Peter Rothstein has a job with a social purpose: expanding the clean energy industry in the northeastern United States as a way to mitigate climate change. Soon, he will be able to support that mission when he saves for retirement .

In November, the Boston-based Northeast Clean Energy Council, where Mr. Rothstein is president, will revise its 401(k) plan investment offerings to include mutual funds promoting those sustainability goals. The revamped plan will include a target date fund series that screens for environmental, social and governance factors — so-called E.S.G. investing. The council, a nonprofit business alliance of 250 companies, will continue to offer traditional choices such as total-market index funds, but the E.S.G. option, Natixis Sustainable Future funds, will be the default investment choice for Mr. Rothstein’s staff of about a dozen employees.

Mr. Rothstein views the shift as a natural evolution. “We have the expertise to understand that these new business models have the potential to be climate solutions and to grow the economy at the same time,” he said. “With that perspective, it makes sense for us to incorporate E.S.G. investing for our retirement plan.”

The idea of investing with a social purpose is gaining ground. The broad category of sustainable and responsible investing grew 38 percent in the United States from 2016 to the start of 2018, to $12 trillion in assets under management, according to the US SIF Foundation. That represented one out of every four dollars of the $46.6 trillion under management, the group noted. A wide range of investments were held, including mutual funds, annuities, E.T.F.s and closed-end funds.