The Complete Guide to EPS and Home Backup
One of the most common questions we hear at SolarTherm UK is:
“If there’s a power cut, will my solar panels keep my house running?”
The answer surprises many homeowners.
In most UK homes, standard grid-connected solar panels automatically switch off during a power cut, even when the sun is shining. This is a safety feature known as anti-islanding protection.
However, a solar PV system fitted with a compatible battery, inverter and Emergency Power Supply (EPS) or other suitable backup equipment can continue supplying electricity during a power cut. Depending on the system, this may power a dedicated backup socket, selected household circuits or most of the property.
If you want your solar panels to keep generating electricity during a blackout, backup capability must be considered when designing or upgrading your system. Not every solar battery automatically provides backup power.
Why Do Solar Panels Switch Off During a Power Cut?
Most residential solar PV systems in the UK are connected to the National Grid. When the grid loses power, your inverter automatically shuts down. This is called anti-islanding protection.
It isn’t a fault with your system – it’s a legal safety requirement designed to protect engineers working on damaged power lines. Without this protection, your solar panels could continue exporting electricity into the grid, creating a serious safety risk. So even if your roof is generating electricity, your home will normally lose power unless your system has dedicated backup functionality.
How Can You Get Power-Cut Protection with Solar Panels?
If you want to keep your home powered during a power cut, having solar panels alone may not be enough. The level of protection you get depends on your inverter, whether you have battery storage, and whether your system has been designed to provide backup electricity when the grid goes down.
There are three main options to consider.
1. Solar Panels Without a Battery
Most standard grid-connected solar PV systems automatically shut down during a power cut. This is a safety feature known as anti-islanding protection, which prevents electricity from being exported to the grid while engineers may be working on the network.
Even if your solar panels are generating electricity in bright sunshine, your home will normally lose power when the grid supply fails. Without suitable backup equipment, your panels cannot provide electricity directly to your household during the outage.
2. Solar Panels With Battery Storage
Adding a solar battery allows you to store surplus electricity generated during the day and use it later, such as in the evening when your panels are no longer generating enough power.
However, having a solar battery does not automatically mean your home will have electricity during a power cut. Not all batteries and inverters support backup operation, and some installations require additional equipment or configuration to provide it.
If power-cut protection is important to you, check that your chosen system supports backup operation and that this functionality is included in the installation.
3. Solar Panels With EPS or Whole-Home Backup
For greater protection during a power cut, you can choose a compatible solar and battery system with an Emergency Power Supply (EPS) or another suitable backup arrangement.
Depending on the equipment and system design, this can provide electricity to a dedicated backup socket, selected household circuits or, where the installation supports it, most of your home. Essential appliances such as lighting, a fridge or your internet router may be kept running, provided the backup system has sufficient capacity.
Some systems can also continue using solar generation to recharge the battery during an outage, subject to the inverter’s capabilities, battery charge level, available sunlight and electrical configuration.
When choosing a solar installation, consider which appliances you want to power during an emergency, how long you need them to run, and whether you need backup for selected circuits or the whole property.
At SolarTherm UK, we can help you understand the solar and battery options available for your home, including whether a system with backup functionality could meet your requirements. The right solution depends on your property’s electrical setup, energy consumption and budget.
Can Solar Panels Work During a Power Cut?
Yes – but only if your system ahs the correct equipment. To continue using electricity during a blackout you’ll normally need:
- Solar panels
- Battery storage
- A compatible hybrid inverter
- Backup functionality such as an Emergency Power Supply (EPS) or whole home backup system (sometimes known as a Gateway)
Without these components your solar panels will shut down until grid power returns.
What Is EPS (Emergency Power Supply) in a Solar Battery System?
EPS stands for Emergency Power Supply. In a solar battery system, it is a backup function that allows compatible equipment to supply electricity to your home when the mains grid fails.
During a power cut, a standard grid-connected solar inverter normally shuts down to prevent electricity from being exported to the network. A system with suitable EPS or backup functionality can safely isolate the backed-up circuits from the grid and provide an alternative electricity supply.
Depending on the equipment and installation, this could power a dedicated backup socket, selected essential circuits or most of your property. However, not every solar battery or inverter includes this capability as standard.
Does EPS Work Automatically When the Power Goes Out?
That depends on the backup system installed.
Some systems automatically detect a grid failure and switch to backup power, potentially within seconds. Other arrangements require manual activation or have different switching procedures.
