Problem diagnosis · Solis

Solis Inverter Grid Overvoltage Fault — Why It Disconnects and How to Fix It

Your Solis inverter shows "Grid Over Voltage" and stops exporting during midday solar peaks. It's not the inverter failing — it's protecting the grid. We explain why this happens, how to configure Volt-Watt response, and when to contact your DNO.

Free remote diagnostic £125 only if we fix it remotely

Understand the fault

Affects S6 and RHI models
Grid quality issue, not inverter fault
Volt-Watt and export limiting solutions

Grid overvoltage disconnecting you?

Recurrent "Grid Over Voltage" faults at solar peak times. We review your SolisCloud data and configure Volt-Watt response to reduce trips.

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Note: This is a grid infrastructure issue. We help you manage it through inverter settings.

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Absolutely brilliant service. Our GivEnergy battery stopped working for no obvious reason. The manufacturers have gone in administration so no aftercare is available. Our installer could not diagnose the problem and gave up. We were at our wits end. A web search came up with Solar Tech Support. In truth, the reviews almost seemed to good to be true. But Ron diagnosed the problem within the hour and fixed it remotely the same day. He explained everything clearly and thoroughly and has offered solutions to other issues we had too. I honestly cannot recommend Ron highly enough. An absolute godsend in the mess that GivEnergy have left behind in their demise. Thank you again for all your help!

Edward Johnson · Jul 2026 Trustpilot

Excellent knowledge and service. Ron responded to my initial query really quickly (same day), and confirmed that he could add extra panels and battery to my existing GivEnergy setup - something I’d been told by other installers wouldn’t be possible. Two weeks later (!), scaffolding was up and Ron and his team were on site to fit the extra 5 panels and two more GivEnergy batteries. I now have a truly optimised system, which has made the most of the south facing roof space I have, without having to start again with new kit. I’m now generating enough on the solar to fill my batteries, and avoid using the grid. I’ve also exported far more than before. Brilliant experience, well recommended.

Mark Emery · Jul 2026 Google

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

Fantastic support. We have a Givenergy system where one of our batteries was not working. Ronald successfully helped us get it back up. His perseverance was amazing….and it shows what REAL customer service means. Can’t thank you enough Ron!

Martin · Aug 2026 Google

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

Richard Rodgers · Aug 2026 Google

Wow... a firmware update to my inverter sent the whole system into meltdown – the battery discharged, and the house seemed to be drawing power, and the solar, who knows where that was going? Aghhh... A short email exchange with Roland and Solar Tech Support sorted the problem... the firmware had reversed a setting (from when it was installed), and the CT clamp needed to be reversed. As soon as I had done that, the world returned to normal. Thanks, Roland; there is no way I would have come to that conclusion. Would I recommend them? You bet! Worth the fee? You bet, again!

Pete Hawkins · Jul 2026 Google

Edward Johnson · Jul 2026 Trustpilot

Mark Emery · Jul 2026 Google

Andy Thomas · Apr 2026 Trustpilot

Pete Hawkins · Jul 2026 Google

Written by Ronald · Independent Solar Engineer Last updated 10 November 2026

Important: Grid overvoltage is not an inverter fault — it's a protection. When many solar systems export simultaneously, they raise local grid voltage above safe limits. Your Solis is doing exactly what it should do: disconnecting to protect the network. We help you reduce the frequency of disconnections without sacrificing safety.

Diagnostics

6-step guide to managing grid overvoltage

This is a grid quality issue, not an inverter failure. Follow these steps to understand, monitor, and mitigate the problem.

Check SolisCloud for voltage readings at disconnect time

Log into SolisCloud (soliscloud.com). Navigate to the Event Log or Historical Data section. Find the timestamp when the "Grid Over Voltage" fault was recorded. Click into that event and note:

• Peak AC voltage at the moment of disconnect (should be above 253V)

• Time of day when it occurred (note if it's always at the same time — usually 11am–3pm)

• Duration of disconnect — did it reconnect automatically? How long did it take?

• Export power at that moment — what was the inverter outputting when voltage spiked?

This data tells you whether the overvoltage is transient (occasional spikes) or persistent (sustained high voltage).

Understand G98 voltage limits and confirm consistent overvoltage

Solis inverters follow the G98 grid code, which requires disconnection when:

Under voltage: Below 184V for 2.5 s

Over voltage: Above 262.2 V for 1 s (stage 1) or 273.7 V for 0.5 s (stage 2)

Frequency: Below 47.5Hz for 20 s, below 47.0Hz for 0.5 s, or above 52.0Hz for 0.5 s

In areas with high solar density (many installations on the same street), midday solar export pushes local grid voltage above 253V. This is particularly common in southern England and regions with rapid solar uptake. Check your SolisCloud data:

• Do you see overvoltage events every sunny day? (persistent = local grid issue)

• Do they happen at predictable times (e.g., 12–2pm)? (transient = local export peak)

• Do they clear automatically within 5 minutes? (transient = grid recovers)

Determine if overvoltage is transient or persistent

After a grid overvoltage disconnect, observe the behaviour:

Transient (Clears automatically)

The inverter reconnects within 5–10 minutes. The grid voltage spike was brief and the system recovers naturally.

Action: This is normal grid behaviour. Volt-Watt response will help reduce frequency.

Persistent (Stays disconnected)

The inverter stays disconnected for 30+ minutes. Grid voltage remains above 253V throughout the solar peak period.

Action: Volt-Watt + export limit required. May need DNO involvement.

Note the pattern over 3–5 sunny days. This helps your engineer decide on the best mitigation approach.

