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Diagnostic guide · Fox ESS

Fox ESS EPS not working — backup power diagnosis

Power cut but your H1 inverter didn't kick in? The EPS port may not be wired, the battery may have been too low, or the backup circuit is overloading. This guide covers every reason Fox ESS EPS fails and what to check before calling an electrician.
  • H1 and H1-G2 all models
  • Free remote-first diagnostic · no fix, no fee
  • Not affiliated with Fox ESS
EPS didn't activate?

Tell us whether the EPS port is wired, the battery SOC at the time of the power cut, and any alarm codes in Fox Cloud. We diagnose EPS faults remotely.

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Independent — not affiliated with Fox ESS.

5.0
13 Trustpilot reviews
Trustpilot Google

I have a GivEnergy system consisting of two batteries, two inverters and a controlling EMS (Energy Management System) which has not worked since Nov 2025. After six months I discovered Solar Tech Support, reached out to them and Ron phoned me back – how often do you get that service? Could not be more helpful – worked directly with me over the phone, outside what I would call normal working hours. Lucid explanations and we were able to discuss the issues and history using camera and email history. As this was a very rare setup, Ron was able to access an EMS expert in the field to confirm the solution. One sunny day in, I am now only paying for standing charge and a few pence for spikes in grid consumption while battery catches up with house demand.

Ian · May 2026 Trustpilot

When my GivEnergy system had an issue, I was completely left without support and had honestly lost all hope. Thankfully, I searched online and found Ron, which completely turned things around. After sending him a message, he responded incredibly fast and called me to assure me that he would get the problem fixed. I really admire his dedicated, supportive nature and his determination to find a solution. With this kind of outstanding attitude and customer service, he has absolutely secured a future customer in me.

Sree · May 2026 Trustpilot

Ron want out of is way to help, nothing was to much. He was very thorough in what he did Very knowledgeable I would highly recommend Ron and his company He did a fantastic job for me. if you have any problems, he'll do his best to help you out and resolve your problem. I wouldn't hesitate to recommend them

Dennis Brown · May 2026 Trustpilot

Ron took me through a diagnostic to confirm my GivEnergy Inverter had a fault. A common one as it turns out with the AC Inverter. As GivEnergy is defunct there is no immediate fix, aside from sourcing 2nd hand replacement. It may be that a fix becomes available over the summer which would make a lot of GivEnergy customers happy (Again)

Tony Deacon · May 2026 Trustpilot

Contacted Ron with a problem and he sorted it out quickly with no problems at all. Very knowledgeable on anything solar/ batteries. I would recommend him to anyone

Phill · May 2026 Trustpilot

I've spoken to Ron a couple of times with issues with my Givenergy installation. Such a friendly knowledge guy very highly recommended. Thank you very much for resolving my issues

michael fairhurst · May 2026 Trustpilot

Contacted Solar Tech Support in desperation. After explaining the issues I had with my system a diagnosis was made and a solution proposed. Fantastic service, even contacted a manufacturer to arrange replacement parts for me. Great communications, explained all they were doing and what I had to do, clearly and precisly. Followed up to confirm all was ok. Excellent service.

Mr Machin · May 2026 Trustpilot

After GivEnergy went into liquidation, just my luck, my battery started playing up (internal board crashed). Contacted my installer - not interested! Found Solar tech support on a Google search. Sooo glad I found this company! Ron is extremely helpful and has plenty of experience. He soon confirmed what the fault was, and helped me to get my system up and running again. Now moved my GivEnergy account to Solar tech support, and will definitely use again if I have more issues. Unusual to find such a helpful company in these times, no morons reading scripts, just direct contact with the engineer.

Keith Ballard · Apr 2026 Trustpilot

Contacted Solar Tech Support when trying to understand what my Givenergy inverter problem might be and what might be my options. Received good/honest advise which backed up my thoughts.

