The marine energy sector is experiencing a growing interest; large offshore wind farms continue to emerge, particularly in northern Europe. The electrical energy produced by these turbines is intended as clean and renewable. Operations and Maintenance (O&M) of offshore wind farms is however costly and generating environmental impacts. Indeed in view of the circumstances on the high seas the accessibility to Wind Turbine (WT) is greatly complicated causing long periods of unavailability compared to onshore wind farm. To remedy this, operators will mobilize significant and specific resources (Fast Crew Boat, large boat, helicopters). The use of these vehicles and systems of maintenance can improve the availability of WTs but also degrade the environmental performance of offshore wind farm. The optimization of O&M requires rethinking the concept of maintenance of renewable energy systems in mobilizing the concept of Eco-Maintenance. Eco-Maintenance aims to minimize the environmental losses due to maintenance while maximizing the environmental benefits generated assuming the energy recovered due to better maintenance / availability equivalent to an environmental gain corresponding to the environmental impacts of a thermal power plant should have been put into operation to produce this energy. This approach is tested on an offshore wind farm. In this context, modeling the complex system (Offshore Wind Farm + Maintenance Systems) was developed. The various models show that the environmental performance of Systems of Energy Production and System of Maintenance (SM) are interconnected.