Century City private equity firm Ares Management announced Friday that one of its subsidiaries will buy Boston’s Energy Investors Funds, an asset manager focusing on energy infrastructure with about $4 billion in assets under management.

The firm invests mostly in electrical utility facilities and companies. One of its portfolio investments is a plant that will generate electricity by burning gas from the Sunshine Canyon landfill in Sylmar.

Energy Investors’ management team will join Ares’ private equity practice. After the transaction is complete, Ares Management will manage more than $7 billion in energy-related investments. Ares has total assets under management of about $80 billion.

“EIF represents exactly what we look for in pursuing accretive, strategically valuable acquisitions,” Ares President Michael Arougheti said in a press release.

Ares stock lost 2 percent Friday to close at $15.84.