Hugh Speirs · Apr 2026 Trustpilot

Ron is a super star. Two months ago my GivEnergy battery failed a firmware upgrade leaving it a brick. My installer couldn't/wouldn't fix it. GivEnergy couldn't/wouldn't fix it. Then they went into administration and all hope was lost. A flurry of emails later and Ron had diagnosed the fault (failed USB flash drive, something I'd suspected) and talked me through resolving it. Two months of nothing resolved in about 3 hours. It's great to work with someone who pays attention to the details, knows that they're doing (not just following a script) and gets stuff sorted without a fuss or up-charging.

Christopher · Apr 2026 Trustpilot

I can add to the list of customers who had already 'given up' on GivEnergy due to their appalling customer service, and that was before they went into administration (their Trustpilot reviews don't lie!). So you can imagine my desperation when, having changed my ISP and my Inverter, predictably, proving to be the only device that didn't connect automatically to my new network, I found zero prospect of any customer support with GivEnergy having called in the administrators just five days earlier! The salvation came from Solar Tech Support. My IT advisor stumbled across their web site and some very helpful tips for beleaguered GivEnergy customers, as well as an offer to provide direct assistance. Nothing ventured, I decided to drop them an E-Mail, with very low expectations based on my experience of GivEnergy customer support. Within an hour Ron had responded with some pin point advice, and after a few exchanges of E-Mails he had nailed the problem, enabling the combined efforts of my IT advisor and solar installer to resolve it and reconnect my Inverter. Thank you Solar Tech Support, and Ron in particular, for coming to the aid of a deserted and despondent GivEnergy customer. Expert, razor sharp advice and first class customer service, even though I wasn't officially a customer.

customer · Apr 2026 Trustpilot

This company are a rare gem, I had a very unusual problem following a failed firmware upgrade on my GivEnergy kit. I then found out GivEnergy were in administration and had dismissed all their support staff! None of the usual fixes to try and restore my inverter comms would work, and I looked everywhere, forums, GivEnergy youtube support videos - even AI couldn't figure it out. My installer was talking about huge sums for system replacements, and being vague / evasive about if they'd even install replacement GivEnergy inverter. Enter Solar Tech Support, reassuring and knowledgeable from the very start, I've learnt loads about my solar system though the friendly chat while my engineer worked as he diagnosed the problem and figured out a fix procedure that I've not found anywhere else - amazing . If you need solar system repairs - especially if you like me have been left high and dry by GivEnergy, I cannot recommend this company enough. Give them a call.

Andy Thomas · Apr 2026 Trustpilot

I sent a message on their website regarding a problem I have on my Givenergy system. Although not supplied by Ronald, I thought it was worth an email. Within the hour on a Saturday, he phoned and we discussed the problem. He logged in remotely and gave excellent advice. I'm too far away for his on-site help but he did diagnose the problem and was happy also to chat through my thoughts about an upcoming solar/battery install I'm planning. Great bloke.... if only he was nearer!

Philip · Apr 2026 Trustpilot

I have a GivEnergy system consisting of two batteries, two inverters and a controlling EMS (Energy Management System) which has not worked since Nov 2025. After six months I discovered Solar Tech Support, reached out to them and Ron phoned me back – how often do you get that service? Could not be more helpful – worked directly with me over the phone, outside what I would call normal working hours. Lucid explanations and we were able to discuss the issues and history using camera and email history. As this was a very rare setup, Ron was able to access an EMS expert in the field to confirm the solution. One sunny day in, I am now only paying for standing charge and a few pence for spikes in grid consumption while battery catches up with house demand.

Ian · May 2026 Trustpilot

When my GivEnergy system had an issue, I was completely left without support and had honestly lost all hope. Thankfully, I searched online and found Ron, which completely turned things around. After sending him a message, he responded incredibly fast and called me to assure me that he would get the problem fixed. I really admire his dedicated, supportive nature and his determination to find a solution. With this kind of outstanding attitude and customer service, he has absolutely secured a future customer in me.

