Solar Battery Backup for Power Cuts in Ireland
Storm Éowyn cut power to 768,000 homes, farms and businesses on 24 January 2025, and the last homes were not reconnected until 11 February. Since then, many people getting solar have asked the same question: will my panels keep the lights on in the next one? On their own, no. With the right battery and backup hardware, yes. This guide explains the options, which brands support them, what they cost and who they suit. For live outages, see the ESB power outage map.
Quick Answer
A standard solar system in Ireland switches off in a power cut, even on a sunny day, so it cannot feed electricity onto a line that ESB crews are repairing. To keep power on you need a battery with backup: either an EPS (emergency power supply) output on a hybrid inverter that runs a few essential circuits, or a backup gateway that disconnects the whole house from the grid and runs it from the battery. Backup hardware is usually an extra on the quote. ESB Networks requires solar or batteries used for standby power to be installed and tested by a Registered Electrical Contractor, with a changeover device that breaks the connection to the grid.
What a standard solar system does in a power cut
Almost every home system in Ireland is grid-tied: the panels and battery run alongside the ESB supply. When the grid fails, the inverter switches itself off. This is a safety feature required of every inverter connected to the network (they must meet the EN 50549-1 standard), and it stops your system pushing electricity onto a line that crews believe is dead.
So without backup, your panels and even a fully charged battery sit idle until the grid is back. Having a battery is not enough on its own: it needs a way to disconnect the house from the grid and run it as an island.
The three ways to get backup
EPS / backup output on a hybrid inverter
A separate output on the inverter feeds a small set of essential circuits (lights, fridge, broadband, a few sockets) from the battery and panels when the grid fails.
Covers: Essential circuits only
Cheapest route. Limited by the inverter's backup power rating, so no electric shower, oven or immersion.
Backup gateway or backup box
A unit at the main board that detects the outage, disconnects the house from the grid and lets the battery run the circuits wired through it.
Covers: Whole home or selected circuits, depending on how it is wired
Needed for backup on Tesla Powerwall 3, Sigenergy and Huawei systems. Usually a separate line on the quote.
Manual changeover switch
A switch you flip to move a set of circuits from the grid to the battery or a generator.
Covers: Whatever is wired to it
Not automatic: the power goes off until you switch over.
Whole home or essential circuits?
Essential-circuit backup keeps the things that matter running: lights, fridge and freezer, broadband, phone chargers, the boiler controls and pump, and a socket or two. It needs less battery and a smaller inverter, and the battery lasts much longer because the load is small.
Whole-home backup keeps everything wired as normal, but the battery and inverter must handle every load you switch on. An electric shower, oven or immersion can overload a typical home inverter or drain the battery in an hour or two. If you go whole-home, plan to avoid the heavy loads during an outage.
Backup by brand
Switchover time matters for computers, routers and medical devices: a few milliseconds goes unnoticed, while a few seconds will reboot anything without its own battery. Figures below are the manufacturers' published specifications; check the exact model on your quote.
| System | Backup hardware | What it covers | Switchover |
|---|---|---|---|
| Tesla Powerwall 3 | Backup Gateway 2 (separate unit) | Whole home or selected loads, chosen at design stage | Automatic |
| Sigenergy SigenStor | Sigen Gateway (optional extra) | Whole home or selected loads | 0 ms on the load side (manufacturer datasheet) |
| Solis S6 hybrid | Built-in backup port | Circuits wired to the backup port | Under 10 ms; under 4 ms quoted for single-phase S6 models |
| FoxESS H1 | Built-in EPS output | Circuits wired to the EPS output, up to 5,000 to 6,000 VA | Under 20 ms (product parameters) |
| Huawei SUN2000 + LUNA2000 | Backup Box B0 (single phase) or B1 (three phase) | Circuits wired through the backup box | Under 3 seconds for the B1 (manufacturer spec) |
Closed systems (Tesla, Sigenergy, Huawei) need the maker's own gateway or box. Open hybrid inverters such as Solis and FoxESS have the backup output built in, but it still has to be wired to a separate backup board. See the inverter comparison for the wider pros and cons, and the Sigenergy gateway and Tesla Powerwall reviews for those systems.
How long will the battery last?
Divide the usable battery capacity by what the house draws. As an illustration, a 10 kWh battery with about 9 kWh usable, running essential loads that average 500 watts, lasts around 18 hours. Add a kettle, toaster and washing machine and it falls fast. In daylight the panels top the battery back up, but in a winter storm they may add little.
Many systems let you set a backup reserve, a share of the battery that is never used day to day so it is always there for an outage. When a storm is forecast, raise the reserve or charge the battery fully from the grid the night before. See what size battery you need.
What backup costs
| Item | Typical cost |
|---|---|
| 5 kWh battery, added to existing solar | €4,200–€5,500 installed |
| 10 kWh battery, added to existing solar | €5,500–€8,000 installed |
| SEAI battery grant (5 kWh or more) | −€600 |
| Backup gateway or backup box, plus a backup board | Extra on top; ask for it as a named line on the quote |
The battery is the big cost; the backup hardware and the electrician's time to split out a backup board add to it. A battery fitted at the same time as the panels is cheaper than one added later. See solar battery prices and the battery grant. The grant pays for the battery, not for backup hardware on its own.
