Nov 20 (Reuters) - Utility firm NRG Energy said on Monday that CEO Mauricio Gutierrez has left the company months after activist investor Elliott Investment pushed for a boardroom overhaul.

NRG Energy named Lawrence Coben, chair of the company's board, as interim CEO and said it has started a search for a permanent chief executive.

The company also named four new independent directors to its board.

Elliott disclosed a more than 13% economic interest in NRG in May and called for strategic changes at the company including a boardroom overhaul.

It was also critical of NRG's $2.8 billion acquisition of Vivint Smart Home, which it termed as "the single worst deal in the power and utilities sector in the past decade".

NRG added on Monday it would conduct a comprehensive review of its operations and cost structure. (Reporting by Arunima Kumar in Bengaluru; Editing by Shounak Dasgupta)