Capacity expansion models (CEMs) help resource planners identify optimal resource planning decisions. How well these optimal solutions reflect company-specific implementation considerations can depend on input data and modeling choices. While some of these considerations may already be included by planners applying CEMs in practice, evolving trends related to the practical implementation of resource plans may further constrain the set of feasible portfolios. Additionally, determining which constraints to incorporate and identifying relevant data to support these assumptions can be challenging. Understanding these “realistic constraints” can be important for planning feasible portfolios and defining robust resource strategies. This research identifies key constraints relevant to today's resource planners through a landscape review of research sources and integrated resource plans from electric companies. It outlines concepts for incorporating these constraints into CEMs and provides data considerations for two specific examples: deployment timelines for new resources and siting constraints.