This paper describes gas turbine/solar trough hybrid designs that achieve a solar contribution greater than 50% and increase the solar-to-electric efficiency while reducing gas heat rate. Two conceptual designs are explored: (1) integrating gas turbines with conventional oil heat-transfer-fluid (HTF) troughs running at 390 degrees C, and (2) integrating gas turbines with salt-HTF troughs running at 450 degrees C and including thermal energy storage (TES). The latter system is also representative of molten-salt power towers, although the power towers run at temperatures near 565 degrees C and would require selection of an appropriate gas turbine to provide waste heat at those temperatures. Using gas turbine waste heat to supplement the TES system provides operating flexibility while enhancing the efficiency of gas utilization. The analysis indicates that the hybrid plant designs produce solar-derived electricity and gas-derived electricity at lower costs than either system operating alone. (C) 2013 Published by Elsevier Ltd.