A 9000 watt generator is theoretically maximum 75 amps at 120 volts and 37.5 amps at 240 volts.
However, the Watts = Amps x Volts formula is not always enough for reality. The outlets of a generator can limit the number of amps too.
Many 9000 watt generators “only” have 30 amp outlets. These are only able to produce 30 amps.
On the flip side, there are also 9000 watt generators with 50 amp outlets. 50 amps would be the maximum number of amps these machines produce.
When it comes to what size breakers you want to use for these machines it depends on what you want to protect.
If your electrical circuit can only deal with 30 amps, you need this size of breaker even though your 9000 watt does not reach its potential.
How many amps can a 9kW generator theoretically produce?
A 9 kW generator can theoretically produce 75 amps at 120 volts and 37.5 amps at 240 volts.
You get these numbers by filling in the Watts = Amps x Volts formula and using a calculator.
However, when investing in and using a 9000 watt generator this is not the entire story.
How many amps can a 9000 watt generator actually run?
A 9000 watt generator can often actually only run 30 amps. There are also 9000 watt generators that can run 50 amps.
The reason that the formula above is not enough is that generators, including the 9000 watt models, come with different outlets.
These outlets (and sometimes breakers) also put a limit on how many amps a 9000 watt generator can actually run.
9000 watt generators actually “only” have 30 amp outlets a good amount of the time.
On the other hand, you should also have no issues finding 9000 watt generators with 50 amp outlets (which are still not enough for the theoretical 75 amps at 120v).
Whether you need a 30 amp or 50 amp generator depends on what devices you want to run.
Many appliances and tools will only need 30 amps but bigger electrical systems like central air conditioning could need 50 amps to function.
What size breaker do you need for a 9000 watt generator?
You need a 30 amp size breaker for a 9000 watt generator if your electrical circuit can only deal with 30 amps and to make sure your machine can not overload.
However, there are many situations with more nuance.
Circuit breakers are devices that cut off the electrical circuit when too much power goes through.
The first reason these are useful is that they protect your electrical circuit since this can only handle a certain amount of amps.
Secondly, breakers can help you avoid overloading your 9000 watt generator.
What size breaker you need for a 9000 watt generator depends on what you want to protect the most.
If you know your electrical circuit can deal with fewer amps than the 9000 watt generator can provide, you want a breaker of this size. For example, 30 amps.
On the other hand, to stop your 9000 watt generator from overloading you would choose breakers that trigger at somewhere between 37.5 to 75 amps depending on how many volts you plan to use.
For example, if you plan to use 240 volts, you would need a 37.5 amp (or a more common 40 amp) breaker for your 9000 watt generator.