How to Determine the Power & Size of Generator Needed

Nov 28, 2023

When assessing generator rentals, many business owners make the mistake of basing their choice on price or brand alone, without really considering what their power needs are and what size generator would best fit those needs. By choosing the wrong size, however, you risk facing system failures and even complete shutdowns, caused by overloading the generator’s capacity, as well as damaging the equipment powered by it and even some serious personal safety risks. To make sure that you are getting a generator that is compatible with your operations and equipment, you need to either consult a certified electrician (preferable), or truly understand the generator sizing process.

Types of generators

Today’s modern market for power generators is rich in models ranging from as low as 5 kW to over 3 megawatts. While personal and small business power needs are usually satisfied with generators of up to 50 kW, larger businesses require far more potent industrial-size units. Your first concern in choosing the right generator to rent should be the purpose it is going to serve. Don’t look to save money on renting a unit that is not even designed to fit your industry’s power needs, as you may incur far greater costs in equipment damage or system shutdowns.

Sizing a rental generator to best suit your needs

Imagine the following scenario: you decide to rent a standby, emergency case generator for a construction project. You decide to pick a smaller one, since it will only be used on as needed basis and will not run all the time. Unfortunately, the primary generator fails and you head over to transfer all of your power needs to the new rental. Naturally, the smaller standby generator is quickly overloaded and the equipment starts to shut down unexpectedly, causing project delays and unforeseen costs. The moral? It doesn’t matter how long the generator will be used for. What is crucial is that it is able to accommodate all items that depend on power without reaching full capacity.

On the other hand, under-loading a rental generator due to incorrect sizing may also cause technical issues and additional costs. Ideally, the power generator should run at about 70% of its capacity, since prolonged periods of under-loading lead to carbon buildup and internal (bore) glazing, which in turn cause soot and residue clogging the generator’s engine. The resulting malfunctions of the power equipment, such as failure to start or reach full capacity when necessary, can be mitigated through installing a load bank, which is associated with additional investment. The problem can be avoided altogether by taking the time to understand your power requirements and settling on the correct size of rental generator for your specific needs.

Calculating your power requirements

In order to figure out how much power you actually need, you need to sit down and list all items used in your business or project that need to be powered through a generator. Next, you need to identify each item’s starting and running wattage and calculate how much power each of them needs in total. You can always have an electrician survey the equipment and perform these calculations for you, as well as recommend a generator size. If you prefer to do this on your own, locate the identification plates of each power-driven item to get the individual power requirements of each and arrive at a sum. Use an online converter to get both the kW and kVA measures, since these may sometimes differ depending on your equipment. Finally, determine whether you need to run a single or a 3 phase motor (or no motor at all) before you settle on the right size and type of generator.

Don’t hesitate to call us for a consultation if any of this seems too complex or you are not sure how to get started. Our trained specialists will help you determine the right size of generator for your business’ unique power needs. With models ranging from 20 kW to 2,000 kW, Trinity Power can supply a generator that is reliable and perfectly fits your operation’s power requirements.