Lennard, who has handled Ovo as a client while leading Edelman’s public affairs energy practice, is to join in July as head of corporate affairs.
She told PRWeek that the new role comes as Ovo aims to develop from being a "figurehead challenger brand" to "leading the change" in an industry seeking to rebuild public trust amid ongoing scrutiny.
Lennard advised Ovo’s CEO Stephen Fitzpatrick on a high-profile select committee appearance last year after criticism of energy suppliers was ratcheted up following Labour leader Ed Miliband’s pledge to freeze energy prices.
"Ovo has had a fantastic year, but things will only get hotter from here," she said.
"We are a small company growing quickly within a hugely controversial industry in the eye of a political storm, and as a challenger brand Stephen has done a great deal to help give the company a platform, but now it’s about looking at how we use that platform and where the company goes with it."
Lennard was hired by Edelman three years ago to launch an energy specialism within its public affairs practice, having done the same at Hanover Communications.
Before this, she was a member of the Tories’ energy team in opposition and went on to act as campaigns manager at CCHQ ahead of the 2010 General Election.
Ovo has hired her as part of wider efforts to build up its comms, which is currently handled by one comms specialist as well as by the marketing department and the company more broadly.
Though declining to go into specifics, Lennard said she expected more arrivals on the team shortly, adding: "Customers are dissatisfied with the Big Six [the biggest energy providers in the UK market] and Ovo does not want to create the Big Seven. We want people to understand that this growth will not compromise our belief in simpler, fairer and cheaper energy."
Her departure from Edelman comes as the agency narrows down its search to replace public affairs head Stephen Lotinga, who left to become Deputy Prime Minister Nick Clegg's director of communications earlier this year just weeks after being appointed to replace Chris Rumfitt.