Triad

The Triad mechanism was the historical method for recovering transmission network costs from large UK electricity customers. Under it, the system operator identified the three half-hour settlement periods in each November-to-February window that carried the highest national demand — separated by at least ten clear days — and used those three periods as the reference for calculating each large customer's share of TNUoS for the following year.

The economic effect was a powerful incentive for large customers to forecast and avoid demand during likely Triad periods. An entire industry of "Triad warning" services grew up to predict the periods and trigger demand reduction (battery discharge, on-site generation, load shifting) during the warning windows.

Following the Targeted Charging Review (TCR), the residual element of TNUoS is now recovered through fixed bands based on a customer's historic agreed capacity and net consumption volume. The Triad-avoidance incentive on the residual element has therefore been removed: avoiding peak demand no longer reduces your TNUoS bill on the residual element. The forward-looking, locational element of TNUoS — much smaller in cost terms — does still carry a time-of-day signal, so some peak-period management retains value, but it is far less material than under the original Triad mechanism.