Nothing near that amount will actually be accomplished by the mandate — or even required — because of compromises made to exempt some utilities and permit others to substitute efficiency improvements for a large portion of the renewable energy need.

By contrast, Obama – both in the presidential campaign and from time of occupying the White House – has given a call for a much more aggressive move to renewable energy. He set an aim of 10 percent renewable energy use by power producers by 2012 and 25 percent by 2025.

The bills before Congress would need a modest three to six percent renewable energy use by most utilities over the coming three years. Presently, total U.S. renewable energy use for power generation is near three percent, not counting hydroelectric power.

Sponsors of the Senate and House renewable energy bills had wanted a more aggressive approach, but have had to accommodate a chain of compromises to harness the needed support for passing any kind of national mandate.

In what is viewed by renewable energy advocates as a major weakening of the mandates, the House bill permits utilities to meet 40 percent of the need by adopting energy efficiency programs. The Senate proposal would allow 25 percent of its target to be met by efficiency improvement.

But the measures have been diluted even more by other provisions.

Both bills, for example, would exempt most publicly owned utilities that account for nearly 10 percent of the nation’s electricity.

The measures also would scale back the mandate if a utility builds a coal plant that can capture carbon dioxide, builds a new nuclear power plant, or increases power generation from an existing reactor.

Since the full impact of the requirement won’t be felt for a dozen years, there’s a good likelihood such plants will be built.