What Happens to Your Solar Panels During a Power Cut?
You’ve invested in solar panels, the sun is shining and your roof is generating electricity.
Then there’s a power cut.
Surely your house can just carry on running from the solar panels?
It’s a completely reasonable assumption but in most standard solar installations, the answer is no.
When the electricity grid goes down, a conventional grid-connected solar PV system will usually shut down too, even if your panels are capable of producing plenty of electricity at the time.
The good news is that solar technology has moved on considerably, and with the right battery storage and backup equipment, it is possible to keep your home – or selected circuits within it powered during an outage.
Why Do Solar Panels Switch Off During a Power Cut?
The reason is safety.
Most domestic solar systems are connected to the electricity grid. When your panels generate more electricity than your home is using, that surplus can be exported back to the grid.
During a power cut, engineers may be working on cables or equipment that would normally be considered disconnected from an electricity supply.
Your solar inverter therefore detects the loss of the grid and automatically stops supplying electricity. This prevents your solar system from continuing to energise the network while repairs are being carried out.
This safety feature is often referred to as anti-islanding.
So even on a bright summer afternoon, a standard grid-connected solar system will normally switch off when the grid does.
What If I Have a Solar Battery?
This is where things can get a little confusing.
A solar battery allows you to store electricity and use it later, but having a battery does not automatically mean your home will have power during a blackout.
Under normal operation, your battery works alongside the grid. It might store excess solar generation during the day and release that electricity later in the evening, or charge overnight using a cheaper electricity tariff.
But if your system hasn't been designed with backup capability, the inverter and battery may still shut down when the grid supply disappears.
For backup power, the system needs a safe way of separating your home from the electricity network and creating its own temporary supply.
This Is Where a Sigenergy Gateway Comes In
For customers who want greater energy independence, we can design a Sigenergy system incorporating a Sigenergy Gateway.
The Gateway monitors the grid supply and, if a power cut occurs, safely isolates the property from the electricity network before allowing the Sigenergy solar and battery system to continue supplying the home.
Rather than your solar installation simply switching off, your property can effectively operate independently from the grid for the duration of the outage.
When the mains electricity supply returns, the system reconnects and resumes normal operation.
Sigenergy designs its Gateway and SigenStor system specifically to provide this backup functionality and to manage the transition between grid-connected and backup operation.
Can Solar Panels Still Generate Electricity During the Power Cut?
With a correctly designed backup system, yes.
This is one of the biggest advantages of combining solar PV, battery storage and a Gateway.
Imagine the electricity goes off at 10am on a sunny day.
With a conventional solar installation, your system would shut down.
With a suitable solar, battery and Gateway setup, your panels can continue generating electricity for your home while also potentially replenishing the battery.
That can make a huge difference during a longer outage.
Instead of relying solely on whatever electricity happened to be stored in your battery when the power cut began, you potentially have another source of energy arriving every time the sun shines.
How Long Could a Battery Keep My House Running?
There isn't one answer because it depends on several things:
The size of your battery
How much charge was in it when the power cut started
How much solar your panels are generating
The amount of electricity your property is using
Which appliances you choose to run
The output capacity of the inverter and overall system design
A home using a few lights, Wi-Fi, televisions, refrigeration and other essential appliances is very different from one simultaneously running an electric shower, oven, EV charger, hot tub and heat pump.
This is why backup needs to be considered as part of the system design rather than simply adding the biggest battery possible.
At Optimum Electrics, we look at how you actually use electricity and what you would want to keep running if the grid went down.
Whole-Home Backup or Essential Circuits?
Backup systems can be designed differently depending on the property and the customer's priorities.
For some homes, whole-home backup may be appropriate, allowing the majority or all of the property to continue operating.
In other situations, it may make more sense to prioritise particular circuits or essential loads.
That could include things such as:
Fridges and freezers
Lighting
Wi-Fi and home networking
Security systems and CCTV
Heating controls
Selected sockets
Home offices
Medical or other important equipment
There is little point using valuable stored electricity on high-demand appliances during an outage if keeping your heating, lighting, fridge and internet running is more important.
A properly designed system takes this into account.
You Can Keep Electricity in Reserve for a Power Cut
Another useful feature of a battery backup system is the ability to retain some battery capacity specifically for emergencies.
With a compatible Sigenergy Gateway installation, a backup reserve can be configured within the mySigen system.
For example, rather than allowing the battery to discharge completely as part of your normal household energy use, you could choose to maintain a percentage in reserve.
If the grid then fails, that stored electricity is available for backup use.
The right reserve level will depend on how concerned you are about outages, your electricity consumption and how you want to balance everyday savings against backup protection.
Do You Need Battery Backup?
Not every homeowner needs it.
Power cuts in many areas of the UK are relatively infrequent, and some customers are primarily interested in solar and battery storage as a way of reducing electricity bills and increasing the amount of their own solar energy they use.
For others, backup capability can be extremely valuable.
You might work from home and rely heavily on your internet connection and computers. You may have electric heating equipment, security systems or refrigeration you don't want to lose. Or you may simply like the reassurance of knowing that a local power cut doesn't necessarily mean your entire house has to go dark.
For businesses, the impact can be greater still. Even relatively short periods of downtime can disrupt machinery, IT systems, production and trading.
The important thing is to discuss backup before the system is designed, so the correct equipment and electrical configuration can be incorporated from the outset.
Already Have Solar and Want Backup Power?
If you already have solar panels or battery storage, that doesn't necessarily mean you need to replace your entire installation.
Depending on the equipment already installed and the way the system has been configured, there may be options for upgrading or adapting it.
We can assess your existing installation, look at your electricity usage and discuss what you would realistically want to keep powered during an outage.
Thinking About Solar? Ask About Backup at the Design Stage
Solar panels aren't automatically a backup generator but modern solar and battery technology can give homeowners far more control over their electricity supply than a traditional solar-only system.
The important thing is designing it correctly.
At Optimum Electrics, we design solar PV and battery storage systems around how our customers actually use their homes. Whether your priority is reducing electricity bills, storing more of your own solar generation, taking advantage of cheaper electricity tariffs or adding whole-home backup, we'll help you understand the options.
Optimum Electrics is MCS, NICEIC and HIES accredited and an Octopus Energy Trusted Partner. We design and install solar, battery storage and EV charging systems across Cambridgeshire, Peterborough, Cambridge, Bedford, Northampton and Leicester.
📧 enquiries@optimumelectrics.co.uk | 📞 01733 601698
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