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.
Recurrent "Grid Over Voltage" faults at solar peak times. We review your SolisCloud data and configure Volt-Watt response to reduce trips.
Book Remote Diagnostic — from £75 → Back to Solis hubNote: This is a grid infrastructure issue. We help you manage it through inverter settings.
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.
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:
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:
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:
Determine if overvoltage is transient or persistent
After a grid overvoltage disconnect, observe the behaviour:
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.
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:
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.
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:
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
Solis disconnects when grid voltage exceeds 253V for more than 200ms (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.
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%.
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 raise the voltage set-point. In very high-density solar areas, some disconnections are unavoidable.
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.
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.
Return to the Solis brand hub to explore other common faults and services.
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