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BatteriesWhat a gateway does, and when whole home backup is worth it
A battery full of electricity is no use in a power cut unless something tells it to run the house instead of the grid. That something is a gateway, and it is the piece most quotes leave out.
Updated 4 August 2026 · from the OVO Solar & Battery team
Why your solar switches off in a power cut
A standard grid connected solar system, and most battery systems with it, shut down the moment the grid goes down. This surprises almost everybody who has just spent five figures on a roof full of panels, so it is worth explaining properly.
The rule is called anti islanding. If the network goes dead, engineers have to be able to work on those cables knowing they are dead. A house quietly pushing power back out into the street would make that unsafe, so every compliant inverter is required to disconnect and stay disconnected until it detects a healthy grid again.
Backup is a hardware decision, not a software one
No setting in the app turns anti islanding off. Keeping power on through an outage means adding equipment that physically separates your home from the network first, then lets the battery energise the house behind that separation. That equipment is the gateway.
What a gateway actually does
A gateway sits between your meter and your consumer unit, which is to say between the grid and everything electrical in your house. It has four jobs, and it does them in this order.
It watches the grid
The gateway monitors incoming supply continuously, looking for the voltage and frequency signatures of a failure.
It islands the house
On a failure it opens the connection to the network, so your home is now electrically separate from the street. This is what makes it safe for the battery to take over.
It switches you onto the battery
The battery starts supplying the circuits behind the gateway. Published switchover claims range from effectively instantaneous on some products to a noticeable flicker on simpler arrangements.
It lets your solar carry on
With the house safely islanded, the panels can keep generating and recharging the battery, which is what turns a few hours of backup into potentially a few days in daylight.
A gateway also meters energy flows in both directions, which is how the system knows what you imported, exported, stored and consumed. That metering is what drives the time of use scheduling in normal operation, so it is not purely an outage device.
The three tiers of backup
Backup is not one product. There are three quite different levels, at three quite different prices, and a lot of confusion comes from people comparing quotes that are not offering the same thing.
| Tier | What you get | What it powers | Typical use case |
|---|---|---|---|
| EPS socket | A single socket wired from the inverter's emergency power supply terminals | One 13A outlet. A phone charger, a lamp, the broadband router | Cheapest option, occasional short outages |
| Partial backup | A sub board of selected critical circuits | Fridge and freezer, some lighting, broadband, a couple of sockets | Most households who want outage cover without the full cost |
| Whole home backup | A gateway or transfer switch covering the whole installation | Everything, subject to how much power the battery can push at once | Rural networks, home working, medical equipment |
Tiers as described across the UK installer market. Whole home backup is the most expensive of the three, and needs both the gateway hardware and enough battery power output to carry the house.
How long would it actually last?
Two numbers decide this: how much energy you have stored, and how fast your house is drawing it. A 5 kWh battery running a fridge, a freezer, lighting and a router at a combined 300W will keep going for the best part of a day. The same battery with an electric shower running, an oven on and an EV charging will be flat inside an hour.
This is why partial backup is often the sensible answer rather than the compromise answer. Putting only the circuits that genuinely matter behind the gateway makes your stored energy last many times longer, and stops the system emptying itself on a tumble dryer nobody needed to run.
Add daylight and the maths changes completely
In an outage with solar behind the gateway, the panels top the battery back up every day. A summer power cut can be ridden out almost indefinitely on a well sized system. A December one is a much shorter story, which is a reason to size storage against the worst case rather than the best.
If keeping the lights on matters where you live, say so when you book. Your local OVO expert will tell you on the free 45 minute design call what is realistic for your property, before anyone quotes you anything.
Get your free quote →Who should pay for whole home backup
- Rural properties on long overhead networks. If your street loses power in most winter storms, backup is buying something you will actually use.
- Homes with medical equipment. If something plugged in has to keep running, this stops being a comfort purchase.
- People who work from home. A day of lost work costs more than most people assume, and broadband plus a laptop is a very small load to carry.
- Anyone on a private water supply or with a septic pump. No power means no pump, and that becomes a problem faster than a dark kitchen does.
If none of those describe you, and your area loses power once every few years for twenty minutes, an EPS socket or nothing at all is a perfectly rational choice. Backup hardware is real money, and it should be bought for a real reason.
The bit that is not about power cuts
Worth being clear: backup capability does not change what your battery earns you day to day. The savings come from charging cheaply and discharging at peak, which is set out in the guide to off peak charging, and from the export rate on your surplus solar, covered on the export rates page. Backup is insurance bought alongside those, not instead of them.
Whatever you decide, the install is carried out by the regional partner business that holds the exclusive OVO partnership for your area, and covered by the OVO guaranteed 10 year workmanship warranty. Enter your postcode on the coverage page and it will tell you which local OVO expert looks after you.
Anything involving backup circuits needs a proper look at your consumer unit and your loads. That is a conversation for the design call, not a spreadsheet.
Backup questions, answered
Do solar panels work in a power cut?
On their own, no. A grid connected solar inverter is required to shut down when the network goes down, under the anti islanding rules that keep engineers safe while they work on the cables. Panels will only carry on generating during an outage if there is backup hardware in place to separate your home from the network first.
What is the difference between EPS and whole home backup?
An EPS is a single socket fed from the inverter's emergency terminals, good for a router and a lamp. Whole home backup uses a gateway to island the entire property and run it from the battery, which needs more hardware, more battery power output and more money. Between them sits partial backup, where a sub board carries only the circuits you choose.
How fast does the changeover happen?
It depends on the product. Manufacturer claims range from effectively instantaneous transfer, fast enough that a desktop computer will not notice, to a brief flicker on simpler EPS arrangements where you may need to restart something. If uninterrupted transfer matters for equipment in your house, raise it before the design is finalised rather than after.
Can I add a gateway later?
Physically it is possible, but it is not cheap. A gateway sits between the meter and the consumer unit, so retrofitting one means fresh electrical work at the heart of the installation and, depending on the arrangement, a return visit that costs far more than the hardware. If backup is even a maybe, it is worth designing for at the start.
Will backup keep my heat pump or EV charger running?
Usually not, and usually you would not want it to. Both are large loads that would drain a house battery very quickly, and both are normally left off the backup board deliberately so the stored energy goes to lighting, refrigeration and communications instead. Your design call is where those choices get made.
Does OVO fit whole home backup as standard?
Our standard specification is a 5.2 kWh usable battery designed around everyday savings rather than outage cover. If backup is important to you, tell your local OVO expert on the design call and they will explain what is possible on your property and what it would involve, in writing, on the call.
Figures and specifications in this guide are sourced below and were checked on the date shown. Rates and product specifications change; we confirm the current picture on your free design call.
Sources
- Anti islanding, why standard grid tied solar and storage shut down in an outage viablepower.co.uk
- Gateway function: grid monitoring, islanding, transfer and energy metering energylibrary.tesla.com
- The three tiers of backup, EPS socket, partial sub board and whole home via gateway solarlove.org
- Published switchover speed claims across current UK storage products heatable.co.uk
- Backup duration as a function of stored energy versus household load sunsave.energy
- When whole home backup is justified, rural networks, medical equipment and home working greenhatrenewables.co.uk
- OVO Solar and Battery published battery specification, warranty and SEG rates ovosolarandbattery.co.uk
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