Why Backup Power Matters
Power cuts in the UK may not be an everyday issue, but they do happen—especially during storms, grid maintenance, or unexpected faults. And when they do, they can cause real disruption. Whether you’re working from home, running a fridge full of food, or relying on medical or internet-connected devices, losing power even briefly is more than just inconvenient.
That’s why many homeowners are now considering home battery backup systems. With the right setup, a home battery can automatically provide electricity to essential devices during a blackout—keeping your home running smoothly, even when the grid goes down. But not all home batteries can do this by default. In this article, we’ll explore how home battery backup works, what you can realistically power, and what to consider when choosing a system for blackout protection.
Can a Home Battery Provide Backup Power?
Yes—but only if it’s designed to do so. While most home batteries store and manage electricity efficiently, not all systems provide backup power during a grid outage. Standard setups are often connected to the grid and shut down automatically during a power cut to protect utility workers from backfeed risks.
To provide true backup power, your battery system must be configured with a compatible hybrid inverter or backup inverter. These systems are capable of disconnecting (or “islanding”) your home from the grid safely and switching over to battery power automatically or manually. Without this feature, your battery will not function during a blackout—even if it’s fully charged.
So if backup power is a priority, be sure to choose a system that clearly supports it, and verify that your installer configures it for emergency use.
It’s also essential to understand that not all batteries can power the same types of appliances, even if they support backup. This depends on their discharge rate, or how quickly they can release stored energy. For example, some plug-in home batteries—designed to be installed without an electrician—usually have a maximum output of around 800 watts (0.8 kW). That’s enough for your internet router, phone chargers, and maybe a few lights, but not for a kettle or microwave.
In contrast, a fixed home battery system installed by a professional often delivers 2 to 5 kW of continuous output, which is enough to run several essential appliances at once, like a fridge, lights, Wi-Fi, and a washing machine—though you’ll still need to avoid using everything at the same time.
How Battery Backup Works During a Power Cut
In a properly configured home battery backup system, the transition is smooth and automatic. The moment a power cut is detected, your inverter isolates your home from the grid and begins drawing power from the battery instead. This switch usually takes just a fraction of a second—quick enough that most lights and appliances won’t even flicker.
The battery then supplies electricity to a dedicated backup circuit in your home. This circuit typically powers essential loads only, such as lighting, the refrigerator, Wi-Fi router, or charging points. The goal is not to power your entire home indefinitely, but to keep the most important systems running long enough for the grid to come back online—or until you can recharge the battery.
If your home also has solar panels, and your system supports it, you can even continue generating solar power during an outage. In that case, solar energy will recharge your battery during the day, extending your backup duration.
What You Can and Can’t Power
What your battery can power during an outage depends on two things: the battery’s capacity (in kWh) and its power output (in kW).
Most residential batteries range from 5 to 15 kWh in storage, and deliver 2 to 5 kW of continuous output. That’s enough to run low- and medium-load devices like: lights, internet router, Refrigerator/freezer, laptop or TV, phone chargers, gas boiler controls
However, heavy-use appliances like electric ovens, induction hobs, electric showers, or washing machines often require more power than a single home battery can safely supply. Unless you have a very large system or multiple batteries, these loads should be avoided during a power cut.
For most homeowners, the best approach is to prioritise essential items and avoid running everything at once. A good installer can help set up a separate backup circuit that automatically powers only what’s necessary.
What to Consider When Choosing a Battery for Backup
If blackout protection is one of your goals, make sure to look for a few key features when choosing a home battery system.
First, check that the system supports backup or emergency power mode. This typically requires a hybrid inverter capable of disconnecting from the grid safely. Brands like Tesla, GivEnergy, and Victron, among others, offer such functionality.
Next, consider the battery size. If you want backup for a few hours, a 5 to 7 kWh battery may be enough. For longer outages or more appliances, a 10+ kWh system will provide more flexibility. If you have solar panels, you’ll also want a system that allows solar charging during outages, which not all systems can do.
Another important detail is automatic switchover. Some systems require manual activation, while others detect an outage and switch instantly. Automatic changeover ensures that devices like your Wi-Fi or lighting keep working without interruption.
Finally, discuss with your installer about setting up a backup load panel—a separate circuit that includes only your most essential devices. This ensures your battery isn’t drained by non-essential items and gives you more control during an outage.