The dynamical energy efficiencies of electrical power systems in Macau Coloane power plant had been investigated. Thermodynamic models for the efficiency of a simple cycle water injection gas turbine with rotor air cooling application and multi-shaft combined cycle power plant (CCPP) were developed and validated by comparing to the real data from the power plant in Macau, which is composed by two water injection gas turbines (WIGT) fueled by natural gas, two heat recovery boilers and one steam turbine. The result obtained from the present model has higher accuracy compared to previous models due to the application of dynamic values of the parameters such as injected water ratio. The optimal value for the ratio of injected water is obtained based on the present thermodynamic model and validated by the measured electrical efficiency. The present model is helpful in the operation of the water injection gas turbine power plant and the CCPP system. Besides, the present study also developed a new real time prediction models for output power and energy efficiency of solar photovoltaic (PV) systems. These models were validated using measured data of a grid-connected solar PV system in Macau. Both time frames based on yearly average and monthly averages are considered. It is shown that the prediction model for the yearly/monthly average of the minutely output power fits the measured data very well with high value of R2 . The online prediction model for system efficiency is based on the ratio of the predicted output power to the predicted solar irradiance. This ratio model is shown to be able to fit the intermediate phase (9am to 4pm) very well but not accurate for the growth and decay phases where the system efficiencies are near zero. It is shown that the maximum monthly average minutely efficiencies vary over a small range of 10.81% to 12.63% in different months with slightly higher efficiency in winter months.