A Step by Step Guide to Generator Sizing

Getting the sizing of your generator spot on is key. If you go too small, you’ll find yourself without enough power, but go too big and you’re wasting valuable money on energy you don’t need.

And if you’ve never dealt with generators before, it can pretty tough to know where to begin, so we’ve put together this step-by-step guide to generator sizing.

Calculate the wattage you need

First things first we need to assess what exactly it is that you’ll be powering with your generator.

Take into account everything you’ll be using the generator for, and add up the combined wattage.

The wattage should be available either on the equipment itself, or in its manual.

(If using equipment with an electric motor you’ll want to use the ‘starting wattage’ as opposed to the ‘running wattage’ as these are two separate measurements, and obviously you need to start up the machine before it can run!)

Generally speaking, anywhere from 5kW to 50kW can be handled by a small personal use generator, but for anything more than this you’ll require an industrial sized generator.

Convert to kilo volt amperes

Generators are sized using kilo volt amperes (kVA) instead of watts, so you’ll need to do a bit of maths unfortunately!

You should have your total combined wattage (in kilowatts) so you’ll then need to follow this simple formula:

Kilowatts (kW) / power factor (pf) = kilo volt amperes (kVA)

Wondering what power factor is? The standard power factor for generators is 0.8. So for example, if your equipment requires 600 kW, you would divide this by 0.8, which equals 750 kVA.

Define what you’ll be using the generator for

Whether you’re using your generator as a main power source or just as a backup will have an impact upon the size you’d be best suited to.

As a rule, generators should never be run at full power for any longer than half an hour. So if you’re using the generator as your primary power source, you’ll probably want to run one at between 70 and 80% capacity.

This will not only improve your generators performance, but it will also give you room to increase the power if needs to be.

Some people believe that if they’re just using their generator for standby power, then they can get away with just using a small generator, but this runs the risk of damaging both the generator and the equipment it’s connected to.

Check out your site

Now you should roughly know how much power you’re going to require and at what capacity, it’s time to start thinking logistics.

Make sure that a generator of the size that you’ll be requiring will be able to be housed on the site that you’re wishing to power.

If not, you might have to think about housing the generator somewhere off-site, or perhaps take multiple smaller generators.

Get in touch!

While we hope this guide has gone some way toward making generators seem a little simpler, there is no substitute for getting in touch with the experts!

Here at Event Electrix we will not only supply you with any generators that you might need, but are also happy to advise you on what solution best suits your needs.

We have over 20 years’ experience of bringing electric power solutions to events around the country, so we’re sure we can find something that will be suitable for you!