Curtailment information

Curtailment information

We have introduced a new curtailment forecast and index for flexible connections, providing a better service to connections customers.


What is curtailment?

Curtailment in electricity connections refers to the deliberate reduction or limitation of electricity generation or consumption during certain periods. This is done to balance the supply and demand of electricity on the power grid.

We recognise the potential impact unexpected import and export curtailment can have on our flexible connections customers. We want to give you a clear view of average interruptions you could experience, but also commit to safeguarding your operations from excessive curtailment.  In this way, we look to help customers complete revenue modelling and make more informed investment decisions.

Our curtailment forecast, indicating expected interruptions, curtailment index and demonstrating our commitment to you, will be offered to all new flexible connection customers receiving new formal connection offers or connection agreements on or after 4 December 2017.


Once connected, we will review actual curtailment your site has experienced and share this information with you annually. We will gather data on your site’s curtailment via a remote terminal unit (RTU) and planned outage schedules.

How would it work in practice?

Take a look at our High Voltage scenario example.

Download here


What information will I receive annually?

At the end of the first full financial year following connection energisation or commissioning of the RTU, whichever of the two is completed last, the first letter will be issued. This letter will outline the actual curtailment in that year and state the average within the defined six year period.

If the actual curtailment exceeds the index defined within the connection agreement, we will investigate and develop a range of options to bring curtailment back beneath the index. While development and review of a solution once the index has been reached is guaranteed, its progress will be subject to associated regulatory investment criteria to ensure the most efficient solution.


How do we calculate our forecasts and index?

We will consider scenarios when the system is abnormal and unavailable, for instance during faults, construction outages and maintenance outages to determine the ‘actual’ and forecast curtailment. The index is then derived from the forecast and forms the trigger point for us to seek to intervene.

In your annual review letter, we will provide the ‘actual curtailment’ experienced, looking back over the year. We calculate the ‘actual’ curtailment in the first six years using a simplistic average. In subsequent years (from year seven onwards), we will calculate the actual curtailment using data we’ve collected in the first previous six years, on a rolling basis.

Curtailed Connection Offers

From 1st April 2023, Curtailed Connection Offers are available for new applications for connection to our network where reinforcement is identified as necessary to facilitate the connection, and where there is an option to curtail the import and/or export of the connection to manage any constraint on the distribution network until the necessary reinforcement is completed.

The benefit of a Curtailed Connection Offer is that it may facilitate an earlier energisation date by restricting the available import/export at certain time periods or periods of the year. The amount of curtailment that the connection will be subject to will be expressed in total hours across a year, for example 4,000 hours out of the 8,760, or 45% curtailment, in one year.

After receiving a Curtailed Connection Offer and accepting it, we will conduct a more thorough evaluation to determine the exact number of curtailment hours. During these hours, we will compensate you at a predetermined fixed price.  This price would be payable for every additional hour that your site was curtailed above the figures provided.

A Curtailed Connection Offer can only be made where a formal connection offer is requested. It cannot be provided for a budget or gen plus quote.

For every official application that requires distribution reinforcement, we will offer a Curtailed Connection Offer. However, the offer for curtailment options will only be provided if the specified conditions in the guidance below are met.

  • Reinforcement is a requirement to provide a connection for the application, in accordance with the Minimum Scheme
  • The identified reinforcement is not to mitigate against a fault level constraint
  • A curtailed alternative is achievable prior to the completion of the reinforcement
  • The site is able to be constrained with the existing distribution network management system
  • The application is not deemed to be for a ‘small customer’*

*A “small customer” is either a domestic or non-domestic customer who are whole current metered ie up to 20kVA for 1ph and 60kVA for 3ph. A “small customer” generally excludes those who do not have a current transformer (“CT”) meter.

It is important to note that for applications where reinforcement of the transmission network is required, a Curtailed Connection Offer may not be appropriate. No capacity may be energised prior to the given consent date from National Grid, which is certain instances may be after the Distribution Reinforcement is completed.

Further information is available here in this ENA webinar on Curtailed Connection Offers.

If you would like to contact us about anything concerning curtailed connection offers, please email

Still unsure?

If you still have any questions please speak to your connections engineer or email the contracts team.

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