Vapor injection has been available on large commercial screw and multistage centrifugal compressors, but not on small hermetic compressors. The recent introduction of vapor-injected scroll compressors allows the economized refrigeration cycle to be applied with individual small compressors, and achieve the benefits of increased capacity and efficiency. This article describes the economized vapor-injection (EVI) scroll compressor concept, its key components, and the associated performance and application aspects for commercial refrigeration systems.