EngineerBenchEstimating running and startup electrical demand
A workshop load estimate separates equipment that can run together from equipment that is present but idle. Enter each load's power, quantity, and simultaneous-use fraction. The running total reflects those assumptions; the startup estimate adds the largest single entered motor-starting increment.
Use electrical input power
A motor's shaft output is not necessarily its electrical input. Use measured input or suitable manufacturer data for the power field. Match the supply selection and voltage to the system being estimated before interpreting the current result.
Check the startup assumption
This estimate does not model several motors starting together or voltage recovery during a start. It is useful for comparing operating scenarios, but it is not a service-load calculation to an electrical code. Branch circuits, protective devices, and supply suitability require separate checks.
Building a realistic operating scenario
Start with a list of equipment that can operate at the same time: a machine, its extraction system, lighting, and any supporting equipment may form one scenario. A different combination may govern another part of the day. The simultaneous-use fraction scales an entered load in this worksheet; it does not model the probability of overlap or replace a prescribed demand factor from an electrical design method.
Check whether each rating is electrical input, mechanical output, or an apparent-power figure before entering watts. Quantities multiply the load contribution, so avoid putting a combined total in a row and then multiplying it again by the number of machines. The starting estimate considers the largest single increment under its stated assumption. If two machines can start together, evaluate that condition separately with an appropriate model. A generator or inverter must meet voltage, frequency, transient, and load-type requirements as well as the running-power total, so use the result to describe demand rather than to approve equipment.
Formula
Running demand sums equipment power × quantity × simultaneous fraction. Startup adds the largest single motor increment.