homeowners, it’s the number one reason — make sure whatever system you’re quoted includes battery storage, and make sure the battery is sized around your real overnight and outage-duration needs, not just whatever fits the budget on the quote. A grid-tie system will save you money. It will not keep your lights on when KPLC goes down. Those are two different promises, and it’s worth knowing which one you’re actually buying.
If you’re not sure which category your current setup falls into, or you’re starting from scratch and want it sized properly the first time, get in touch — we’ll walk through your actual usage with you before recommending anything.
