Britton joins the energy company on 1 February from her role as strategic marketing director at insurer Axa UK, having previously held the position of head of marketing at Norwich and Peterborough Building Society.
She replaces Kevin Peake, who left Npower in August following 11 years with the brand, before subsequently joining Aviva as interim brand, sponsorship and corporate responsibility director.
Giuseppe Di Vita, managing director, customer markets at Npower, said: "Debbie joins the industry at a time when it faces many challenges on many different fronts.
"Perhaps our most important challenge is to re-engage with consumers to rebuild levels of trust. I have no doubt we have the team in place at Npower to begin that journey."
Last year, Npower rolled out a loyalty programme offering to reward consumers with exclusive deals from brands to which it provides energy services. The 'In Good Company' scheme provided deals from Caffe Nero, the Football League and the National Trust.