Solar aided power generation (SAPG) is an efficient way to make use of low or medium temperature solar heat for power generation purposes. The so-called SAPG is actually 'piggy back' solar energy on the conventional fuel fired power plant. Therefore, its solar-to-electricity efficiency depends on the power plant it is associated with. In the paper, the developed SAPG model has been used to study the energy and economic benefits of the SAPG with 200 and 300 MW typical, 600 MW subcritical, 600 MW supercritical, and 600 and 1000 MW ultra-supercritical fuel power units separately. The solar heat in the temperature range from 260 to 90 degrees C is integrated with above-mentioned power units to replace the extraction steam (to preheat the feedwater) in power boosting and fuel-saving operating modes. The results indicate that the benefits of SAPG are different for different steam extracted positions and different power plants. Generally, the larger the power plant, the higher the solar benefit if the same level solar is integrated. Copyright (C) 2010 John Wiley & Sons, Ltd.