Solar, biomass and wind could be considered the big three in clean energy, but there are several interesting niches emerging, especially for those scouting for more immediate M&A opportunities. Companies that add intelligence to the electric grid might not generate headlines — or electricity, for that matter — but some of these small companies are already showing a return on investment to the utilities they market to. At the Clean Energy Venture Summit in Austin, Texas, four startups pushing their version of smart grid technology pitched their wares. All believe that using Internet protocol to connect aspects of the electric grid and devices using electricity will result in more energy efficiency, but each varies in how they plan to achieve this.

Silver Spring Networks already has raised a Series C round and views itself as an aggregator of smart grid technology that boosts efficiency at utilities. PCN Technology Inc. is close to closing on its Series A and plans to use existing wires for transmitting and networking small amounts of data. NovusEdge Inc. has raised $30 million and makes software that helps control heating, lighting and access in commercial buildings. The youngest company is GridAgents, which is seeking $3 million to $5 million in Series A and offers software that monitors and processes streaming data in real time. Interestingly, GridAgents was one of the first of several companies presenting at the conference that freely acknowledged it was targeting an exit via an acquisition rather than an initial public offering. Clean energy may be a growing bubble, but it's a bubble that isn't demanding sky high stock valuations, at least not yet. Will investors reward such pragmatism?—Stacey Higginbotham