Almost 100,000 customers left ScottishPower during the third quarter as the energy company prepares to make the switch to fully renewable power.
The total number of UK consumers across electricity and gas fell from 4.87 million at the end of June to 4.78 million.
Earnings rose 410% in its home supply business to £170 million in the nine months to the end of September, however, continuing the division’s recovery from a “very poor” performance in 2017.
The figures come after the Big Six energy company announced last week it would sell the last of its remaining gas plants to Drax Group.
Following completion of the deal, which is expected to finalise at the end of the year, Scottish Power will generate 100% of electricity with wind power.
Chief executive Keith Anderson said: “Over the rest of this year and into 2019 we will be focused on delivering greener electricity for our customers, from offshore and onshore wind as well as new solar developments.”
Earnings in the renewables business were up 19% in the period to £266.7 million, following the completion of a £650 million investment in onshore windfarms in Scotland.
Another project in East Anglia is due to produce its first power in 2019, with full operation during 2020.
ScottishPower’s Spanish parent company Iberdrola reported a 13.5% dip in net profit to 2.09 billion euros (£1.85 billion) for the period, due to lower extraordinary income and the worsening performance of the generation business in Spain.
The group’s core earnings jumped 22.5%, however, supported by double-digit growth in all businesses.