The gas-turbine engine has relatively poor performance at part-load, and power output deteriorates during the hot season. Therefore the use of water injection in a regenerative cycle, utilising the exhaust waste energy in the recuperator and the water-heater, is expected to recover the de-rated power and improve the fuel economy at lower cost and higher reliability than in the combined cycle. In this research the performance of the evaporative regenerative cycle ERC is analysed parametrically, taking as the main variables the compressor pressure-ratio R(c), turbine inlet temperature T-03, and water:air ratio w. A specially designed computer program was tailored for the analysis, where the main variables are changed over wide ranges. The relative effect of water injection is demonstrated by comparison of ERC with an equivalent regenerative cycle RC. The results show that ERC outperforms RC by about 57% in power and 13% in efficiency, and that water injection would compensate for the power de-rating of engines during the hot season.