What a battery gateway actually does

The problem a gateway solves

A standard grid tied solar and battery system disconnects itself the instant the grid goes down. This is not a fault. It is a safety requirement called anti islanding, and it exists to protect the engineers working on the network from a house quietly pushing power back into a line they believe is dead.

The consequence catches people out every winter. You can have a full battery, a bright day and 6 kWp on the roof, and still sit in the dark with the rest of the street. Getting round that needs dedicated hardware, and the most capable version of that hardware is a gateway.

What the box actually does

A gateway sits physically between your meter and your consumer unit, so every amp entering or leaving the property passes through it. From there it performs four jobs.

1. It monitors the grid continuously, watching voltage and frequency for the signature of an outage.
2. It disconnects the property from the network when the grid fails, creating a safe electrical island that cannot back feed the street.
3. It switches the home onto the battery, and lets the solar array carry on generating into that island so the battery can recharge while the outage continues.
4. It meters energy flows in both directions, which is what makes accurate self consumption tracking and time of use scheduling possible in the first place.

That fourth job is the one people forget. Even in homes that never lose power, the metering a gateway provides is what lets the control software know exactly what the house is importing and exporting at any moment, which is the basis of sensible off peak charging decisions.

How fast the switchover happens

Speed matters more than it sounds. A slow transfer means everything with a clock resets, the broadband router reboots, and anything mid cycle stops. A fast one means the lights flicker and nothing else notices.

Sigenergy claims a 0 millisecond switchover on the SigenStor, which is uninterruptible power supply territory, and also quotes 200% peak output when running off grid so the system can absorb motor start up surges. Simpler emergency power supply modes wired straight from an inverter are slower and typically produce a visible flicker or a brief dropout.

Gateways are not the only way to get backup

There are three tiers, and the price gap between them is significant. Buying the top tier when the middle one would do is the most common way people overspend on a battery quote.

Whole home backup is the most expensive of the three. Which one suits depends on what you actually need running, not on what sounds most complete.

Our guide to whole home versus partial backup works through the runtime arithmetic for each tier, including how long a given battery lasts against a given load.

When a gateway is worth the money

Honestly, for a lot of suburban homes on a stable network, it is not. Outages are short and infrequent enough that the cost of whole home backup buys a lot of electricity. The calculation changes sharply in four situations.

• Rural properties on overhead distribution networks, where outages are longer and more frequent.
• Homes with medical equipment that cannot tolerate an interruption.
• Households where someone works from home and a day offline has a real cost.
• Properties with septic pumps, borehole pumps or other infrastructure that stops working the moment power does.

If none of those apply, the middle tier usually wins. A partial backup sub board covering the fridge, the freezer, a lighting circuit and the router costs materially less than whole home backup and covers the things that actually cause damage or disruption when they stop.

The cost implication on a quote

Gateway hardware shows up as a line item. Tesla, for example, lists the Powerwall 3 from £5,000 without a gateway and from £5,975 with one before installation, so the gateway itself accounts for a visible chunk of the difference. Fully fitted, a single Powerwall 3 with Backup Gateway is commonly quoted around £7,995. Our 2026 battery costs guide breaks the rest of that down.

Whatever the hardware costs, the labour is the other half of the story. Whole home backup means work at the consumer unit and the incoming supply, which is more involved than hanging a battery on a wall. That is one reason it is far cheaper to specify backup at the start than to add it later.

Rules and permissions

Backup hardware does not change the Distribution Network Operator picture on its own, because assessment is based on inverter rating. G98 covers up to 16A per phase, which is 3.68 kW on single phase, and can be installed then notified within 28 days. Anything above that needs a G99 application approved before the work. Ofgem's connection guaranteed standards give the DNO 45 working days to issue a quotation for a low voltage generation connection, and type tested systems under 50 kW are usually decided faster than that in practice. Ratings are assessed cumulatively, so a 3.5 kW battery inverter added to a 3.5 kW solar inverter puts the site into G99 territory.

The battery storage guide covers the wider product picture, solar panels covers generation, and every county page in our coverage area carries a local calculator.

Product specifications checked 3 August 2026. Clearline gives independent guidance and a free remote design call. Installations are carried out by an MCS-certified installation team for your area.