According to the UK gas and electricity market regulator Ofgem (Office of Gas and Electricity Markets), the six largest power and gas suppliers of the United Kingdom (collectively referred to as the "Big Six") saw their profits dive by 10% in 2017, from £1bn (€1.14bn) to £900m (€1.03bn) and their market shares erode by a combined 5 percentage point, due to a fiercer market competition.
73 energy suppliers are now competing on the market. Between June 2017 and June 2018, smaller suppliers gained 1.4 million customers, who were previously supplied by the Big Six, as switching rates reached a record high. 25% of UK's gas customers and 24% of power customers are now supplied by small and medium-sized suppliers.
The Big Six refer to British Gas (Centrica), Scottish and Southern Energy (SSE), Npower (whose merger with SSE was approved earlier in October 2018), ScottishPower (Iberdrola), Uniper (ex E.ON) and EDF Energy. British Gas maintained an 8% margin, while SSE, Uniper and ScottishPower made margins of 7%, 5% and 0.5%, respectively.