The changeover time also varies by equipment, so an interruption may still occur even with automatic backup. If you need uninterrupted power for sensitive equipment, check the manufacturer’s specifications and whether additional protection, such as an uninterruptible power supply (UPS), is required.
Your installer should explain how your particular system behaves during a power cut and which circuits will remain operational.
Can EPS Power Your Whole House?
EPS can power different parts of your home, depending on how the system has been designed.
- Backup socket: A dedicated socket supplies selected devices, such as a phone charger, laptop or broadband router.
- Essential circuits: Selected circuits, potentially including lighting, refrigeration and boiler controls, remain powered.
- Whole-home backup: A suitably designed system can supply most or all of your property, subject to its power output, electrical configuration and the appliances being used.
Whole-home backup does not necessarily mean you can operate every appliance simultaneously. High-demand equipment, such as electric showers, ovens and EV chargers, can exceed the inverter’s available output or rapidly deplete the battery.
The appropriate setup depends on which appliances you need during an outage, their starting and running power requirements, and how long you want them to operate.
Can Solar Panels Recharge a Battery During a Blackout?
Yes, some solar and battery systems can continue generating electricity and recharge the battery during a power cut, provided the inverter, battery and backup configuration support this operation.
This can help extend your backup supply during daylight hours. However, it is not guaranteed for every installation. Solar generation varies with sunlight, shading and weather, while the battery may have limits on its charging rate and available capacity.
If blackout operation is important to you, confirm that the proposed system can support solar charging while operating in backup mode. Your installer should also explain what happens when the battery becomes depleted or solar generation is insufficient to meet household demand.
Can EPS Be Added to an Existing Solar Installation?
In many cases, backup functionality can be added to an existing solar PV system, but compatibility needs to be checked before choosing the equipment.
The options depend on your existing inverter, battery (if fitted), electrical installation and the type of backup you want. Some systems support backup through additional equipment or configuration, while others may require a compatible inverter, a separate battery system or more substantial electrical modifications.
The installation may involve backup switching equipment, additional wiring, a dedicated backup consumer unit or changes to the circuits being supplied. All work must be designed and installed appropriately to maintain safe isolation from the grid during an outage.
Before upgrading, ask your installer to assess your existing system and confirm the equipment required, the circuits that can be backed up, and the expected performance during a power cut.
At SolarTherm UK, we can help you assess the options for your property and establish whether backup functionality can be incorporated into your existing installation or would be better planned as part of a wider solar and battery upgrade.
Which Battery Systems Support Backup?
SolarTherm UK supplies several battery systems capable of providing back up power.
- Hanchu ESS: Hanchu battery systems provide backup power to the level you require. Install an optional Gateway for full home backup.
- Tesla Powerwall 3: the Powerwall 3 includes integrated backup functionality, allowing seamless whole home backup.
- Sigenergy SigenStor: the SigenStor offers one of the most advances backup solutions available and can provide whole home backup when installed with the optional Gateway.
Can My Solar Panels Recharge My Battery During a Blackout?
Often, yes. Many modern hybrid battery systems continue using solar generation during daylight hours while operating in backup mode. This means your battery can recharge from your solar panels while the grid is unavailable, helping extend the amount of time your home can remain powered. The exact functionality depends on the equipment installed, so it’s important that your system is designed correctly from the outset.
How Long Will My Battery Last During a Power Cut?
There isn’t a single answer. Backup duration depends on:
- Battery capacity
- Household electricity usage
- Which appliances are running
- Solar generation during the outage
For example, running lighting, Wi-Fi and a fridge requires far less energy than operating an electric shower, oven or EV charger. Using only essential appliances can significantly extend the amount of time your battery provides power.
Is Backup Power Worth It?
For many households, standard solar panels and battery storage already provide excellent savings without backup functionality. However, adding EPS or whole home backup can provide valuable peace of mind. Backup can provide valuable peace of mind.
Backup power may be particularly worthwhile if you:
- Live in a rural area where outages are more common
- Work from home
- Have vulnerable family members
- Rely on medical equipment
- Simply want greater resilience
For others, a simple backup socket or essential circuits may provide all the protection they need. At SolarTherm UK we’ll discuss your requirements and recommend the most suitable level of backup for your property rather than a one size fits all solution.
What Does Installing EPS Involve?
