EPS and UPS both have mains bypass and inverter circuit, its function difference is: EPS only functions with continuous power supply, the inverter switching time is generally less demanding (application for special occasions with certain requirements), how can output and the output of the brightest and surveillance detection function with a single battery, the daily focus on bypass, when mains power supply into the inverter, high power utilization. The UPS (on-line) is just the way the total output, generally emphasize its three functions: (A) frequency stabilization (B) for the switching time demanding uninterrupted power supply (C) purifying mains, daily focuses rectifier / double conversion circuitry inverter, inverter failure or overload when turned bypass, energy efficiency is not high (generally 80% -90%). However, in Europe and supply more complete grid of the country, for energy conservation, the use of part of the UPS inverter has been switched places replaced by a very short time (less than 10 milliseconds) of EPS.