Sree · May 2026 Trustpilot

Ron want out of is way to help, nothing was to much. He was very thorough in what he did Very knowledgeable I would highly recommend Ron and his company He did a fantastic job for me. if you have any problems, he'll do his best to help you out and resolve your problem. I wouldn't hesitate to recommend them

Dennis Brown · May 2026 Trustpilot

Ron took me through a diagnostic to confirm my GivEnergy Inverter had a fault. A common one as it turns out with the AC Inverter. As GivEnergy is defunct there is no immediate fix, aside from sourcing 2nd hand replacement. It may be that a fix becomes available over the summer which would make a lot of GivEnergy customers happy (Again)

Tony Deacon · May 2026 Trustpilot

Contacted Ron with a problem and he sorted it out quickly with no problems at all. Very knowledgeable on anything solar/ batteries. I would recommend him to anyone

Phill · May 2026 Trustpilot

I've spoken to Ron a couple of times with issues with my Givenergy installation. Such a friendly knowledge guy very highly recommended. Thank you very much for resolving my issues

michael fairhurst · May 2026 Trustpilot

Contacted Solar Tech Support in desperation. After explaining the issues I had with my system a diagnosis was made and a solution proposed. Fantastic service, even contacted a manufacturer to arrange replacement parts for me. Great communications, explained all they were doing and what I had to do, clearly and precisly. Followed up to confirm all was ok. Excellent service.

Mr Machin · May 2026 Trustpilot

After GivEnergy went into liquidation, just my luck, my battery started playing up (internal board crashed). Contacted my installer - not interested! Found Solar tech support on a Google search. Sooo glad I found this company! Ron is extremely helpful and has plenty of experience. He soon confirmed what the fault was, and helped me to get my system up and running again. Now moved my GivEnergy account to Solar tech support, and will definitely use again if I have more issues. Unusual to find such a helpful company in these times, no morons reading scripts, just direct contact with the engineer.

Keith Ballard · Apr 2026 Trustpilot

Contacted Solar Tech Support when trying to understand what my Givenergy inverter problem might be and what might be my options. Received good/honest advise which backed up my thoughts.

Hugh Speirs · Apr 2026 Trustpilot

Ron is a super star. Two months ago my GivEnergy battery failed a firmware upgrade leaving it a brick. My installer couldn't/wouldn't fix it. GivEnergy couldn't/wouldn't fix it. Then they went into administration and all hope was lost. A flurry of emails later and Ron had diagnosed the fault (failed USB flash drive, something I'd suspected) and talked me through resolving it. Two months of nothing resolved in about 3 hours. It's great to work with someone who pays attention to the details, knows that they're doing (not just following a script) and gets stuff sorted without a fuss or up-charging.

Christopher · Apr 2026 Trustpilot

I can add to the list of customers who had already 'given up' on GivEnergy due to their appalling customer service, and that was before they went into administration (their Trustpilot reviews don't lie!). So you can imagine my desperation when, having changed my ISP and my Inverter, predictably, proving to be the only device that didn't connect automatically to my new network, I found zero prospect of any customer support with GivEnergy having called in the administrators just five days earlier! The salvation came from Solar Tech Support. My IT advisor stumbled across their web site and some very helpful tips for beleaguered GivEnergy customers, as well as an offer to provide direct assistance. Nothing ventured, I decided to drop them an E-Mail, with very low expectations based on my experience of GivEnergy customer support. Within an hour Ron had responded with some pin point advice, and after a few exchanges of E-Mails he had nailed the problem, enabling the combined efforts of my IT advisor and solar installer to resolve it and reconnect my Inverter. Thank you Solar Tech Support, and Ron in particular, for coming to the aid of a deserted and despondent GivEnergy customer. Expert, razor sharp advice and first class customer service, even though I wasn't officially a customer.

