If you're dealing with a fault related to this topic, a remote diagnostic identifies the root cause and recommends the fix — usually within 30 minutes. All major brands supported.
Book your free diagnosticHow diagnostics workFive stars for Ronald at Solar Tech Support. It’s been stressful trying to figure things out since GivEnergy went under, but Ronald was a welcome relief. He was incredibly knowledgeable about the system and sorted me out with some excellent advice. Really glad I found this service and will be keeping them on speed-dial for any issues in the future!
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.
Ron made more sense in 20 mins than our installer has done over the last 12 months There is a jungle out there and you need someone like Ron to give a comprehensive overview and solution
We were having problems with our inverter, couldn’t get an early response from our installer a stressed conversation between our installer and solar tech support led to a text to us to authorise connection to your company . Ron was a very helpful and knowledgeable man who tried with a bit of difficulty as we are pensioners and very knowledgeable. Spent time on phone without making us feel small.we would recommend this company if you have any problems. Thanks Ron 5 star
Absolute legend found the fault in 5mins definitely will be using again definitely would recommend to others .
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!
An export limit is a cap on how much electricity your solar system is allowed to send back to the grid. It exists because the local distribution grid was not designed with large amounts of distributed generation in mind — and exporting too much power can cause voltage rise issues for neighbouring properties and grid equipment.
The DNO is the company responsible for the electricity cables and transformers in your area — not your energy supplier, and not Ofgem. There are six main DNOs in Great Britain: National Grid Electricity Distribution (NGED), SP Energy Networks, Electricity North West, Northern Powergrid, UK Power Networks, and Scottish Hydro Electric Power Distribution.
When your installer applies to connect your solar panels to the grid, the DNO assesses how much export capacity is available on your local feeder. They issue an approval letter specifying your permitted maximum export.
Most domestic systems fall into one of these categories:
Zero export is more common on older rural and suburban feeders with less headroom. Newer grid reinforcement schemes and smart export limitation programmes are gradually increasing available capacity.
When generation exceeds the export limit plus household consumption, the inverter enters curtailment mode. It actively reduces the amount of power the panels are producing (by adjusting its MPPT tracking point) to prevent export exceeding the permitted level.
G98 and G99 are the Engineering Recommendations that govern how small generators connect to the UK low-voltage distribution network. Your installation will fall under one of these, and the letters from your DNO reference whichever applies.
Used for small generators. No prior approval needed — the installer simply notifies the DNO within 28 days of connection.
Installations with a total inverter output up to 3.68 kW on a single-phase supply use G98. Anything bigger is always G99, even with export limited: a 5 kW inverter limited to 3.68 kW is still G99, never G98.
Used for larger generators or constrained network areas. Requires formal DNO application and approval before connection.
G99 approval letters frequently include conditions: a specific export limit (e.g. 2 kW), reactive power control, or requirements for Smart Export Limitation equipment.
Check the paperwork your installer provided at handover. If you received a G98 notification acknowledgement, your system is G98. If you received a formal G99 approval letter with conditions, it is G99. If you are not sure, your installer is legally required to have kept records — contact them with your installation address.
Export limitation is an active, real-time control loop inside your inverter. It is not a one-time setting — the inverter constantly adjusts to keep export below the configured cap. Here is how the loop works.
A CT clamp (current transformer) is installed on the main cable between your electricity meter and consumer unit. It measures, in real time, how much power is flowing into your property (import) and out to the grid (export). This signal is sent to the inverter continuously — typically updated every few seconds.
Without the CT clamp, the inverter has no way of knowing whether power is leaving your property or being consumed on-site. The CT clamp is essential to export limiting — the two cannot be separated.
The export limit value is programmed into the inverter during installation (in watts or kilowatts). Every few seconds, the inverter compares the live CT clamp reading to this value.
When a battery is present, the inverter must account for battery charge/discharge when calculating available export headroom. A correctly configured system will:
Misconfigured systems can apply the export limit as a total output cap, preventing the battery from operating correctly. If your battery is not charging or discharging as expected and you have an export limit set, check the inverter event log for export limit interactions.
There is always a small lag between the CT clamp reading and the inverter's response — typically 0.5–2 seconds. During this window, export can briefly exceed the limit by a small amount. This is normal and expected. However, if the inverter's control loop is over-aggressive, it may overshoot in the other direction and suppress generation far more than needed.
