"The path toward sustainable energy sources will be long and sometimes difficult. But America cannot resist this transition. We must lead it. We cannot cede to other nations the technology that will power new jobs and new industries." -- President Barack Obama 

A fair wind blows for renewables of late, and it may hearken a new era of growth for wind and solar. In Monday's inaugural address, President Obama made specific mention of his aim to promote sustainable energy, and utilities have been building up their renewable portfolios. Warren Buffett just added the largest solar project in the world to his steadily growing renewable energy portfolio . Meanwhile, new models have arisen to make solar energy more accessible to retail customers. Despite some notable challenges, it all bodes well for what some are predicting will be the U.S.' energy renaissance.

The stage, the players
According to the U.S. Energy Information Agency (EIA), renewable energy and natural gas compose the majority of generating capacity that has been bought and sold since 2005. The U.S. electric power market in 2012 featured the purchase and sale of 107 gigawatts of operating capacity, the majority of which came from three mergers or acquisitions. Duke Energy (NYSE:DUK) merged with Progress Energy in July 2012; Exelon (NASDAQ:EXC) merged with Constellation Energy in March 2012; and NRG Energy (NYSE:NRG) acquired GenOn Energy in December 2012. Since then, all have been busy in the renewables space.

In December, Duke received two loans, each worth $110 million, to build two Texas wind farms. The projects -- Los Vientos I and Los Vientos II -- will generate a combined 402 megawatts (MW). Duke recently finished its 12.5 MW solar farm in eastern North Carolina, which has enough capacity to power around 3,000 homes. The company also has a 15-year agreement with North Carolina Eastern Municipal Power Agency to supply electricity from its recently completed Washington White Post plant in Beaufort, N.C. This is the largest solar facility Duke operates in the eastern U.S. Altogether, Duke nearly doubled its renewable operating capacity last year. 

In December, Exelon brought its 40 MW High Mesa Wind in Idaho online. The company sells the electricity generated from High Mesa to Idaho Power under a long-term contract. This is part of Exelon's stated strategy to increase its renewable and clean energy generation capacity while retiring its dirtiest coal-fired plants. The company is also building its Antelope Valley Solar Ranch One in California. When it enters full commercial operation in late 2013, AV Ranch One will be one of the largest solar photovoltaic projects in the world.

NRG is the U.S.' largest solar power developer. In December, the company's solar business arm, NRG Solar, announced that its Avra Valley Generating Station in Arizona had come online. Under a 20-year power purchase agreement, NRG will supply the power it generates to Tucson Electric Power. NRG is expanding its portfolio of renewable energy assets, including wind and solar. CEO David Crane is widely recognized as an industry leader in green energy.

Renewable energy veterans continue their progress as well. General Electric (NYSE:GE) is the U.S. largest wind turbine manufacturer. In the last month, GE bought a 40% stake in a European renewable energy business, and has an aggressive strategy to challenge rival Siemens' dominance in the German onshore wind- turbine market. Closer to home, GE's 235 MW Chisholm View Wind in Oklahoma came online this December.

The Buffett Effect
Warren Buffett himself is betting on renewables. Just this month, the electric utility MidAmerican Energy Holdings -- which Buffett's Berkshire Hathaway owns -- acquired two co-located Southern California solar power projects, creating the largest solar power project in the world. The 579-MW Antelope Valley Solar Projects are the most recent addition to Buffett's expanding renewable energy portfolio.

Potential pitfalls
While I believe 2013 is going to be a banner year for renewables, investors should watch out for a legislative hotspot. Wind and solar remain somewhat dependent on tax breaks and subsidies for viability in competition with other energy sources. In the fiscal cliff wrangling, these supports are far from assured. While they received a temporary reprieve, the long-term risk remains.

The Production Tax Credit (PTC) is of particular importance to wind developers. Many say that their businesses will fail without it, and the American Wind Energy Association (AWEA) defends that position aggressively. Interestingly, though, Exelon is lobbying heavily against the PTC, saying that it does nothing to benefit consumers and constrains market innovation. Xcel Energy (NASDAQ:XEL) shares Exelon's position, even though Xcel had the largest wind capacity of any utility in 2011. The company is reviewing its membership in the AWEA because of this difference in opinion, and has gone so far as to say that it may not buy more wind because of its opposition to the PTC. My bet is that Exelon and Xcel are positioned for resilience no matter which way the regulation goes.

On the solar side, energy analysts from UBS issued a ground-breaking report entitled "The Unsubsidised Solar Revolution." According to the report, "Solar has turned from a heavily subsidised marginal technology into a mainstream source of power generation. Thanks to significant cost reductions and rising retail tariffs, households and commercial users are set to install solar systems to reduce electricity bills -- without any subsidies." If the same happens in the U.S. -- and I think it's just a matter of time -- then solar will stand just fine on its own two feet.

Renewable energy is coming. Obama said it, Buffett clearly believes it, and scientists are begging for it. Signs are pointing to 2013 as a great year for clean investment.