Westminster Strategy has handled the brief for the past three years but its contract expires at the end of next month.
TXU head of UK government affairs Jennifer Hands insisted she did not know whether she wanted further agency assistance, but a pitch could be held as early as the autumn, she confirmed.
TXU - the Texas-headquartered firm that entered the UK market four years ago when it bought the then Eastern Electricity - is now the third-largest energy supplier in the UK, behind Centrica and Innogy's npower.
It handles most of its PA for continental Europe in-house but appointed Edelman PR Worldwide on a PA remit in Brussels in April.
Hands said Westminster Strategy has handled UK profile-raising and political monitoring work, in addition to providing strategic advice on the Government's ongoing Energy Policy Review.
Meanwhile, Ely-based Myriad PR has scooped a media relations brief for TXU's corporate social responsibility programme.
The account, won after a competitive pitch, sees Myriad tasked with boosting TXU's profile in the local, regional and trade press.
TXU has around 2,000 UK employees, most of whom work at its HQ in Ipswich. Its retail business - TXU Energi - also has staff in London, Lancashire and Essex.
The company owns three power stations in the Midlands, various wind farms and hopes to start construction of a wind farm in the Solway Firth next year.
Community relations manager Paul Henry said that by the end of this year, he wants to have doubled the number of employees taking part in volunteering projects and taking advantage of a scheme by which TXU matches pound-for-pound cash employees raise for charity. Last year five per cent of employees volunteered and three per cent raised money for charity.
TXU retains Manning Selvage & Lee for PR on its TXU Energi brand.