Portable generators are a great way to power everything from a campervan to a major worksite. Modern generators are available in thousands of different sizes, and it’s possible to hire generators that are perfectly matched to any requirement. But choosing the right generator size is critical. An oversized generator will be costly to hire and expensive to run, meanwhile, an undersized generator won’t be able to keep up with the demand. If you need to make sure your generator provides the power you need, we’re going to go over how to choose the right size for 3 phase generator hire.
How to Determine Generator Size
The size of the generator you need is directly proportional to how you want to use the device. For example, if you want a generator that can run a microwave in your campervan, you’ll only need a small unit. But, if you want a generator that can run industrial speakers at a concert, you’ll need a much bigger power supply
To determine the right generator size, we need to check how much power is consumed by the equipment that will be attached to the generator. This information is usually printed on a tag that’s attached to the appliance or to its power cable. As an example, we’ll calculate what size generator you’d need to run the appliances in a campervan:
| Appliance | Running Power | Starting Power |
| Toaster | 150W | 600W |
| Fridge | 750W | 750W |
| TV | 200W | 200W |
| Fan | 60W | 180W |
| TOTAL | 1160W |
You’ll see here that we’ve listed two different power figures for each device. The “Running Power” is the average amount of electricity that’s consumed while the appliance is in use. The “Starting Power” is the amount of electricity that’s consumed when the appliance is first turned on. Starting Power is often higher than Running Power, especially for appliances that contain motors and heating elements.
Calculating the Right Generator Size
If we continue our example from above, we now have everything we need to figure out what size generator we’ll need to buy for our campervan. To calculate the minimum generator size, we take the total Running Power and add the largest Starting Power figure:
1160W + 750W = 1910W
That means we need a generator which can produce a minimum of 1910W. But it’s not quite that simple, because generators don’t like to operate at full capacity all the time. Remember that generators are small engines. You wouldn’t rev your car to the limit constantly, so you shouldn’t overload your generator either. A good rule of thumb here is to add an extra 20% to your total power consumption:
1910W x 1.2 = 2292W
The extra 20% protects the generator from being overloaded, which means your appliances will always be running. So, in this case, we’d need a generator that produces approximately 2300W of power. If you can’t find a generator that’s exactly the right size then it’s always a good idea to opt for the larger option. A slightly oversized generator will perform much better than a slightly undersized generator.
Single vs Three-Phase Generators
The next question is to figure out whether you need a single-phase or three-phase generator. The number of phases produced by a generator refers to the way the electrical load is distributed. Single-phase generators produce normal Alternating Current (AC) electricity that’s suitable for most household appliances and hand tools. Single-phase power is generated at 240V and provides a maximum of around 100 amps, although it’s typically supplied at much lower current.
For more demanding loads, you may need a three-phase generator. Three-phase generators produce AC electricity at much higher voltages and currents. Depending on your needs, a three-phase generator can produce electricity at up to 400V, which is ideal for things like welders, commercial equipment, industrial machinery and permanent power backups.
You’ll usually need a three-phase generator if you’re looking to operate a large worksite, provide backup power or need electricity for a large event. The added benefit of three-phase generators is that they’re also capable of producing single-phase power, so you can hook up all your equipment to a single generator.
Why It’s Important to Calculate the Right Generator Size
Your generator keeps your appliances, tools and equipment online. Even still, many people are tempted to save a bit of money by choosing an undersized generator and making do. Especially when hiring generators, customers often opt for the smaller size and hope for the best. But choosing the right generator size is critical, and it can save you from:
- Generator faults and breakdowns due to overload
- Damaged equipment
- Safety risks from equipment failure
- Premature generator failure
Undersized generators also have higher maintenance requirements and are more expensive to run. If you’re operating a large worksite or power backup, those additional costs can be significant, which far outweighs the initial savings.
