The German utility company, which owns Thames Water and npower, is talking to a number of roster and non-roster agencies.
Vizeum handles the bulk of npower's media, while Media. Com handles the digital media account. Thames Water is handled by ZenithOptimedia. The winning agency will handle media planning and buying across both brands.
The review comes as Thames Water looks to increase its adspend to tackle issues surrounding the ongoing water shortage in the UK and promote its involvement in the 2012 Olympics.
The company has been reprimanded by the water regulator, Ofwat, for failing to cut leaks, with nearly a third of water leaking out of its pipes before it reaches customers.
Thames Water is also involved in the development of the infrastructure for the London Olympic Games.
The last ad agency Thames Water appointed was M&C Saatchi in 2004. However, the agency is not working on anything for the brand at present.
Isobel handles advertising for npower, which spends £6 million a year, according to Nielsen Media Research.
The review is being handled by RWE's procurement department, which is drawing up a shortlist.
A decision is expected by the end of the month.
- Things We Like, p14.