This paper, which was written jointly by RMI and the Department of Energy, describes the energy efficiency measures undertaken by eight organizations. In each of the cases presented, improved efficiency in lighting, heating, and cooling increased worker productivity, decreased absenteeism, and sometimes improved the quality of the work being performed. While increasing the worker experience was not the original goal in most of the cases, it was an unexpected benefit for the organizations. The case studies in this paper demonstrate that energy efficient retrofits for existing buildings and new buildings designed for energy efficient performance can have substantial economic returns. Several case studies of retrofits are presented: a retrofit of the Post Office in Reno, Nevada, which, with energy savings and resulting worker productivity, was able to pay back the costs of the retrofit in less than one year; a Boeing assembly space that designed energy efficient lighting in order to save energy costs and improve worker safety; a blade manufacturer that installed a new type of lighting that saved energy costs and improved operators’ ability to perform their tasks; an electric utility that improved their in-house lighting system and decreased absenteeism related to eyestrain and headaches. Several case studies of new buildings are also presented: a new office building for Lockheed Boeing was designed for deep daylighting by installing large window walls, light shelves, and an atrium.