Ambitious targets for reducing carbon dioxide (CO2) emissions are set by Norwegian authorities to address the concerns about global warming. Emission reductions in the offshore heat and power sector can play a role in reaching these targets. Parts of the efforts in industry and academia to reduce offshore emissions are concerned with introducing new design configurations or proposing novel operational strategies for the combined heat and power cycles. Therefore, there is a desire to have a fast and reliable design and assessment tool to be used in the early design stage. Here, a generalized design and performance simulation tool is developed presenting a design point and off-design simulation of the offshore heat and power cycles. It helps the designer provide a fast and accurate thermodynamic assessment of proposed design solutions. The tool has a graphical user interface to facilitate working with the tool with a minimum level of effort and background knowledge from the user. Five part-load control strategies are included in the tool. The tool is verified with available data in the open literature and the results are shown to be in good agreement with the reference data. A combined heat and power cycle is designed and simulated at part-loads as a case study. The cycle includes a gas turbine, a process heat extraction unit, and an organic Rankine bottoming cycle. The simulated performance of the design case in various control strategies is compared showing a 2.5% emission reduction relative to the baseline control strategy.