The pitch was also contested by agencies including Craik Jones Watson Mitchell Voelkel, Geronimo and Entire.
Npower has tasked the agency with creating a programme of direct marketing activity both in print and online to help acquire high value customers.
The value of the account has not been disclosed and is dependent on the range and scope of the projects undertaken.
Neil Hodgetts, channel marketing manager at npower, said: "We look forward to working closely with EHS Brann to provide us with an end to end approach to our DM and help improve both our sales and customer engagement going forward."