Business Energy specialist, PCMG has seen UK companies spending up to seven-figure sums on TNUoS charges, which have gone up by around 160% since 2010.

Transmission Network Use of System charges cover the cost of transporting electricity long distances from power stations to regional networks. They make up approximately 6% of the total energy bill for big businesses and much more in some cases.

Will Stephens, Senior Energy Analyst at PCMG, said: “TNUoS charges have increased astronomically in the last 15 years. For high energy users, from manufacturing firms to cold storage companies, or just those with multiple sites, it can be a huge cost, representing a big chunk of the energy bill.”

The cost is worked out by looking at energy usage when demand across the system is at its highest between November and the end of February.

“TNUoS charges are based on looking at the three peak half hour periods, known as Triads, of energy use from November to the end of February and then the charge for each business is based on those periods. Typically Triad periods occur most often in December and January, between 17:00 and 18:30 when the tea time rush combines with the commercial demand. The measures have to be 10 days apart and often weather and temperature can play a part.”

According to PCMG, businesses can reduce TNUoS costs by reviewing when energy is used.