The main criteria to assess a new solar thermal power plant are its performance and cost. Therefore, there is a need to present to the open literature a detailed modeling procedure and cost analyses to help researchers, engineers, and decision makers. The main objectives of this work are to develop a code and to evaluate the optical and thermal efficiencies of parabolic trough collectors (PTCs) solar field considering average hourly, daily, monthly, or annually averaged weather data; in addition to detailed cost analysis of the solar field. In this regard, a computer simulation code was developed using Engineering Equations Solver (EES). This simulation code was validated against Thermoflex code and data previously published in the public literature, and excellent agreements ware observed. The types of the PTC considered in the simulation are EuroTrough solar collector (ET-100) and for LUZ solar collector LS-3. The present study revealed that the maximum optical efficiency that can be reached in Dhahran is 73.5%, whereas the minimum optical efficiency is 61%. This study showed also that the specific cost for a PTC field per unit aperture area and the specific cost of different mechanical works can be cut by about 46% and 48% at 10 hectare and by about 72% and 75% at 160 hectare, respectively, compared to that at 2.8 hectare. On the other hand, the specific civil costs remain constant independent of the plant size. It was found that the ratio of the cost of the PTC to the solar field area decreases significantly as the solar field size increases. This decrement is very significant until the solar field size reaches 60 hectare and then the slope of the decrement is becoming insignificant. Therefore, it is recommended to have a solar field size of 60 hectare or larger.