If your inverter is EPS-capable but your circuits go dark in an outage, common causes include a wiring fault on the EPS circuit, a missing or doubled neutral-earth reference, or a setting. We diagnose and fix EPS configuration issues as part of our fault diagnosis service.
Book EPS diagnosis / installationRemote EPS fault diagnosisI had a red status light on my GivEnergy battery pack and Ron at Solar Tech Support was a great help resolving the problem. He was able to do a remote diagnosis of the invertor BMS firmware and hardware and gave very quick practical and professional support. Thanks Rob
Great service from STS after a power cut and brownout left my GivEnergy inverters effectively useless. After filling the enquiry form out I was promptly given clear instructions by email explaining how to run their diagnostic software and they were working remotely in minutes. Soon after my inverters were back running again. Very helpful and knowledgeable people - thank you.
This is the second time I have used Solar tech first time a faulty Givenergy inverter, tried all sorts to get it going my last call was to Solar tech and yes they got me back up and running, today system went down again due to a firmeware update and Ron talked me through everything all whilst he was on someone’s roof sorting their system out. I would recommend this chap to every body that has problems with their system no matter what make..
The ONLY technical person, who has ever exceeded my own high standards !!!! Being a professional commissioning engineer of over 37yrs in the field of emergency power generation, I approached Ron for some advice on a GivEnergy battery issue as happy to state I don't know everything. Not only did he reply immediately, his advice got the system working and all on a Sunday. You really do not get support as good as this anywhere now for anything. Thank you Ron
I reached on behalf of a friend, who had lost control of their battery following a storm. A couple giv energy “dealers” had attempted and said different fixes. None worked. Solar tech support solved it remotely on the first attempt almost instantly. Genuinely a 10/10 service.
Absolutely fantastic experience, after months of being fobbed off with rubbish from the installer Ronald fixed my issues in a few hours, his attention to detail and his tenacity was amazing, not only did he go above and beyond but did not ask for payment i had to ask him how to pay. If you need a solar fix this company is brilliant
EPS is a feature built into most modern hybrid solar inverters. When the grid supply fails, the inverter automatically disconnects from the grid and switches its output to protected circuits — powered entirely by your battery. How long the switch takes depends on the system. On GivEnergy hybrid and AC-coupled inverters we see about a second: lights go off briefly and a desktop computer without a UPS will switch off. A GivEnergy All-in-One with a Giv-Gateway switches in about 20 ms. Fox ESS prints the switch-over time for the H1 and H1-G2 as under 20 milliseconds on the inverter's own EPS output (its newest H1-G2 datasheet says under 10), and under 3 seconds on the H1-G2 through the EPS BOX-SP.
How much of your home gets protected depends on which EPS configuration you choose. A simple wall socket keeps one or two appliances alive. A full-house automatic changeover switch protects every circuit in the building, with no manual switching.
Important: Enabling EPS mode in your inverter settings alone is not sufficient. You must have physical EPS wiring — whether that is a dedicated socket, a sub-board, or a changeover switch. Without the electrical work, enabling EPS mode has no practical effect and the inverter will still shut down your circuits when the grid fails.
EPS is not one-size-fits-all. There are four distinct ways to wire EPS backup power, each offering a different level of coverage, complexity, and cost. The right choice depends on how many circuits you want to protect and whether you need automatic or manual switchover.
A single 13A socket wired directly from the inverter's EPS output terminals. During a power cut, this socket stays live while the rest of the house goes dark. You plug in whatever you need most — a phone charger, broadband router, or extension lead to a fridge-freezer.
Typical use: Keep the broadband router and a phone charger running during short outages. Suited to households that rarely experience power cuts but want basic resilience.
A separate EPS consumer unit (sub-board) wired from the inverter's EPS output terminals. Selected circuits are moved onto this sub-board — typically lighting, essential sockets, boiler, freezer, and broadband router. During a power cut, only these protected circuits stay live. The rest of the house remains off until the grid returns.
Typical use: The standard recommendation for most homes. Protects 3–8 essential circuits. Battery lasts longer because high-draw circuits (cooker, shower) stay off.
A manual changeover switch (typically a rotary isolator) is installed between the grid supply and your main consumer unit. When the power goes out, you physically turn the switch to transfer the entire consumer unit from grid supply to inverter EPS output. Every circuit in the house is then powered by the battery. When the grid returns, you switch it back.
Typical use: Households that want full-house coverage without the cost of automatic changeover. You need to be home (or have someone home) to operate the switch when the grid fails.
