Offshore wind is a growing source of energy globally. Like any energy technology, it has impacts on the environment. In the case of renewable energy, we need a way to consider the environmental benefits as well as the environmental costs. This dissertation develops a set of models to examine the economic and environmental costs and benefits and the trade-offs between them. We ask how much offshore wind energy should be sited, and where should that offshore wind energy be located? The first model estimates the economic impact of wake interactions between wind farms. Wind farm sites are chosen through a portfolio model with an underlying network model to track the wake effects. The second model estimates the local costs of offshore wind in terms of avian fatality impacts of potential offshore wind projects and the trade-offs with project size and cost. A Markov model estimates potential fatalities and can be used to negotiate between conservation and renewable energy goals. The third model examines the global value of offshore wind energy in terms of mitigating carbon emissions and climate change. We use an integrated assessment model to examine how offshore wind energy competes with other energy technologies and reduces emissions under different policies and scenarios. These models all fit into a framework for estimating the trade-offs between the local and global, economic and environmental performance of offshore wind energy.