Over-curtailment symptoms: generation appears to plateau well below expected on sunny days; portal shows frequent small curtailment events even at low output. This is often caused by a reversed or poorly positioned CT clamp giving the inverter inaccurate readings.
Zero export is the strictest form of export limitation: the inverter must maintain export at exactly 0 W at all times. No power from your solar panels or battery is allowed to reach the grid.
The inverter continuously monitors the grid CT clamp and curtails generation the moment export approaches zero. Because there is always a small CT clamp response lag, the system typically targets a small buffer below zero (e.g. maintaining a slight import of 50–100 W) to prevent accidental export. This is why zero export systems occasionally appear to waste a small amount of generation — the buffer is intentional.
Yes — significantly. Without a battery, excess solar generation that exceeds house consumption is simply curtailed (wasted). With a battery, excess solar charges the battery instead of being curtailed. The inverter prioritises battery charging over curtailment, so generation that would otherwise be lost is stored and used later.
Not all zero-export systems have a DNO requirement for zero export. Some installers set the export limit to 0 W by default — either as a conservative commissioning choice or because the customer asked for it (e.g. to avoid SEG admin). If your system is zero export but you have no G99 condition requiring it, you may be able to increase the limit to what your G98 notification or G99 approval allows.
Before changing any setting, confirm your DNO approval allows export. Check the letter, not the installer's memory. If you are unsure, see the export limit issues diagnosis guide or contact the DNO directly.
Export limiting depends entirely on accurate CT clamp data. If the CT clamp is reversed, in the wrong position, or disconnected, the export limiting system cannot work correctly — and neither can self-consumption optimisation or battery charging.
A reversed CT clamp means the inverter thinks power is flowing in the opposite direction to reality. With export limiting enabled, this causes the system to believe it is exporting when it is actually importing (and vice versa).
A reversed CT clamp must be physically flipped — it cannot be corrected in software on most inverters. See the CT clamps guide for how to confirm and report the fault.
The export-limiting CT must be on the main grid connection cable — the cable between the electricity meter and the main distribution board. If it has been installed on a sub-circuit (e.g. only the solar output cable), it measures generation rather than net export and will not enforce the limit correctly.
This is more common on retrofit installs where the installer chose a convenient cable rather than the correct measurement point. It can look like the system is working normally but the export limit is not being enforced.
A loose CT clamp connector or physically damaged clamp will produce intermittent or zero readings. Without CT data, most inverters default to a safe state: either stopping export entirely (zero export fallback) or disabling export limiting entirely depending on the brand.
The answer depends on where the limit came from. There are two distinct situations: a limit set by the DNO as a grid connection condition, and a limit set by the installer in the inverter settings independently of the DNO. Only the second type is easily changeable.
Specified in your G99 approval letter as a condition of connection. Cannot be changed without DNO consent.
Set in the inverter settings independently, often lower than the DNO approval actually allows.
Some DNOs offer Smart Export Limitation as an alternative to a fixed low export cap. SEL uses a direct communication link (usually a broadband connection to the inverter or gateway) to send a dynamic export limit signal from the DNO to your system. On most days the limit is unrestricted; during network stress periods the DNO can reduce export remotely and temporarily. This allows higher average export than a fixed conservative cap while protecting the network during peak periods.
SEL is more common in Scotland and Wales where rural networks have limited headroom. Not all inverter brands support it — GivEnergy and Solis have developed compatible firmware. If your DNO has offered SEL, ask your installer to confirm whether your inverter supports it.
How CT clamps work, why direction matters, and how to perform the kettle test.
See CT Clamps Explained →Battery chemistry, charge/discharge cycles, and how zero-export mode interacts with storage.
See How Battery Storage Works →Step-by-step diagnosis if your inverter is actively curtailing more than expected.
See Export Limit Issues →How to confirm a reversed or mispositioned CT clamp and what to do about it.
See CT Clamp Installed Wrong →What your installer should have confirmed and handed over, including export limit paperwork.
See Installation Day Checklist →Which connection standard applies to your system, Fast Track G99, and what to do if DNO registration is missing.
See G98 vs G99 Explained →If your system is curtailing more than expected, your CT clamp readings look wrong, or you are not sure what your DNO approval actually permits, a remote diagnostic session reviews your portal data and inverter settings to find the cause — usually within 30 minutes.
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