Enable Volt-Watt response in SolisCloud settings

Volt-Watt response is a grid support function. When grid voltage rises above a set threshold, the inverter automatically reduces its power output. Lower export = lower voltage rise = fewer disconnections. To enable:

1. Log into SolisCloud and navigate to your inverter settings (usually Inverter → Settings or Advanced Settings).

2. Find "Volt-Watt" or "Volt-Var" response settings (exact naming varies by firmware version).

3. Enable the function and set parameters:

• Volt threshold: 250V (start reducing output before hitting 253V limit)

• Reduction slope: 30–50% power reduction for each volt above threshold

• Example: At 251V, output 70%. At 252V, output 50%. At 253V, output 0%.

4. Save settings and monitor — Check SolisCloud over the next few sunny days to see if overvoltage disconnects reduce.

Volt-Watt typically reduces (but doesn't eliminate) overvoltage events by 50–80%.

Set an export limit to cap peak power output

If Volt-Watt alone doesn't solve the problem, set a maximum export limit. This permanently caps the inverter's output to reduce peak export and keep grid voltage lower. Trade-off: you lose some peak generation, but avoid repeated disconnections.

1. In SolisCloud, find Export Limit or Rated Power settings (usually Advanced Settings → Power Control or Export Settings).

2. Set a limit lower than your system's maximum output. For example:

• 4kW system → set limit to 3kW (25% reduction)

• 5kW system → set limit to 3.5–4kW (20–30% reduction)

3. Monitor voltage impact — Lower export typically reduces peak voltage by 0.5–2V per kW of reduction.

4. Consult your DNO — If persistent overvoltage requires a limit, your DNO may have guidance or requirements.

Export limiting is a permanent trade-off. Use it alongside Volt-Watt for best results.

Verify CT clamp is correctly installed and facing the right direction

The CT (Current Transformer) clamp measures grid import/export. It's used by Volt-Watt and export limiting functions to manage power flow. If installed backwards, the inverter misreads the grid and Volt-Watt/export limiting won't work correctly:

Correct direction: CT clamp arrow points towards the grid (away from your home)

Reversed direction: CT clamp arrow points towards your home — inverter sees export as import and vice versa

Result of reversal: Inverter exports at maximum when it should be limiting, causing worse overvoltage events

Check the main AC cable where the CT clamp is mounted. The clamp should have an arrow printed on its body. Verify it points the correct way. If reversed, your installer or a qualified engineer should correct it — it's a simple physical fix but requires safe access to the main AC wiring.

A reversed CT clamp is one of the most common causes of ineffective Volt-Watt response.

Why grid overvoltage happens — and why it's not a fault

In areas with high solar density (many installations on one street or circuit), simultaneous export from multiple inverters raises local grid voltage. The voltage rise follows Ohm's Law: V = I × R. If 10 homes each export 4kW on a cable with resistance, the cumulative current creates a voltage drop that adds to the base grid voltage. During peak solar periods (11am–3pm), this can exceed the G98 limit of 253V.

This is not an inverter fault — it's a grid infrastructure issue. Your Solis is protecting the network by disconnecting. Protecting the grid prevents damage to transformers and other customers' equipment. The fault code is a safety feature, not a system failure. Managing the problem requires either: (1) reducing export (Volt-Watt/export limit), (2) improving grid infrastructure (DNO action), or (3) accepting occasional disconnections as normal.

Solis S6 and RHI hybrid inverters support Volt-Watt response — a grid support function that reduces output when voltage rises. This is increasingly expected of solar installers as standard practice. In areas with persistent overvoltage, Volt-Watt can reduce disconnect frequency by 50–80%. Export limiting (capping maximum output) provides additional protection but at the cost of peak generation.

Solis grid overvoltage questions

Why does my Solis inverter disconnect at midday even in good weather?

Solis disconnects when grid voltage exceeds 262.2 V for 1 second, or 273.7 V for 0.5 seconds (G98 grid code). On sunny days, multiple solar systems in your area export simultaneously, pushing local voltage above the limit. This is a grid quality issue, not an inverter fault. The inverter is protecting the network. Volt-Watt response and export limiting can reduce the frequency of disconnections.

What is Volt-Watt response on a Solis inverter?

Volt-Watt is a grid support function that automatically reduces inverter output when grid voltage rises. When voltage exceeds a set threshold (typically 250V), the inverter reduces power proportionally — reducing export, which lowers the voltage rise. This helps keep the system below the 253V disconnect limit, reducing trip frequency by 50–80%.

Can the grid overvoltage fault be fixed permanently?

Not permanently by you — it's a grid infrastructure issue affecting your entire area. You can reduce the frequency of disconnections by enabling Volt-Watt response and setting an export limit. If the problem is systematic (many homes affected), contact your DNO — they may upgrade local distribution equipment or lower the voltage set-point. In very high-density solar areas, some disconnections are unavoidable.

How does the CT clamp affect grid overvoltage faults?

The CT clamp measures import/export and is used by Volt-Watt and export limiting to manage power. If installed backwards, the inverter misreads grid flow — it may export when it should limit, causing worse overvoltage events. Verify the CT clamp arrow points towards the grid (away from your home). A reversed clamp is one of the most common causes of ineffective Volt-Watt response.

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Need help managing Solis grid overvoltage?

We review your SolisCloud data and configure Volt-Watt response to reduce disconnection frequency. We'll also verify your CT clamp is correctly installed.

No fix, no fee
SolisCloud data review and optimization
Volt-Watt and export limit configuration

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