Methods of manufacturing a direct current (DC) uninterruptible power supply (UPS) configured as an intrinsic power transfer switch are provided. One method includes providing multiple inputs, multiple rectifiers coupled to the inputs, a common node coupled to the rectifiers, and at least one DC output coupled to the common node. The DC output(s) is/are adapted for connection to at least one electrical load and a first input is adapted for connection to a first electrical service. A second input is adapted for connection to a second electrical service, the DC UPS continuing to supply power to the at least one electrical load in the event of a loss of either the first or second electrical services. Also provided are methods of manufacturing an intrinsic power transfer switch for a high-power electrical load requiring at least two electrical service inputs.