Drax said the coronavirus-related loss came mainly from its customer business, which sells power, gas and energy services to small to medium-sized (SME) companies.
The company, which has the capacity to provide electricity to around 13 million homes, saw stronger generation from its biomass plants, up 16% compared with the first half of 2019 to 7.4 terawatt hours.
Drax has converted four of its six former coal-fired units in the past decade to use biomass wood pellets.
The remaining coal plants are set to close by the end of March 2021, ahead of a government deadline of 2024, but will remain able to fire up to provide back-up power, until September 2022, the company has said.
The closures are expected to lead to a 25-35 million exceptional item in the second half of the year, Drax said.
First half adjusted EBITDA rose 30% to 179 million pounds, helped by higher power generation and a reduction in costs for its biomass supply.
The company said it would pay an interim dividend of 6.8 pence per share and expects a full year dividend of 17.1 pence, up 7.5% compared with 2019.
"We have increased our dividend while also helping to keep the lights on," Drax Group CEO Will Gardiner said in a call with journalists.
(Reporting by Susanna Twidale; Editing by Gareth Jones)