The National Grid identifies three “Triad periods” every year between November and February which are used to calculate the Transmission Network Use of System (TNUoS) charges for all Half-Hourly Metered customers.

A Triad is one of the three highest half-hour periods of national electricity use demand between November and February and is typically between 4pm and 6pm on weekdays.

There must be at least ten days between each Triad, and the actual Triads cannot be known for sure until the end of February. So clients wishing to avoid some/all of these charges will need to exercise judgement about when to reduce their demand.

At amber energy™ we run a FREE Triad Alert service to assist those clients who want to benefit from reducing their electricity usage when Triad risk is high.

Triad charges have risen substantially over recent years, so we'd advise all clients to check the current cost/benefit of avoidance actions.

To find out more and sign up to this free service just email our team on