The government has ordered sweeping measures to fight coronavirus, shutting down much of the economy and asking people to stay inside and avoid non-essential travel.
"To provide those affected with certainty over the coming months, and following discussion and agreement with relevant Unions, 3,400 staff across OVO and SSE Energy Services will be placed on furlough leave," OVO Energy said in a statement.
OVO earlier this year completed a deal to buy SSE's retail arm, SSE Energy Services, making OVO the country's second largest energy supplier by customer numbers.
OVO said staff affected will receive 80% of their salary under a government-backed scheme and it would top up payments to ensure everybody received 80% of their total salary, regardless of the government?s cap of 2,500 pounds a month.
"Members of the executive team and senior directors have also volunteered to take a 20% pay cut over the next 3 months," the statement said.
Britain's energy trade association, Energy UK, earlier this week called on the government to offer financial support to energy suppliers to help them offer payment breaks to customers struggling with bills.
A spokeswoman for OVO said suppliers were working together to ensure customers remain supplied with energy.
Britain's largest supplier, Centrica, on Thursday cancelled its 2019 dividend and cut costs in anticipation of an increase in non payments by customers, sending its shares to record lows.
By Susanna Twidale