Your Step-By-Step Guide To Generator Sizing

Your Step-By-Step Guide To Generator Sizing

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It’s important when selecting a generator, that you choose one that’s the right size to meet your power requirements. Buy or hire a generator that’s too big, and you risk wasting money; buy or hire one that’s too small, on the other hand, and you won’t be able to power your equipment. 

Whether a 50 kva generator, or a 100 kva generator, size matters, and to help you get it right, here is a step-by-step guide:

Begin by calculating the load size

Make a list of everything you need to provide power to, and calculate the total wattage. Wattage information can be found either on the equipment itself, or in the manufacturers guide. 

Then convert kW to kVA – sounds simple, but you may need expert guidance!

Once you’ve added up the wattage required for your equipment, you’ll arrive at the total power needed in kilowatts, or kW. 

Rated in kilo-volt-amperes, or kVA, this is a measure of a systems apparent power, and in a 100% efficient system, kW simply = kVA. However, most electrical systems aren’t that efficient, meaning that not all of the systems apparent power will be used to produce a useful work output. Expressed between 0 and 1, electrical efficiency can be used to convert between kVA and kW; the closer the power factor is to 1, the higher the level of conversion efficiency. 

When rated using international standards, generators have a power factor of 0.8, and it’s essential that this be used to correctly match the size of the load to the right generator. If a generator rated at 100kVA with a 0.8 power factor, will not be sufficient to power something with a 100kW power requirement.

With this in mind, if your piece of equipment has a total wattage of 100kW, the smallest generator to match those needs would be a 125kVA. 

If you’re struggling to get your head around kVAs and kWs, don’t worry, you’re not alone! To explain it in more detail, try asking a reputable generator manufacturer or supplier.

Next, define what your running requirements will be

Did you know that a generator shouldn’t be operated at maximum capacity for more than half an hour? This means that if your generator hire is going to be your primary power source, you’ll need to size for 70-80% capacity. This will not only improve performance, but leave a safety margin of 20-30% for any future power requirements you might have. 

Finally, check that your power requirements are workable given the conditions and location of your site

How a generator is delivered to you, offloaded and maneuvered into position, will be largely dependent on where it’s going to be placed. You’ll need to check whether there’s adequate access to the site for the vehicle not just to approach, but to offload the generator safely and get it into position. Keep in mind that a crane may be needed for larger generators. 

For further information about choosing the right generator to meet your power needs, it’s recommended that you consult with a certified electrician. 

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