Solar energy development is an increasingly cost-effective way for communities to diversify their energy portfolios, promote local economic growth, and help to protect the nation's natural resources. Recognizing the potential benefits of solar power, state and local governments across the United States have introduced tax credits, subsidies, rebates, and other policies in recent years to promote solar energy within their boundaries. Most of these policies seek to encourage solar energy development by offsetting the real cost to landowners of installing solar energy systems on their properties. Although these valuable programs clearly increase voluntarily solar energy installations within a jurisdiction, many of them can also require substantial government funding. Because of widespread state and municipal budget pressures, such policies are increasingly difficult to enact and maintain at the local level. Fortunately, there exists a way for local governments to significantly increase solar energy installations within their boundaries without bearing the cost: through policies that require citizens to install onsite solar energy systems or contribute funds toward offsite solar energy facilities as a condition to receiving building or subdivision approvals. Because developers and the purchasers of homes or spaces within their new projects bear most of the costs under these “solar mandate” policies, such policies can significantly increase local solar energy development activity with minimal government funding. This Guide describes how local governments can use solar mandates to increase solar energy development and seeks to assist local government officials in adopting such policies in their respective jurisdictions. Built upon the inventive policy efforts of a small handful of cities and counties throughout the country, and consistent with a scope of local building regulation that has existed for decades, the model code provisions accompanying this Guide can be a low-cost and politically feasible way for local governments to accelerate the growth of solar energy development within their communities.