Earnings (EBITDA) for the six months to June 30 came to £10mln, down from £121mln the same period a year ago.
The power producer said a rail loading outage curbed deliveries of pellets at the start of the year. This led to lower power generation at two of the company’s biomass units.
Drax was affected by another outage at one of its biomass units in February.
The group has converted three of its coal-fired units to burning biomass wood pellets and plans to covert a fourth unit by the end of the year.
Interim dividend lifted as full year guidance maintained
Drax, which generates about 6% of Britain’s electricity, said its full-year EBITDA expectations were unchanged. It raised its interim dividend to £22.4mln, or 5.6p per share, from 4.9p last year.
"We remain focused on safe and efficient operations and returns to shareholders and expect to declare a full year dividend of £56mln for 2018," said chief executive Willi Gardiner.
The higher dividend payment follows a £50mln share buyback programme announced in the 2017 results in February.
Shares fell 4.6% to 335p in morning trading.
Have investors had enough?
"With yet another disappointing earnings report today, have the investors finally had enough?," said Artjom Hatsaturjants, research analyst at Accendo Markets.
"A combination of poor results and new capital allocation plans seem to go hand in hand for Drax Group lately.
"And while utility companies typically boast healthy dividend yields (Centrica 8.74%, United Utilities 5.55%, Severn Trent 4.69%), is Drax Group (4.55% dividend yield) perhaps struggling to keep up with larger industry peers in maintaining superior return on shareholder equity?"