An automatic changeover switch (ATS) monitors the grid supply continuously. The moment the grid fails, the ATS transfers the entire consumer unit to inverter EPS output — automatically and without any manual intervention. When the grid returns, it switches back. While the grid is off, the whole house runs from the battery, after a short gap at the switchover: about a second on GivEnergy hybrid and AC-coupled systems, in our experience.
Typical use: Households that want the whole house covered automatically. Ideal when people are often away or when there are vulnerable occupants. Anything that cannot take even a short break in power (medical equipment, a desktop computer, some security systems) also needs its own UPS.
| Feature | Wall socket | Dedicated circuit | Manual changeover | Auto changeover |
|---|---|---|---|---|
| Circuits protected | 1 socket | 3–8 selected | All | All |
| Automatic switchover | Yes | Yes | No (manual) | Yes |
| Battery efficiency | Best | Good | Load dependent | Load dependent |
| Works when away | Yes | Yes | No | Yes |
| Starting price | From £495 | From £995 | From £1,495 | From £1,495 |
EPS capability is standard on hybrid inverters but absent from string inverters. All four configuration types above require a hybrid or AC-coupled battery inverter with EPS output terminals. The GivEnergy Gen 1 All-in-One (6kW and 3.6kW models) has none: it backs up the whole house through a Giv-Gateway, or not at all. On Fox ESS the EPS maximum depends on the model: see the limits by model.
GivEnergy: Gen 1, Gen 2 and Gen 3 hybrids, AC 3.0
Sunsynk: Sunsynk Hybrid 3.6, 5.5, 8.0 kW
Growatt: SPH 3000–6000TL3, SPA series
SolaX: X1 Hybrid G4, X3 Hybrid G4
Fox ESS: H1, H3 and KH hybrids, AC-coupled AC1 and AC3, and EVO all-in-ones
Lux Power: SNA / LXP hybrid series
Sigenergy: SigenStor series
Alpha ESS: SMILE5, STORION series
SMA Sunny Boy: (standard, non-Storage series)
Fronius Symo: (non-hybrid series)
SolarEdge: (single-phase without backup interface)
Solis string: (non-hybrid models)
Huawei SUN2000: (without backup LUNA unit)
Most pre-2018 string inverters
Not sure about your model? Check your inverter's datasheet or user manual for an EPS or backup output. If it has none, your inverter does not support EPS. A portal with no EPS option proves nothing: on Fox ESS the setting is in the inverter's own settings. The alternative is inverter replacement with an EPS-capable hybrid model.
Getting the neutral-earth reference right matters in every configuration: exactly one, made only in island mode.
When the grid is live, your home's neutral-earth link comes from the electricity network. When the grid drops and EPS takes over, the output is cut off from that link. Without a replacement reference, RCDs on the EPS circuits cannot be relied on to disconnect an earth fault.
The island needs exactly one neutral-earth reference, made only while islanded. Where the inverter makes its own, that is the one: GivEnergy's hybrids do, and GivEnergy's EPS guide says an external relay is not required. On the Fox ESS H1-G2 the inverter makes the bond and no relay is fitted, and that is why only the G2 version of the H1 works with Fox's EPS box. Otherwise it is a switched relay interlocked with the changeover. It is never a permanent link: that would add a second neutral-earth link while the grid is on, and on a GivEnergy hybrid it would double the inverter's own reference in island mode. Every EPS installation we carry out is tested to confirm a single neutral-earth reference in island mode, and no extra one when grid-connected.
If your EPS was installed by someone else and trips during outages: The neutral-earth reference is one of the first things to check, along with the EPS wiring and settings. See our GivEnergy EPS not working or Fox ESS EPS not working guide for brand-specific troubleshooting.
Regardless of which configuration you choose, the installation follows the same fundamental steps. The complexity and duration increase with more comprehensive configurations.
Before any work begins, we confirm the inverter model supports EPS and that your battery has sufficient usable capacity (minimum 5 kWh recommended for dedicated circuits, 10 kWh+ recommended for full-house changeover). We agree a battery reserve with you, so capacity is held back for EPS use.
We assess your property, existing consumer unit layout, inverter location, and which circuits you want protected to recommend the most appropriate of the four configuration types. For most homes, a dedicated EPS circuit (Type 2) gives the best balance of coverage and battery life. If you want full-house protection, we discuss the trade-offs of manual vs. automatic changeover.
The physical installation is notifiable electrical work and must be done by a Part P registered electrician. For a dedicated circuit, this means a new EPS sub-board with selected circuits transferred. For a changeover switch, the switch is installed between the meter and the main consumer unit. On Fox ESS systems the switching part is an external EPS contactor or one of Fox's own boxes: the EPS BOX-SP on the single-phase H1-G2, KH and EVO, and the EPS BOX PRO-HC-G2 on three-phase. Every configuration is checked for a single neutral-earth reference in island mode. Work is typically completed in half a day for dedicated circuits, or a full day for changeover switch installations.