Generator or battery?
| Battery with backup | Standby generator | |
|---|---|---|
| Switchover | Automatic, milliseconds to seconds | Manual or automatic start, then changeover |
| Runs for | Hours, longer with sun or light loads | As long as you have fuel |
| Day to day | Saves money on every bill | Sits idle |
| Noise and fumes | None | Yes; must run outdoors |
| Grant | €600 SEAI battery grant | None |
For outages of a few hours, a battery is the easier answer. For multi-day outages like Storm Éowyn, the battery will run down unless the sun comes out, so some rural homes keep a generator too. Some backup gateways can also take a generator input.
The safety rules
- ESB Networks says solar panels, batteries and EVs can be used for standby power in a loss of supply, but they must be designed, installed and tested by a Registered Electrical Contractor.
- There must be an appropriate changeover switch (or automatic equivalent) that breaks the connection with the ESB supply, so nothing feeds back onto the network.
- If ESB finds a property feeding power onto the network during an outage, it disconnects the whole property on safety grounds, and only reconnects once a Registered Electrical Contractor submits a wiring certificate for the entire installation.
- Never plug a generator or battery into a socket to back-feed the house. It can kill ESB crews working on the line.
Who backup suits
- Rural homes at the end of long overhead lines that lose power in most storms
- People who work from home and need broadband and a laptop running
- Homes with a well pump, so you keep water during an outage
- Anyone relying on medical equipment at home
If you rely on medical equipment, a battery is a help, not a replacement for registering as a vulnerable customer with your electricity supplier. See vulnerable customers on our outage page. If you are still planning your system, our beginner's guide to getting solar covers the full process.
Battery backup: FAQ
Do solar panels work during a power cut in Ireland?
Not on a standard system. Grid-connected inverters switch off when the grid fails so they cannot feed power onto a line being repaired. To keep power on you need a battery with backup: an EPS output on a hybrid inverter or a backup gateway.
Does a solar battery work in a power cut?
Only if it has backup hardware. Without an EPS output or a backup gateway, the battery switches off with the inverter. Tesla Powerwall 3 needs a Backup Gateway 2, Sigenergy needs the Sigen Gateway, and Huawei needs a Backup Box; Solis and FoxESS hybrids have a backup output built in.
What is EPS on a solar inverter?
EPS stands for emergency power supply. It is a separate output on a hybrid inverter that runs a set of essential circuits from the battery and panels when the grid fails. It is limited by the inverter's backup rating, so it suits lights, fridge and broadband rather than showers or ovens.
Can I back up my whole house with a solar battery?
Yes, with a whole-home gateway such as Tesla's Backup Gateway 2 or the Sigen Gateway. But the battery and inverter must cope with every load you switch on, so heavy loads like an electric shower or immersion should be avoided during an outage.
How long will a solar battery power my house in a power cut?
Divide usable capacity by your load. A 10 kWh battery with about 9 kWh usable, running essential loads averaging 500 watts, lasts around 18 hours. Heavier use cuts that sharply; sunshine during the day tops it up.
Is the SEAI battery grant available for a backup battery?
Yes, the battery qualifies if it is 5 kWh or more and the home was built and occupied before 2025. The grant is €600. It does not pay for backup hardware on its own.
Who can install battery backup?
ESB Networks requires solar, batteries or EVs used for standby power to be designed, installed and tested by a Registered Electrical Contractor, with a changeover switch that breaks the connection to the ESB supply.
Related Guides
Sources
- ESB Networks: Standby generators (changeover switch, Registered Electrical Contractor, solar and batteries as standby), esbnetworks.ie
- ESB Networks: Micro-generation (EN 50549-1 inverters, changeover switch for standby use), esbnetworks.ie
- ESB Networks: Unprecedented damage to the electricity network by Storm Éowyn (26 Jan 2025), esbnetworks.ie
- The Irish Times: Power finally restored to all homes and businesses following Storm Éowyn (11 Feb 2025), irishtimes.com
- Tesla: Powerwall 3 owner manual, system design (whole-home and partial-home backup with Backup Gateway 2), energylibrary.tesla.com
- Sigenergy: Sigen Gateway HomePro datasheet (0 ms load-side switchover), cdn.estg.eu
- FoxESS H1-3.0-E parameters (EPS output 5,000 VA, transfer time under 20 ms), 7sun.eu
- Solis S6 6kW single-phase hybrid listing (backup switchover under 4 ms), qualityheating.co.uk
- Huawei Backup Box B0/B1 technical specification (B1 switchover under 3 s), jubailibros.com
Facts checked on 4 November 2026.
Fact-checked by John Rooney, Solar Energy Editor. Editorial policy
John Rooney is the editor of Solar Info and has been covering the Irish solar energy market since 2023. He fact-checks all content against official SEAI data and maintains relationships with SEAI-registered installers across Ireland.
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