The cogeneration system and the CO2 compression power plant of an offshore platform on the Brazilian coast are assessed under off-design conditions along the expected lifetime of an oil well. These power plants are projected to supply thermal and electrical requirements of the Floating, Production, Storage, and Offloading (FPSO) unit and operate predominantly under off-design conditions either under atmospheric conditions, partial load, or even at a pressure drop due to up- and downstream equipment. A thermodynamic analysis was carried out from the air humidity and the temperature profile, as well as the correction factors for performance parameters at partial load. Besides, a comparative analysis for an alternative configuration with inlet air cooling technology aiming at mitigating CO2 emissions was also performed. The results present an increase of 7%, on average, in exergetic efficiency; besides, 6% of mitigated CO2 emissions was achieved. Additionally, the occupied area would be just slightly impacted. Otherwise, the power plant weight is expected to increase by 2.87 and 6.6%.