Learn why the Triads we’re familiar with have ended and how electricity bills have changed following Ofgem’s Targeting Charging Review (TCR), covering transmission and distribution network costs.
What impact did Triads have on major power users?
Triads were three half-hour, peak periods during the winter that saw the highest demand for electricity. “Tri” refers to the three periods, while “AD” stands for average demand.
Triads could have been on any day from 1 November to the end of February, but they had to be at least 10 days apart so that they didn’t fall on consecutive days.
Triads usually occurred between 5pm and 6pm because that’s when both industrial and domestic consumption tended to peak. But they did sometimes occur outside this window.
If you get half-hourly bills, your total Transmission Network Use of System (TNUoS) charge for the coming financial year used to be calculated based on your average consumption in the three half-hour Triad periods.
So if you’re a heavy user of electricity, optimising these costs could have made a big difference to your annual spend – the more you reduced your energy usage during Triads, the lower your TNUoS payments would have been for the whole of the next year.
Why is Triad avoidance no longer valuable?
Since Triad-based charging was introduced in the 1990s, experts grew ever more skilled in predicting when Triads were likely to occur, and helping customers reduce their electricity consumption from the grid during these times.
This avoidance meant that network users who couldn’t turn down their consumption at these times faced a larger share of paying to cover system maintenance and upgrades. Ofgem began its TCR in 2019 to address this imbalance.
Since April 2023, following TCR, the TNUoS residual charge has changed to a fixed £/site/day charge, varying by meter type and band, so it’s no longer determined by Triads. The Triad element of the TNUoS charge has been reduced to zero in many areas.
That means there's now minimal cost benefit from load shifting to avoid using power at peak times.
How has charging changed?
Since 1 April 2023, Transmission Network Use of System (TNUoS) charges have been set according to a site’s charging band, which is based on Authorised Supply Capacity (KVa) and allocated by the local Distribution Network Operator (DNO). Many areas now pay nil triad, as TNUoS has become part of the standing charge.
Distribution Use of System (DUoS) also changed from April 2022, increasing fixed daily charges and reducing volume-based charges.