This power inverter combines the function of voltage inverter and UPS (Uninterruptible Power Supply). The inverter converts the energy supplied by a battery 12VDC to 230VAC. The UPS part is composed of a battery charger and a switch. The battery charger can charge the battery from an AC power source 230V, the power utility or a power generator. The switch ensures the transfer between the inverter and the mains (or power generator). The inverter runs into Bypass mode when it is connected to the mains or a power generator, then it powers the loads from the mains (or generator) and simultaneously charges the battery. When an outage occurs in the mains, it switches to the battery in less than 10ms without any disruption to powered devices, of cause if the batteries are charged.