Scaling-up electrochromic windows from the lab to buildings and grid integration

Electrochromic (EC) windows can regulate solar heat and daylight, yet laboratory performance alone does not determine their value in buildings. This Review traces electrochromic technology from materials and device architectures through scale-up and commercialization to building operation and grid interaction. It examines how useful function is filtered by large-area uniformity, durability, sealing reliability, manufacturing yield, cost, and control. These constraints explain why mature products still favor conservative inorganic solid-state platforms despite rapid advances in dual-band and multiband devices. The analysis further shows that optical states should be defined by application needs before materials and devices are optimized to deliver them, linking spectral design to comfort, energy, and flexibility objectives. Because most reported grid-responsive benefits remain simulation-based, future studies must separate projected potential from field-verified performance. Progress therefore requires application-driven design, scalable qualification, and real-world validation that preserve useful function from material discovery to reliable building operation and verifiable grid services. This Review discusses electrochromic technology from materials and device architectures, scale-up and commercialization, to building operation and grid interaction. It also examines how useful function is enabled by large-area uniformity, durability, sealing reliability, manufacturing yield, cost, and control.