The U.S. Senate Energy and Natural Resources Committee heard the testimony of five witnesses in its review of a draft federal renewable electricity standard that could require that 20% of the nation's power be produced by renewable energy sources by 2021. Legislation to implement a federal renewable electricity standard is one of President Obama's highest priorities, said Committee Chair Sen. Jeff Bingaman in his opening remarks. Ranking member Sen. Lisa Murkowski noted that 28 U.S. states and the District of Columbia had so far implemented renewable portfolio standards (RPSs), but she stressed it was imperative to address how a “one-size-fits-all” standard would fit regional energy-supply disparities.

In the previous Congress, the House passed a federal standard that would have set a target of 15% by 2020 and would have allowed up to 4 percentage points of that requirement to be met with energy-efficiency measures. The RPS provision in that bill stalled negotiations between the parties, however. The Bush administration had also threatened to veto it.

But a similar bill has a better chance of passing now, analysts say, owing to a Democratic majority in Congress and President Obama's pledge to push for a 25% mandate, with a 10% standard achieved early in the next decade. Attempts to push the standard are already under way, including the American Renewable Energy Act, which, if passed, would require the nation to produce 25% of its electricity from clean sources by 2025 and would take effect in 2012.

The Democratic staff draft for Sen. Bingaman's proposed renewable electricity standard requires utilities to ensure that a certain percentage of electricity sold was derived from renewable sources. Per the draft, that minimum would be 4% between 2011 through 2012, and 8% through 2015.

Lester Lave, a professor of economics at Carnegie Mellon University, was one of the witnesses at the Senate's committee hearing. Prof. Lave urged the committee to focus on reducing CO₂ emissions with a carbon portfolio standard rather than “singling out renewables as the answer.” He said there are “significant savings from letting all technologies compete in satisfying the goals of lowering greenhouse gas emissions, increasing environmental quality more generally, increasing energy security and improving sustainability.”

Lave also pointed to technical difficulties of connecting large amounts of wind and solar energy into the national grid. “In general, wind and solar power are not available when demand is highest. Wind tends to be strongest at night and lowest in the summer. Solar power is best in the summer, but the Arizona data show that the arrays have all but stopped producing electricity by 5 p.m. in the summer, just as demand is hitting its peak,” he said.

One solution to the problems of relying on renewables was to increase research into energy storage. “Pumped hydro storage is the best way to store electricity but few new sites are available. Compressed air storage looks promising, but is expensive and less efficient than pumped hydro,” he said.