The company has called in Grayling to help it square up to giants such as Npower, which PRWeek revealed last week was overhauling its comms.
The appointment to the national PR brief, on which Cuban Eight was the incumbent, follows a pitch process.
Grayling will look to raise awareness of First Utility as a provider of competitive energy tariffs, and promote its range of online services, while positioning the company as one that helps the public lower its energy bills.
Work will also focus on raising awareness of 'behavioural insight tools', such as My Energy, which encourages customers to manage their energy consumption.
Grayling CEO Alison Clarke will lead the work alongside the agency's consumer head Tristan Pineiro.
First Utility chief marketing officer Ed Kamm said that the focus would be on positioning the company as 'a compelling energy supply alternative'.