Believe it or not, energy efficiency is big business, and it's only getting bigger. HSBC estimates that the market could grow from $87 billion today to $245 billion per year by 2020. Numbers like that are hard to ignore, especially given that investors are by and large ignoring the energy efficiency opportunity right now.

One thing is for sure, though: Wall Street stalwarts such as Bank of America and Goldman Sachs are not. In this video, Fool.com contributor Aimee Duffy looks at the recent energy investments at these banks, and what investors should take away from their specific initiatives.

Fool contributor Aimee Duffy has no position in any stocks mentioned. The Motley Fool recommends Bank of America and Goldman Sachs and owns shares of Bank of America. Try any of our Foolish newsletter services free for 30 days. We Fools don't all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.