Ofgem UK Domestic Electricity Grid Scandal

By S Collins Chartered Electrical Engineer C.Eng. MIET.

Do you have defective LED lights that don’t last the stated hours or unable to fully export solar power to the grid then it’s likely an issue of overvoltage in your electrical supply an ever-increasing problem.

The rapid increased in the provision of solar generation is highlighting that the DNO’s have failed to adjust the voltage of the network, to average of 230v standard as not often thought of as 240v.  Most people do not have the tools to measure the network voltage overtime, but solar Inverters being increasingly installed, have the ability to continuously monitor the grid supply. If you look in the statistics of “Grid Voltage” then a general solar owner can see the state of the electric network and the average and peaks. Significantly more people are complaining, when the realise that they are not exporting the expected energy due to limitation in output by the DNO.

Ofgem have failed to deal with this issue.  You ask the industry why! and you get the same response. “We never changed the network to an average of 230v”. After 20 years since the change in the UK Electrical standards in January 2003, there has been no action by the DNO’s or Ofgem.  Why is Ofgem not making the DNO’s, comply with the regulation of 230v average voltage (-6% / +10%), instead the average in the UK is around 243v-246v. Ofgem focuses on customer service issues and cost but has totally failed to deal with the underlying issues of the network safety and security.

In my own case, I see overvoltage peaks nearly every day with periods of 251v-253v and up to 259v between 10:00 – 16:00. Yes, I have reported the issue and my DNO (SSEN) and they should reduce the voltage taps by at least 6V or better 12V to manage the overvoltage. The issue is that Ofgem consider this not a serious issue, and allow DNO’s 6 months to respond to this type of issue. This puts people at a financial loss, the UK with a greater carbon release, as we are unable to harness the existing solar energy supply, as well as some safety risks.

The standards used for domestic facing generation equipment such as solar inverters must stop exporting if the grid reaches 253v. So, on a sunny day and all your neighbours are   exporting solar the grid voltage tries to go above the already high average voltage level and the inverters start to shut down, as there is not the designed margin level in the network.

So much for the green revolution, you get lots of sun and you export even less than when its cloudy, I have seen this myself with a good spring, meeting my predicted solar, as summer came along a big loss in solar generation.

Does this only affect the lucky people that can export solar: No, we are all affected.

Our energy costs for domestic consumers are largely now devices that use low volage supplies that are converted with power supplies units, and these consume and waste more, with an increased voltage supply.

Most domestic devices are designed to meet the EU agreed standards that is 220V and so many manufacture’s use components in their devices that are at a limit of 240v for both the UK and EU. This is fine if we had an average UK voltage at the specified 230v, but we don’t; so, for example capacitor-based voltage droppers in LED lights have a rapid decrease of life due to overvoltage and in a small number of cases can cause fires in the lights. This issue is replicated though out the home in all the other devices as they all have smart low voltage components, more often than not with capacitive based voltage dropping circuits.

So why has the issue of overvoltage not been managed better. To some extent, greed by the DNO as it costs them money to alter the network and, in some case, they have to replace of very old equipment; so, reducing profit. They have though had 20 years to act and so it should not be an issue.

Ofgem on the other hand have no excuse, and have failed in particular the domestic user, in the lack of control over the state of the electric distribution network, and being fit for purpose for de-carbonising of the energy supply and increase in Microgeneration around the network. They failed to carry out any independent monitoring of Conformance, Surveillance and Safety of the network to the agreed standards, but rely of the network operator to report to them, on various customer facing metrics, but this does not cover Non-compliance of the Voltage of the Distribution network such as overvoltage issues, and fails to publish statistic on the issue.

We urgently need Ofgem to carry out its duty to act as an effective regulator and ensure that the DNO act quickly to stop the over-voltage issues (days not months) and to rapidly reduce the whole of the UK Domestic Network to an average of 230v thereby:

  • Ensuring that all microgeneration system can supply the grid at full power and we minimise the use of fossil fuels
  • Improve the efficiency of the domestic supplies by reducing the increased loss due to a high voltage in the network.
  • Improve safety as the domestic devices will not be over stressed due to voltage excess.
  • Provide assurance to the consumers that the DNOs are taking seriously the role to minimise the network losses and maximise the microgeneration by residential customers and demonstrate that they are monitoring and acting quickly in resolving network compliance.
  • Ofgem needs to publish statistics for over-voltage and network performance, that monitor the actions of the DNO not just rely on their statistic. In addition, it should have its own monitoring program, similar to other regulators such as Ofcom that use external organisations to monitor the performance and compliance of operators.
  • Set a code of conduct on DNO’s to make them resolve over-voltage issues within less than 30 days, and if not compensate users for the loss of damaged caused.

This issue is critical, and needs Ofgem to urgently act to correct its mistakes in both surveillance and regulation of the supply network, to ensure the network is safe and effective for now and future.


The Distribution Network Operators (DNOs) who are licensed companies that own and operate the infrastructure and meters that carry electricity from the national transmission system and distribute it throughout Britain.


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