The company sends its magazine, called Gridline, to all members of the public who have National Grid equipment on their land. Summersault produced the first edition under its tenure at the end of last year.
Gridline is designed, written, edited and printed by Summersault, and has an estimated readership of 32,500.
The magazine contains updates on National Grid projects, plus information about grantors - people or organisations who have electricity pylons or gas pipes on their land - such as city councils.
Clare White, National Grid's land and development policy manager, said the company needed a publication that "was going to grab people's attention and be used as a reference tool throughout the year".
Summersault Communications' other clients include Camelot, Danone, McDonald's and Siemens UK.