Installing backup functionality requires additional electrical work beyond a standard solar installation. Depending on the level of backup selected, this may include:
- Additional consumer units
- Automatic transfer equipment or Gateway devices
- Backup circuit wiring
- Electrical isolation equipment
- System commissioning and testing
As every property is different, the exact installation requirements vary.
Choosing the Right Backup Solution
When designing a solar and battery system it’s important to think beyond today’s electricity bills.
Ask yourself:
- Do I want my home to stay powered during outages?
- Which appliances are essential?
- Would I prefer automatic or manual backup?
- Do I want whole home protection or just essential circuits?
Planning for backup during the initial installation is often the simplest and most cost effective approach.
Why Choose SolarTherm UK?
With over 16 years experience installing solar PV and battery storage across Essex, Kent, Suffolk, Hertfordshire and the wider South East and East Anglia, SolarTherm UK designs every system around the customer’s lifestyle and energy usage.
Whether you’re looking for a straightforward battery installation or a fully integrated whole home backup solution, our experienced team can recommend the right equipment to match your needs.
Contact SolarTherm UK today for a free, no obligation quote and design, tailored to your property, usage and future energy needs. No hard sell, just honest, expert advice – and the time you need to make an informed decision.
Your home. Your energy. Your future.
Frequently Asked Questions
Most standard grid-connected solar panel systems automatically switch off during a power cut because of anti-islanding protection. To continue using solar electricity during an outage, you generally need a compatible battery and inverter system with suitable backup functionality.
Not necessarily. A solar battery can store electricity for later use, but not every battery or inverter can supply power when the grid fails. Check whether your system supports backup operation and whether the necessary equipment has been installed.
EPS stands for Emergency Power Supply. It is a backup function that allows compatible solar and battery equipment to supply electricity to designated circuits or appliances when the mains supply fails. The amount of power available depends on the system’s design and capabilities.
Some EPS systems automatically detect a power cut and switch to backup power, while others may require manual activation. Changeover times also vary between systems. Ask your installer how your equipment operates during an outage.
Some systems can provide whole-home backup, but others only supply a dedicated socket or selected circuits. The available power depends on the inverter, battery capacity, electrical configuration and appliances being used. High-demand appliances may need to be switched off to avoid overloading the system.
Yes, some compatible systems can continue generating solar electricity and charging the battery during a power cut. This depends on the inverter, battery and backup configuration, as well as available sunlight and household demand. Not every installation supports solar charging in backup mode.
In many cases, backup functionality can be added to an existing solar installation. However, compatibility depends on your inverter, battery, wiring and the type of backup required. An installer can assess your existing equipment and recommend suitable options.
This depends on the battery’s usable capacity, its charge level when the power fails, the electricity demand of your backed-up appliances and whether solar panels can recharge it. Running essential appliances only can extend the available backup time.
Solar panels do not generate meaningful electricity at night. If your system supports backup operation, a charged battery can supply electricity to the backed-up circuits until its available energy is depleted. Without suitable backup equipment, the battery may not provide power during the outage.
A battery is commonly used to provide stored energy during an outage, but the exact requirements depend on the system design. Standard grid-connected solar panels generally switch off during a power cut. If you want backup power, your installer should confirm the equipment needed to operate safely when the grid is unavailable.
Depending on the system, you may be able to run lighting, a fridge, a broadband router, phone chargers and other essential appliances. The inverter’s power output, battery capacity and the appliances’ starting demands determine what can operate together. Electric showers, ovens and EV chargers may exceed the system’s available output.
Some solar and battery systems can operate in backup or off-grid mode when appropriately designed and configured. However, a standard grid-connected system may not operate independently of the grid without suitable equipment. Your installer can confirm whether your system supports this functionality.
Solar battery backup can be valuable if you want to keep essential appliances running during an outage, particularly where interruptions are frequent or disruptive. The benefits depend on the cost of the system, the equipment you need to power and how much backup capacity you require.
The cost depends on the battery capacity, inverter compatibility, backup equipment, electrical modifications and whether you are adding backup functionality to an existing installation or fitting a new solar and battery system. A site assessment is the best way to establish the cost for your property.
SolarTherm UK can help you explore solar PV and battery storage options, including systems designed to provide backup power during a power cut. The appropriate solution depends on your existing installation, electricity usage, budget and the appliances you want to keep running.
