Review of Transmission Network Use of System (TNUoS) charges and Triads

Review of Transmission Network Use of System (TNUoS) charges and Triads

The Triad charges collect the revenue for the management of the Electricity Transmission system, known as the Transmission Network Use of System (TNUoS). This cost makes up in the region of 7% of an Electricity bill, but it can vary significantly depending on specifics. An obvious example of Transmission is the long-distance movement of Electricity through overhead pylons.

Triads consist of the three peak periods of national consumption, identified in March, but based on the previous November to February figures, Monday to Friday. Because it’s retrospective, for Half Hourly meters the energy supplier will, where contractually possible, use Half Hourly (HH) data to perform a reconciliation, to invoice the difference between what they estimated and the actual charge. Suppliers also use this information to calculate future fixed priced contracts.

Looking at the last ten years, typically Triads have fallen on a Monday (43%) or a Thursday (27%) and most commonly between 17:00 and 17:30 (67%). Some customers with HH meters use Triad Alerts offered by energy suppliers and Indigo Swan to forecast when a Triad is likely, and where possible reduce their usage, to lower the Triad charge.

From April 2023 as part of the Targeted Charging Review, Electricity meters were placed into bands based on, the level of consumption for NHH meters and for HH meters, the Available Capacity kVA and voltage. The review’s aim is for a fairer and more transparent way of collecting industry costs. It also looked at Balancing and Distribution charges, which have also seen changes.

Generally, for those customers in the north and Scotland, the national bands will replace Triads, whereas for those in the south, bands will recover about 90-95%. The remaining 5-10% will continue to be through Triads. The new band charge will be in the form of a fixed £/day. This means that there is a reduced incentive to avoid Triads and a greater emphasis on lowering energy use and the Maximum Demand kVA spikes and ultimately, the Available Capacity kVA.

Each HH meter’s Available Capacity for the bands was established during the period October 2018 to September 2020. With this being the key to charges for HH meters going forwards, it is another reason to make sure that the level is appropriate for the site. Any request to reduce the band due to the reduction of the Available Capacity is likely to be rejected unless it is by over 50%. Updates to the bandings are due to be from April 2026.

Should you wish Indigo Swan to carry out a review of your HH meter’s Available Capacity, please get in touch.

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