We enable EPS mode in your inverter's settings. The exact path varies by brand: on GivEnergy it is System Mode Settings → EPS Enable; on Sunsynk it is under Advanced Settings → Off-Grid/EPS; on Growatt, look in System Parameters → Off-grid Settings; on SolaX, it is under Settings → EPS Mode; on Fox ESS it is EPS ON/OFF in the inverter's own settings, and it is off by default on the H1-G2. We also configure the minimum battery reserve for EPS.
With the battery charged, we temporarily disconnect the main AC supply to simulate a grid outage. The EPS circuits should pick up on their own; on GivEnergy hybrid and AC-coupled systems that takes about a second. We test with actual loads, such as lights and appliances, and verify stable voltage and frequency on the inverter display. For changeover switches, we test the full switchover sequence. Grid reconnection is then tested to confirm automatic return to normal operation.
Pricing depends on which configuration type you need. All prices include labour, materials, island-mode earthing checks, inverter configuration, load testing, and a written post-installation report.
EPS wall socket (from £495) or dedicated EPS sub-board (from £995). Both include cabling from inverter EPS terminals, island-mode earthing checks, circuit transfers, configuration, and test.
Manual changeover switch between meter and consumer unit, island-mode earthing checks, EPS wiring, configuration, and full test sequence.
Automatic transfer switch (ATS), changeover wiring, island-mode earthing checks, EPS configuration, and comprehensive test sequence.
All costs confirmed in writing before work begins. EPS wiring is notifiable electrical work and must be done by a Part P registered electrician. We include a post-installation report documenting the EPS circuit layout, changeover switch type, configuration settings, and test results. You receive a clear record of what was done and how to use your EPS system.
Inverter does not support EPS? If your current inverter is a string model without EPS capability, the first step is inverter replacement with an EPS-capable hybrid. We can quote the full job — inverter replacement plus EPS installation — as a single package.
EPS duration depends on battery capacity, protected load, time of day, and battery reserve settings. With a dedicated EPS circuit protecting only essentials, a modest battery can last a full day or more. With full-house changeover, duration drops significantly unless you manage your loads.
If the outage happens in daylight and your panels feed a hybrid inverter, the battery keeps recharging while they generate, which can extend EPS duration at low loads. A GivEnergy AC 3.0 does not charge from solar during a power cut, so plan its runtime on the battery alone. Fox's AC-coupled AC1 and AC3 have no PV input of their own.
Estimates assume 80% usable capacity with 20% battery reserve. On a hybrid inverter, daytime solar extends EPS duration significantly as the panels recharge the battery (not on a GivEnergy AC 3.0, and Fox's AC-coupled AC1 and AC3 have no PV input of their own). Hours shown are approximate and depend on battery health and actual load. Full-house changeover installations should size their load expectations accordingly — see how battery storage works for more detail.
EPS-capable inverter but circuits go dark in a power cut: wiring, EPS settings and island-mode earthing.
See GivEnergy EPS not working →No backup from a Fox ESS system in a power cut: wiring, reserve settings, load limits by model and who fixes what.
See Fox ESS EPS not working →The neutral-earth reference on the All-in-One + Giv-Gateway: what must happen, what changed in 2024, and what we test in island mode.
See GivEnergy Gateway earthing →Extending battery capacity increases EPS runtime. Understand what adding a second module involves and how it improves backup duration.
See adding an extra battery →If your current inverter does not support EPS, replacement with a hybrid model may be the only route to backup power.
See inverter replacement →Understand how solar batteries charge, discharge, and interact with the grid — essential background for sizing your EPS setup.
See how battery storage works →We install EPS backup systems on-site across a wide coverage area from our Yorkshire base — including Leeds, Bradford, Wakefield, Harrogate, York, Sheffield, Huddersfield, Doncaster, Hull, Barnsley, Scunthorpe, Grimsby, Mansfield, Derby, Nottingham, Manchester, Darlington, and Middlesbrough. We also cover Cardiff in South Wales, where STS has a locally-based engineer — same-day to next-day on site.
Whether you want a single EPS socket, a dedicated circuit protecting your essentials, or full-house changeover for complete coverage — we assess, quote, and install. All work is tested on site and documented in writing.
Due to unprecedented demand we’re currently only carrying out on-site work in Yorkshire, and replies are taking up to 7 days. Remote diagnostics continue for the whole UK as normal.
Every message is read and answered, so please don’t send it twice; that only slows the queue.
We use cookies to measure traffic and ads, sharing limited hashed data with Meta and Google. Decline keeps only essential cookies. Privacy policy