Society must develop a large new source of electric power to adequately meet human needs in the 21st Century. The Lunar Solar Power system (LSP) is a new option that is independent of the biosphere. LSP captures sunlight on the moon, converts the solar power to microwaves, and beams the power to receivers on Earth that output electricity. The collimated microwave beams are low in intensity (< 20% of sunlight), safe, and environmentally benign. Data Envelopment Analysis (DEA) enables the detailed quantitative comparison of alternative economic systems. We use DEA methodology to compare the technical efficiency of the large-scale power systems needed to meet the growing energy needs of terrestrial society. This comparison suggests the efficiencies to be gained from LSP are large indeed. Such gains remain even if the resources needed for LSP are 10-fold greater than estimated from United States government studies. In terms of benefits versus costs, normalized to the range of 0-1, DEA reveals that LSP is much more efficient than conventional terrestrial solar-thermal and photovoltaic, fossil and nuclear systems. LSP is also environmentally benign compared to the conventional systems.