Which LEED credit encourages projects to implement energy-efficient lighting?

The credit that encourages projects to implement energy-efficient lighting is "Optimize Energy Performance." This credit is fundamental in LEED as it focuses on improving the overall energy efficiency of a building or project. It encourages the use of strategies and technologies that significantly reduce energy consumption, which includes energy-efficient lighting solutions.

By optimizing energy performance, projects are prompted to not only consider the lighting systems but also the integration of daylighting, advanced lighting controls, and other innovative technologies that can enhance energy efficiency. This approach assists in lowering operational costs and minimizing the environmental impact, aligning with LEED's goals to promote sustainability and resource efficiency.

In contrast, the other options do not specifically address energy-efficient lighting practices. "Water Efficiency" focuses on reducing water consumption, "Indoor Environmental Quality" pertains to indoor air quality and occupant comfort, while "Materials and Resources" deals with sustainable materials usage and waste management. Thus, these areas do not directly encompass the intent behind energy-efficient lighting strategies.