This paper presents the thermos-economic evaluation of a simple gas turbine (SGT) within the Niger Delta, Nigeria. Steady-state monitoring and direct collection of data from the 25 MW plant were performed including logged data for a 12 months period. MATLAB software was used to model the various thermodynamic performance equations of the plants while net present value (NPV), internal rate of return (IRR), and Payback period (PBP) were used to model the economic concept of the plant performance. The thermodynamic analysis shows that for every 1℃ rise in the ambient temperature, the percentage power drop increases by 2.07%, thermal efficiency drops by 0.66%, and the specific fuel consumption increases by 0.93%. For every 1% drop in the power output, the percentage thermal efficiency drops by 0.79% for the given consideration. The economic analysis based on the performance reveals that the power shortages represent about 47.9% of the net power generated and the revenue worth of $4198741.60 is lost due to the inability of the plant to perform at its design point. The NPV value of $6434899.97 shows that the plant investment is viable for the period of twenty years of operation and the IRR on investment is determined to be 12.40% by a numerical approximation for the period, with a PBP of 8.5 years. This provides technical and economic details to plant operators and energy systems investors for decision making.