June 21 (Reuters) - Octopus Energy is set to hand the next UK government an early 3-billion-pound ($3.80 billion) windfall as it pledged to repay all the state support it received to take over collapsed energy supplier Bulb, the Financial Times reported on Friday.

Octopus would reimburse the Treasury by September, meaning that the government will recover almost all the cost of temporarily nationalizing Bulb in 2021, the report said.

"We have already started to repay the government and it should all be complete by September," FT quoted the company as saying. ($1 = 0.7900 pounds) (Reporting by Jahnavi Nidumolu in Bengaluru; Editing by Savio D'Souza)