Utility giant E.on will be fined £7m by the Gas and Electricity Markets Authority for failing to supply its business customers with smart meters.
The Big Six supplier has agreed to pay the fine to the Carbon Trust for missing an April deadline to ensure 20,000 of its eligible business users had access to the energy-saving devices. It had five years to reach the goal, set out in 2009.
According to the energy watchdog Ofgem, E.on was given the chance to "demonstrate that it had taken all reasonable steps to install advanced meters at all outstanding premises as at 6 April 2014" but was unable to do so.
A spokesman for the company said: "Installing advanced meters to tens of thousands of business customers across the country was always going to be a significant challenge and one that threw up a variety of hurdles for suppliers to overcome. That said, we cannot, and will not, overlook the fact that we did not do enough in time to meet the deadline and in that regard failed to provide the efficient service our business customers demand and deserve."
He added: “In the last 18 months we have made some further progress and we have invested heavily in increasing our capability and we are taking all reasonable steps to get these meters installed."
The fine could double if the energy supplier fails to meet a new interim target, as well as a potential ban on attracting new clients unless it can offer them smart meters upon signing up.
Ofgem is also investigating the rollout performance of E.on rivals British Gas and Npower.
Shares in E.on closed down 2.5 per cent.