Power to businesses, streetlamps and traffic lights was lost in Hemel Hempstead town centre yesterday evening.
Engineers from UK Power Networks had isolated supplies to 67 properties in Waterhouse Street and Marlowes at around 6.15pm due to a fault.
Power was restored an hour later once repairs had been carried out – but the problem also affected street lights in the town centre and alongside the Water Gardens, as well as the traffic lights at Bank Court.
While most Marlowes businesses had closed for the day before the cut struck, town centre fitness centre Fit4Less lost power and was forced to cancel classes and turn away gym-goers.
Greenford Contractors, who are carrying out improvements to the Marlowes area including planting new trees, confirmed the problem was not caused as a result of its works, and all its engineers had left the site by 4.30pm.
Similarly, highways contractor Ringway – which is carrying out roadworks to the footpath on Waterhouse Street – also said their scheme of work was not to blame.
A spokesman for energy firm UK Power Networks said: “We apologise to customers in Hemel Hempstead as we had to interrupt power supplies yesterday evening to carry out an emergency repair to some electrical equipment.
“We appreciate how difficult it can be to lose power and apologise for the inconvenience caused.”