The UK’s electricity transmission system has two main components.
National Grid, Scottish Power and SSE manage the high voltage “grid” that carries electricity over the long distances from power plants to the regions where it is needed. Eight regional distribution companies then take that power from the grid and deliver it to homes and businesses across Britain.
SSE runs two of these, Scottish Power runs two more and National Grid runs a fifth. The North East is covered by Northern Powergrid and the North West by Electricity North West.
The largest by customers is UK Power Networks, serving 8.3m homes and businesses across London, the South East and East of England. It is owned by CK Infrastructure, a Chinese company.
A spokesman for the Energy Networks Association, which represents the industry, disputed the use of company operating profits as a way of assessing their performance.
He argued that because the industry was highly capital-intensive, a better measure would be return on capital – which averaged around 5pc.
The spokesman said: “Network companies aren’t making excessive profits. Their returns are regulated by Ofgem and average around 5pc. Running, maintaining, and upgrading the electricity network costs about 48p per day on your energy bill.
“This supports 26,000 jobs, 1,500 apprenticeships – with 700 more being recruited this year, and maintains over 500,000 miles of wires and cables.
“Additionally, network operators are investing more than £30bn in the coming years to ensure a reliable energy grid.”
A Department for Energy Security and Net Zero spokesman said the profits of energy suppliers and distributors were regulated by Ofgem – which is carrying out a review of the standing charges.
Ofgem did not comment directly on Mr Vince’s demands but pointed to a previous statement, which said: “Network companies, including distribution network operators, are funded through the network price controls which Ofgem allocates.
“Funding includes allowances for replacement, repair and refurbishment to network infrastructure.
“Funding, which is recouped via energy bills, is regularly reviewed to ensure levels are appropriate for the work required to ensure the maintenance and development of safe and reliable energy networks.”