How to Balance the Solar Efficiency Equation

The National Renewable Energy Laboratory’s solar cell efficiencies chart depicts confirmed conversion efficiencies for research cells from 1976 to date, for several PV technologies. But as conventional crystalline silicon (c-Si) PV modules approach peak efficiency, with the leap from lab to life—or from demonstration to mass production—occasionally taking over 30 years, the final question is: what is the additional watt class worth?