How energy efficient are UPS systems?

Most modern transformerless uninterruptible power supplies can run up to 96% or more in terms of energy efficiency in full online mode if they have an IGBT-based rectifier and inverter. Some transformer-based UPS can achieved up to 96% if they use a high efficiency design transformer. The higher the efficiency the lower the running costs and addition to cooling load in the server room or datacentre environment.