The power goes off at 6pm, the neighbours’ lights are out, and you glance at your solar app showing you generated plenty earlier. The obvious question lands fast: if you’ve got panels on the roof, why can’t you just use that electricity right now?
For most UK homes, the answer is frustrating but deliberate. A standard grid-tied solar PV system is designed to switch off during a mains outage – even on a bright day – unless it has specific backup hardware. That behaviour isn’t a fault. It’s a safety requirement.
Does a solar inverter work in a power cut?
It depends what you mean by “work”. In a typical solar PV setup, your inverter will detect the grid has failed and will shut down automatically. That means no export to the grid, and usually no power to your home circuits either.
This is built into virtually all standard inverters because of anti-islanding protection. In plain terms: if the grid is down, your inverter must not keep pushing electricity into the network. Engineers could be repairing a fault nearby, and a house continuing to energise the lines would create a serious risk.
So if you have:
- Solar panels
- A standard grid-tied inverter
- No battery and no backup gateway
…you should expect the system to stop supplying power during a cut.
Why solar shuts down when the grid fails
Your inverter normally synchronises to the grid’s voltage and frequency. It uses that stable reference to convert DC electricity from the panels into usable AC electricity for your home.
When the mains fails, that reference disappears. Without additional equipment, the inverter cannot safely form its own stable “mini-grid” inside your home, and it must disconnect. This isn’t installers being cautious – it’s mandated by UK grid connection rules and is part of the compliance package that protects homeowners, network engineers, and your equipment.
The key point: solar panels don’t “power the house directly”. They feed DC into an inverter, and the inverter is the traffic controller. If the controller has to shut down, your usable solar power shuts down with it.
The common scenarios homeowners actually have
1) Solar PV only (no battery)
During a power cut, your inverter switches off. Even if the sun is shining, the house is typically without power. When the grid returns, the inverter will perform its normal safety checks and restart.
2) Solar PV plus battery storage (without backup capability)
This is where expectations can get muddled. Many battery systems are installed primarily for bill reduction: charge from solar, discharge in the evening, and reduce peak-rate imports. If the system is not configured with backup functionality, it will also shut down in a mains outage.
You may have a battery sitting there with charge available, but the system is still grid-tied and still required to isolate.
3) Solar PV plus battery storage with backup (EPS/backup gateway)
This is the setup that can keep essential circuits running when the mains fails.
In this configuration, the system isolates from the grid and forms a safe supply to your home (or to a dedicated “backup circuits” board). Your inverter and battery effectively create a small islanded network for your property, powering selected loads. If solar generation is available, it can continue charging the battery and supplying those loads while the grid is down.
The difference here is not the panels. It’s the inverter capabilities and the extra equipment and wiring that allows safe islanding.
Backup power: what you need (and what you don’t)
If your goal is power-cut resilience, you need three things designed to work together:
First, an inverter and battery system that supports backup operation (often called EPS, backup, or off-grid mode). Second, a method of automatic disconnection from the grid (typically a backup gateway or integrated changeover) so there’s no risk of energising the network. Third, an agreed plan for which circuits you want to run, because most homes cannot back up everything economically.
What you don’t need is guesswork or “we’ll just wire it in”. Backup is a safety-critical design choice and should be specified at quotation stage, not bolted on as an afterthought.
What will you be able to run in a power cut?
Backup isn’t usually about keeping your whole house exactly as normal. It’s about keeping the important things on.
In practice, most households choose a set of essential circuits: broadband router, lights in key rooms, fridge/freezer, phone charging, perhaps the boiler controls, and a few sockets for working from home. High-power loads such as electric showers, immersion heaters, ovens, and some EV chargers can overwhelm a backup supply quickly.
A good installer will talk you through realistic expectations based on:
- Your battery capacity (kWh) – how long you can run for
- Your inverter’s backup power rating (kW) – what you can run at once
- Your starting currents – some motors and compressors draw a brief surge
If you want more than “essentials”, it may be possible, but it changes the system design. Sometimes that means a larger inverter, more battery modules, or a different approach for three-phase and light-commercial sites.
Will solar panels keep charging the battery during an outage?
With a proper backup setup, yes – with conditions.
If there’s daylight and your PV is producing, the inverter can use that generation to support the backup loads and charge the battery. If there’s no sun, you’re running purely on stored energy.
There are two practical limitations people notice:
One is that PV output can fluctuate quickly with cloud cover. Your backup supply needs to remain stable, so the battery often acts as the buffer, smoothing out peaks and dips.
The second is that some systems restrict PV generation while islanded to protect the battery and maintain stability. That’s normal behaviour and part of safe design. It’s also why a proper commissioning and configuration matters – a “backup capable” product still needs to be set up correctly.
What about “black start”?
In plain English, black start means the battery and inverter can start up and supply power even when the grid is already down.
Some systems require the grid to be present to wake up fully; others can start from the battery, form the supply, then bring PV online. If backup is central to why you’re investing, ask this question explicitly. It changes what happens if you wake up to an outage rather than experiencing a cut while the system is already running.
Trade-offs: backup vs maximum savings
Most people buy solar and storage to reduce bills first, then discover backup is possible and want it too. It usually can be done, but there are trade-offs.
When you design for backup, you may accept extra hardware, more complex wiring (often a separate consumer unit for backed-up circuits), and sometimes slight efficiency differences depending on how the system manages islanded operation.
You also need to decide how “automatic” you want it. Some setups switch over in seconds; others involve a manual changeover or a planned process. Automatic backup is generally the most convenient, but it requires the correct gateway and configuration.
Retrofitting backup to an existing solar system
If you already have solar PV, adding a battery is a popular upgrade. Adding backup is possible in many cases, but not always as simple as swapping a box on the wall.
The feasibility depends on your existing inverter type, your earthing arrangement, available space for additional protection devices, and how your current consumer unit is laid out. Sometimes an AC-coupled battery makes sense for retrofit savings, but you still need to ensure the backup method is compliant and safe.
For some properties, it’s cleaner and more cost-effective to move to a system designed as an integrated solar and storage platform, especially if you want a tidy, documented backup solution with clear warranties and support.
What to ask an installer before you commit
If your goal includes power-cut coverage, you’ll get better results by asking direct questions early.
Ask whether the proposed inverter and battery support EPS/backup, and whether that includes black start. Ask what loads they recommend backing up and how they’ll separate those circuits. Ask what happens during the switchover – will lights flicker, will the router drop, how long is the interruption. And ask for the backup power rating in kW, not just the battery size in kWh.
Finally, ask what standards and consumer protections sit behind the work. Solar and storage are long-term assets. You want an installer who designs properly, installs to UK standards, and can support you later with documentation, warranties, and service.
If you’d like a quotation that’s designed around both savings and outage resilience, Home Energy Group Ltd can specify systems with battery storage and power-cut backup options, with the reassurance of strong compliance credentials and insurance-backed guarantees.
The honest answer to “will solar keep me powered?”
A standard solar inverter will not keep your home running in a power cut, and that’s exactly how it should behave for safety. If backup matters to you, plan for it deliberately: choose the right inverter and battery platform, add the correct gateway or changeover equipment, and decide which circuits you actually want to protect.
The most reassuring part is this: once backup is designed properly, it stops being a gimmick and becomes a practical feature you notice only when you need it – when the street goes dark and your essentials stay on without fuss.