This paper is an overview of the requirements for successful, efficient application of electronically controlled variable-speed drive to HVAC variable-volume pumping. The requirements for coordinating the generation and terminal equipment with the variable-volume transportation system are addressed. The effects of overdesign on the efficiency of the variable-speed system are commented upon, and methods of overcoming this common malady are addressed. The highest efficiency, variable-frequency drives are identified and guidelines published to aid in choosing the best drive for a particular application. Featured are a specification checklist, a transportation system energy evaluation procedure, and a straightforward discussion of efficient parallel pumping systems.