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Tariff configuration · Sunsynk

Sunsynk Not Charging on Cheap Rate — Octopus, Agile, Go and TOU Schedule Fixes

Battery should be charging overnight on Octopus Go/Agile but it's not. This is the most common Sunsynk configuration failure in the UK. BST/GMT clock offset and TOU schedule mismatch account for >80% of cases. We cover every tariff and every fix.
  • Most common Sunsynk complaint
  • Usually a 30-minute configuration fix
  • Octopus Go, Agile, Intelligent, Flux
Not seeing overnight charging on cheap rate?

This diagnostic guide walks through every setting. Most cases are resolved by Step 2 — the BST/GMT clock offset.

Book your free remote diagnosticOctopus tariff guide

We configure Sunsynk for all major UK tariffs remotely in a single session.

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 Warning

Do not open your inverter or interfere with DC cabling. Solar panels produce live DC voltage whenever exposed to light. Always use your DC isolator switch and contact a qualified solar engineer for hands-on fault diagnosis.

Diagnosis steps

6-step diagnostic process

Work through these steps in order. Most cases are resolved by Step 2.

1

Confirm your cheap-rate tariff window from your energy bill

Check your energy supplier's portal or your latest bill for the exact cheap-rate hours. Common windows: Octopus Go 00:30–04:30 (GMT/BST) · Octopus Intelligent 23:00–06:00 plus peak windows · Octopus Flux off-peak 02:00–05:00 · Economy 7 approximately 00:30–07:30 (varies by region). Write these times down exactly — you'll need them for Step 2.

2

Check inverter clock and compare to local time

In SolarMan, go to Device → Information and check the inverter's current clock time. Compare it to your local time right now. If the inverter clock is 1 hour behind (e.g., showing 23:00 when it's actually 00:00 BST), this is the problem. During British Summer Time, many Sunsynk inverters don't auto-adjust the clock. The charge window will fire exactly 1 hour late as a result.

BST/GMT offset is the #1 cause: We find that approximately 80% of Sunsynk cheap-rate charging failures are due to the inverter clock being 1 hour off. It's usually a clock adjustment that happened automatically on your phone and laptop, but not on the Sunsynk.
3

Check Time of Use schedule in SolarMan

Navigate to Device → Settings → Time of Use. Find your charge window and verify the start and end times match your tariff window exactly. Common mistake: if Octopus Go is 00:30–04:30 but SolarMan shows 23:30–03:30, the window is offset by 1 hour. Correct it to 00:30–04:30.

Timezone note: Some Sunsynk installations have windows set to GMT times even during BST, or vice versa. Always use your local current time — not GMT or BST as separate entities. Your local time IS GMT or BST depending on the season.
4

Verify grid charge is enabled for the charge window

In SolarMan, check the grid charge settings (usually Device → Settings → Grid Charge). Confirm that grid charge is set to ON for the charge window. If disabled, the battery will only charge from solar generation, not from cheap-rate electricity. Grid charge must be ON for the system to force charge from the grid.

5

Check charge power target and SoC targets

In Device Settings, find the charge power limit (if set). If too low (e.g., 500W), the battery will charge very slowly during the window — a 5kWh battery might only gain 500Wh in 4 hours. Set charge power to the inverter's rated capacity for maximum charging during the window. Also verify SoC target is high (e.g., 90-100%) and minimum SoC is low (e.g., 10-20%) to allow meaningful charge/discharge cycles.

6

Monitor the next charging cycle and verify with SolarMan data

After making any adjustments, check SolarMan's battery SoC graph the following morning. Look for: battery SoC increasing during your charge window, grid power showing as positive import during the window, and battery reaching your target SoC by the end of the window. If charging still hasn't started, book a remote diagnostic — there may be a secondary issue.

Context

About cheap-rate tariff integration

Octopus Energy grew explosively across the UK from 2020 onwards, and many Sunsynk systems were installed without proper tariff-specific configuration. The combination of BST/GMT clock confusion, unclear SolarMan UI, and inconsistent Time of Use scheduling has created a situation where the majority of Sunsynk owners report that their cheap-rate charging doesn't work reliably. In reality, nearly all of these systems can be fixed in a single 30-minute remote session.

STS is a Sunsynk and Octopus specialist. We've configured hundreds of Sunsynk systems for Octopus Go, Agile, Intelligent, and Flux tariffs. The fix is always the same: correct the clock, verify the TOU window times, enable grid charge, and set appropriate SoC targets.

Most common issues (in order)
1. Inverter clock 1 hour off (BST/GMT changeover)
2. TOU window times offset by 30min–1 hour
3. Grid charge disabled in settings
4. SoC target too high — no headroom to charge
5. Charge power set too low — very slow charging
FAQ

Cheap-rate charging questions

The most common cause is a BST/GMT clock offset. Check the inverter clock in SolarMan — if it's 1 hour behind your local time, that's the problem. Correct it to your current local time. Also verify your Time of Use window in SolarMan matches Octopus Go's window (00:30–04:30) exactly. If both are correct and charging still hasn't started, grid charge may be disabled — enable it in Device Settings.
Octopus Agile prices change every 30 minutes and are published by 4pm each day. The simplest approach is to set a conservative window (e.g., 23:00–05:00) that covers most cheaper periods. For advanced optimization, you can manually update your TOU schedule based on the Agile prices each day. We can configure this remotely as part of our tariff setup service, including setting up multiple windows for different patterns.
Not reliably. Many Sunsynk installations require a manual clock adjustment when clocks change in March and October. If your charge window is consistently 1 hour late (e.g., charging starts at 01:30 instead of 00:30), check the inverter clock in SolarMan and adjust it manually to match your local time. This is the #1 cause of Octopus cheap-rate charging failure and the easiest to fix.
A smart meter isn't strictly required for force-charging during cheap-rate windows with Sunsynk, but it helps your system track import and export accurately. Without a smart meter, you may not see real-time grid consumption data in SolarMan, making it harder to verify that charging is happening at the right times. Your installer or STS can check your metering setup during a diagnostic visit and recommend any upgrades needed for optimal performance.
Book

Octopus cheap-rate not working?

Tell us your tariff and what you're seeing. We'll check your SolarMan data and configure your system to work correctly with your Octopus tariff — most cases are fixed in a single session.

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  • Octopus Go, Agile, Intelligent, Flux specialists

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