The film (below) follows the group, whose hits include 'All rise' and 'Breathe easy', as they undergo an unconvincing transformation, led by their new manager - band member Anthony's 'uncle'.
The aim is to create the world's first "sustainable energy boyband", the manager says. The campaign includes the chance to see 'Green' perform a one-off gig at Proud Camden this evening (11 December).
To win tickets, fans are being asked to visit npower's Facebook or Twitter page and suggest green-themed names for the band's (fictitious) new album.
Band member Duncan James said: "We are delighted to be making our debut as 'Green' and doing a special gig with npower to support the Go Green tariff. We know our fans will 'all rise' to the challenge and 'breathe easy' this winter knowing their energy needs are taken care of."
Golin, which is facing a review but hopes to retain npower as a client, handled PR for the stunt.