Customized hardware provides a generator sizing interface to the user for selecting individual loads that may be present at a particular facility of building. The hardware and/or generator sizing interface receives one or more load selections from the user and, in response, generates a single line diagram or a one line diagram for power flow analysis based on the load selections. The hardware and/or generator sizing interface accesses a database for power requirements for the load selections of the diagram. A List of potential generators or an optimal generator is identified based at least in part on the power requirement of the load selections.