In accordance with presently disclosed embodiments, uninterruptable power supplies and a method for detecting power failures for a UPS are provided. In one embodiment, the method comprises: detecting at least a portion of a waveform of a primary power input of an uninterruptable power supply; calculating at least one of a detected voltage value and a detected current value, based, at least in part, on the detected waveform by calculating at least one of a root mean square, an average, or a summation of the detected waveform; and transferring the uninterruptable power supply to a secondary power input in response to at least one of the following conditions: the detected voltage value is lower than a minimum threshold voltage value, the detected voltage value is higher than a maximum threshold voltage, or the detected current value is higher than an over current value.