Aspects of the invention are directed to systems and method for limiting losses in an uninterruptible power supply. In one aspect, the present invention provides an uninterruptible power supply (UPS) comprising an input to receive input power having an input voltage, an output to provide output power having an output voltage, a neutral line, an automatic voltage regulation (AVR) transformer coupled to the input and the output of the UPS and having an input, an output, a core and at least one switch controllably coupled to at least one of the core, the input and the output, and a means for isolating the core of the AVR transformer from the neutral line when the input voltage is substantially equal to a defined output voltage.