customer · Apr 2026 Trustpilot

This company are a rare gem, I had a very unusual problem following a failed firmware upgrade on my GivEnergy kit. I then found out GivEnergy were in administration and had dismissed all their support staff! None of the usual fixes to try and restore my inverter comms would work, and I looked everywhere, forums, GivEnergy youtube support videos - even AI couldn't figure it out. My installer was talking about huge sums for system replacements, and being vague / evasive about if they'd even install replacement GivEnergy inverter. Enter Solar Tech Support, reassuring and knowledgeable from the very start, I've learnt loads about my solar system though the friendly chat while my engineer worked as he diagnosed the problem and figured out a fix procedure that I've not found anywhere else - amazing . If you need solar system repairs - especially if you like me have been left high and dry by GivEnergy, I cannot recommend this company enough. Give them a call.

Andy Thomas · Apr 2026 Trustpilot

I sent a message on their website regarding a problem I have on my Givenergy system. Although not supplied by Ronald, I thought it was worth an email. Within the hour on a Saturday, he phoned and we discussed the problem. He logged in remotely and gave excellent advice. I'm too far away for his on-site help but he did diagnose the problem and was happy also to chat through my thoughts about an upcoming solar/battery install I'm planning. Great bloke.... if only he was nearer!

Philip · Apr 2026 Trustpilot
⚠️
Safety first: EPS diagnosis involves your home's electrical supply. Do not open the consumer unit or modify any wiring yourself. The steps below cover settings and checks you can do in Fox Cloud and at the inverter. Any wiring changes — including adding EPS circuits or neutral-earth bonding — must be carried out by a qualified electrician.
Diagnosis

Step-by-step EPS backup diagnosis

Work through these steps in order. Step 1 catches the majority of cases — the EPS port was never wired during installation.

1
Confirm the EPS port is physically wired

The H1 inverter has a dedicated EPS output port, but it is not always connected during installation. Many UK systems are fitted without the EPS circuit wired — the port is simply left unused. Check with your installer whether the EPS output is connected to a sub-board or changeover switch. If the EPS port is not wired, the inverter cannot supply backup power regardless of any settings in Fox Cloud. Adding EPS wiring after installation is possible but requires a qualified electrician.

2
Check Min SOC and Min SOC (On Grid) settings

In Fox Cloud, check the two minimum SOC settings. Min SOC is the absolute floor — the inverter will never discharge below this point, even during a power cut. Fox ESS recommends 10%. Min SOC (On Grid) is the minimum level during normal grid-connected use. If this is set to 10%, the battery routinely drains to near-empty during evening use, leaving almost nothing for EPS when a power cut occurs. Set Min SOC (On Grid) to 20–30% to ensure a meaningful backup reserve is always available.

3
Consider Backup work mode to hold battery reserve

The Backup work mode in Fox Cloud holds the battery at a high state of charge and only discharges to cover essential loads during a power cut. If you live in an area with frequent outages or need guaranteed backup, switch from Self-Use to Backup mode. In Self-Use, the battery discharges freely during the evening to offset grid import — which means it may be empty when a power cut hits. Backup mode sacrifices some daily savings but ensures the battery is always ready for EPS.

4
Check for overload on the EPS circuit

The H1 EPS output is limited to 3kW to 5kW depending on the model. If the total load on the backup circuit exceeds this, the inverter trips on overload and shuts down EPS output. High-draw appliances — kettles, electric ovens, immersion heaters, electric showers — will almost certainly exceed the EPS capacity. Reduce the load to essentials: lighting, fridge, router, and a few sockets. EPS should recover automatically once the excess load is removed and the grid fails again or a manual test is triggered.

5
Check neutral-earth bonding (RCD tripping on EPS)

The Fox ESS H1 does not create a neutral-earth bond internally when operating in EPS mode. Without this bond, RCDs on the backup sub-board may trip immediately when the grid drops — cutting power to the circuits you are trying to protect. The fix is an external N-E bonding relay that activates automatically when grid power is lost. This is an installation requirement, not a Fox Cloud setting. If your RCDs trip every time EPS activates, this is almost certainly the cause.

