A breakthrough in solar cell technology promises to make solar power a cost-competitive energy option and to reduce U.S. dependence on oil.

With funding from the Department of Energy, Boeing-Spectrolab has managed to create a solar cell with 40.7% sunlight-to-energy conversion efficiency, said DoE assistant secretary for energy efficiency and renewable energy Alexander Karsner on Tuesday.

The solar cell represents "the highest efficiency level any photovoltaic device has ever achieved," according to David Lillington, president of Spectrolab. That claim has been verified by the DOE's National Renewable Energy Laboratory in Golden, Colo.

Most of today's solar cells are between 12% and 18% efficient. Some of the ones used to power satellites are around 28% efficient. In 1954, 4% efficiency was state of the art.

High energy prices and environmental concerns are prompting businesses to consider solar power. In October, Google said it planned to install 9,200 solar photovoltaic panels at its Mountain View headquarters in 2007. Google's solar panels, made by Sharp, are 12.8% efficient. It expects to generate 30% of its peak energy usage during the summer from solar power.