Critical Power Exchange Buys and Sells Used Diesel Generators, Used Air Conditioners, Surplus, Refurbished and, Used Data Center Cooling, UPS Systems, PDU's, Transformers, Fire Suppression and Raised Flooring. We are your premier source for used backup power, surplus backup power and surplus power equipment, and data center power equipment. Since 1993, Critical Power Exchange has been YOUR NUMBER ONE SOURCE for used backup power and environmental equipment for mission-critical data centers.