Load factor is the ratio of your electric energy use in kilowatt-hours to your peak demand in kilowatts. For reactive loads: Wattage = amperes x volts x load factor.For resistive loads (most common type): Wattage = amperes x volts.Calculate your total power requirement by adding up these kW or KVA figures.įor equipment rated in amperes, you can convert amps to watts with the following formula:.These figures are typically inscribed somewhere on the equipment itself, as well as recorded in the owner’s manual. Determine the starting wattage (energy needed to turn it on) and running wattage (energy needed to operate it) for each piece of equipment.Form a list of all items that will be powered.The basic generator sizing formula goes like this: This is the case whether it’s regarding primary power supply or emergency back-up power generation.

Office buildings, manufacturing facilities, data centers, and building complexes such as shopping malls, educational institutions, and living centers all require larger-capacity generators. Larger business and industrial applications obviously require more capacity and thus often utilize three-phase motors for higher power. Industrial generators are available in a range of sizes, from around 20kW to well over 3MW. These generators typically use a single-phase current, which are sufficient to power smaller equipment that don’t require constant, high-voltage power. These sizes run from 2kW-2000 watts or less for a recreational unit, up to about 50kW for a whole-house standby generator. If you’re a homeowner looking for backup or standby power, you need either a small, portable generator or a stationary standby generator. You should already have an idea of what class of generator you need. We’re laying those out in this guide to help you know how to determine what size generator you need. However, if you opt to do it yourself, you can still make an informed generator purchase or rental by following a few basic guidelines. To answer that last question, your first and best option is always to consult a certified electrician to assess your specific needs. It’s also something most consumers don’t do very often, so there’s a lot of confusion around which fuel type to use (diesel, natural gas, propane), which brand is best (Caterpillar, Cummins, MTU, Generac, Kohler, HIPOWER), and most especially, what size generator is appropriate. Buying a generator is typically a significant investment for a home or business owner.

Generator sizing guide