Quite a few computer programs have been developed to model power plant performance. These software codes are geared toward modeling steady-state operations, which are usually sufficient for conventional power plants. Solar thermal power plants undergo prolonged transient start-up and shut-down operations due to the periodic nature of solar radiation. Moreover, the large size of the solar field brings about large residence time that must be considered to accurately lag power generation. A novel scheme has been developed to fine-tune steady-state solar power generation models to accurately take account of the impact of those transient operations. The suggested new scheme is implemented by adjusting solar radiation data input to the model and has been shown to clearly improve modeling accuracy by moving modeled results closer to matching real operating data.