6
Test EPS with a simulated power cut

If wiring and settings look correct, test EPS by switching off the main grid supply at your consumer unit. The inverter should detect the grid loss within approximately one second and switch to EPS mode, powering the connected circuits from the battery. Check Fox Cloud for any alarm codes during the test. If EPS still fails to activate, contact STS for a remote diagnostic — the issue may be a firmware fault, a wiring error, or an inverter configuration that needs installer-level access to correct.

Fox ESS EPS backup — what you need to know

EPS stands for Emergency Power Supply. On the Fox ESS H1 hybrid inverter, the EPS port provides battery-backed power to selected circuits during a grid outage. The system detects grid loss and switches to battery power within approximately one second — fast enough for most electronics but not instantaneous. The EPS port must be physically wired to a sub-board or changeover switch during installation for backup to work. Many UK installations leave this port unconnected, which means the inverter and battery are present but the home has no backup capability at all.

For whole-house backup, a changeover switch such as the Fox ESS EPS Box transfers the entire property to inverter power when the grid fails. Without this, only circuits on the dedicated EPS sub-board receive backup. The H1 EPS output is rated between 3kW and 5kW, so high-draw loads must be excluded. The two most common problems STS diagnoses remotely are Min SOC (On Grid) set too low — leaving the battery empty before the power cut happens — and missing neutral-earth bonding, which causes RCDs to trip the moment EPS activates. Both are fixable without replacing any hardware.

FAQ

Fox ESS EPS backup — common questions

The most common reason is that the EPS port on the H1 inverter was never wired during installation. Many UK systems are fitted without the EPS circuit connected, leaving the inverter with no path to deliver backup power. If the port is wired, check the Min SOC (On Grid) setting — if the battery drains to low levels during normal evening use, there may be nothing left when a power cut hits.
EPS requires physical wiring from the inverter's EPS output port to a dedicated sub-board or changeover switch — this must be done by a qualified electrician. Once wired, EPS is enabled in Fox Cloud under inverter settings. Set Min SOC (On Grid) to 20–30% so the battery always holds a reserve. For whole-house backup, a Fox ESS EPS Box or third-party changeover switch is needed. If you need help configuring EPS settings, book a remote diagnostic.
Min SOC is the absolute minimum the battery will ever discharge to — even during a power cut. Fox ESS recommends 10%. Min SOC (On Grid) is the minimum during normal grid-connected use, and this is the key setting for backup reserve. Setting it to 30% means the battery stops discharging at 30% during normal operation but can draw down to the Min SOC level during an actual power cut — giving you the full range between the two values for emergency use.
It depends on the wiring and total load. By default, the EPS port only supplies a dedicated sub-board with selected circuits. For whole-house backup, you need a changeover switch such as the Fox ESS EPS Box. Even with whole-house backup, the H1 EPS output is limited to 3–5kW, so high-draw appliances like electric showers and ovens will overload the system and should be excluded from the backup circuit.
The H1 inverter does not create a neutral-earth bond internally when in EPS mode. Without this bond, RCDs cannot detect fault current correctly and trip immediately. The solution is an external N-E bonding relay that activates when grid power is lost — this is a wiring modification by a qualified electrician. It's a known requirement for Fox ESS EPS installations, not a fault. If you're unsure whether your installation has this, contact STS for a remote assessment.
Book

EPS still not activating?

Tell us whether the EPS port is wired, the battery SOC when the power cut happened, and any alarm codes in Fox Cloud. We diagnose Fox ESS backup faults remotely using installer-level portal access. Independent from Fox ESS and your installer.

  • Not affiliated with Fox ESS
  • Free remote diagnostic · no fix, no fee
  • On-site visits available across the UK

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