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What Size Breaker Do I Need for My Generator? (Explained)

Circuit breaker size is not universal. Different electrical instruments and machines require different sizes of breakers. But the most common sizes of breaker are 15,20,30, 40, and 50.

However, you will find breakers up to 6000 amps. But the question is what size breaker you need for your generator. We researched on that topic and found various answers. Mainly, it depends on generator capacity, but most of the standard sizes will meet the requirements.

We will look at different watts and suggest what size breaker will be suitable for what amount of power. Also, there is a shortcut way to decide the breaker’s size.

In a nutshell, it will be a one-piece write-up where you will find everything regarding breaker size and generators. Indeed, you will find the perfect breaker size for your generator.

What size breaker do I need for my generator?

You need a 40 to 50-amp circuit breaker for your generator if it comes in standard size power. Generators have different power capacities. Let’s say you have a 2500 watts generator; in that case, a 30-amp breaker would be a great fit. It will vary from device to device and will depend on the power.

3500 watts:

If your generator adjusted power is 3500 watts, you need a 30 amp 2 pole breaker. A 30 AMP breaker can support more than 3500 watts’ generator.

That’s why you should go for a 30 AMP size breaker for your 3500 watts generator. You don’t need to use a bigger size breaker. Also, try to avoid 20 or 25 size breakers in this regard.

5000 watts:

A 5000 watts generator will need a 35 AMP breaker. It’s a standard and safe size for this type of generator. You should avoid the advice if anyone asks you to use a 30 AMP breaker for 4500 to 5000 watts of power.

35 AMP is the right size for your 5000 watts’ generator. So, make your choice wisely and use the recommended size breaker.

5500 watt:

If you have a 5500-watt generator, you can go for either a 35 AMP breaker or a 40 AMP breaker. But, you cannot use a 30 AMP breaker; it will fail to serve its purpose.

However, a 35 AMP size breaker will be sufficient for a 5500 watts power generator.

7500 watt:

40 AMP 2 pole circuit breaker will perfectly match 7500 watts. That means, if you have a generator that comes with 7500-watt power, you should use a 40 AMP size circuit.

8000 watt:

If you go for a standard size breaker like an 8000-watt generator, you need to use a 45 AMP size breaker. But it is also possible to run generators up to 8000 watts with a 30 AMP circuit breaker. 

If you want to live safely, you should go for a 45 AMP size breaker.

9000 watts:

When you buy a 9000 watts generator, you must use a 50 AMP circuit breaker. It is a perfect size indeed. If you go for a 45 or 30 AMP circuit breaker, it will fail to run a massive generator.

That’s why you need a 50 AMP breaker for your 9000 watts generator.

9500 watt:

50 AMP breaker will be your best choice to run a 9500 watts generator. You don’t need to use any bigger size breaker. You can smoothly run a 9500 watts generator with a 50 AMP breaker. That’s why it is the standard breaker size.

10000 watts:

A 10000 watts generator must come with massive power. Therefore, you cannot use a 30 or 45 AMP breaker to run it. That’s why you need a 50 AMP breaker for your 10000 watts’ generator.

12000 watts:

If your generator cones with 12000 watts power that runs on 240 volts, you should go for a 50 AMP breaker. It is the correct size breaker that you can safely use for your generator.

13000 watts:

When you buy a 13000 watts generator, you may be advised to buy a 50 AMP breaker. The main reason is the high power capacity. And we know that a 50 AMP breaker can easily handle up to 15000 watts of power. 

That’s why you need a 50 AMP breaker.

What size breaker for portable generators?

A 30 AMP breaker will be the best choice for portable generators. Typically, portable generators come with standard power. It is not like a massive powerhouse. Therefore, you can use a 30 AMP size breaker for portable generators.

As we have described, a 30 AMP breaker can hold up to 8000 watts’ generator. If you have a portable generator of 3500 watts, you can still use the 30 AMP size breaker. You don’t need to go for the bigger size breakers.

On the other hand, if your portable generator is only 500 or 1000 watts, you can use a 15 AMP breaker. That means, if you have a bigger size portable generator, go for a big size breaker. In contrast, you should use a 10 to 15 AMP breaker when you have a small portable generator.

What is the generator breaker? Do generators have circuit breakers?

The generator breaker is a safety device that maintains the right electric flow and controls the voltage. It connects the generator to the network or electric power supply; the generator breaker will cut off the network if needed.

Mainly it works for safety purposes and to reduce short-circuit accidents. That’s why generators have circuit breakers. Significantly, the generator is a powerhouse.

It works with electric voltage. Sometimes, it may get the high voltage that it cannot support; then, the circuit breaker will separate the generator from the network and reduce the risk of short-circuiting.

How to size a breaker for a generator?

To size a breaker for a generator, you can follow these steps.

Read the user manual:

Read the complete user manual of your generator. Try to know about the exact KW and lag factor. This is your first step to size a breaker for a generator.

Get the rated current:

Now, you get the rated current and exact power. You need to divide the rated current by the power factor. You will get rated current from the generator specifications. You must know the rated current to get the breaker size.

Right breaker size:

Now you know the right breaker size. Let’s see that the rated current is 50 AMP, and the power factor is 0.8. In that case, the perfect size of the breaker would be 59/0.8 equals 62.5. That means you can use a 65 AMP breaker.

These are the three simple steps to size a breaker for a generator. You can follow these steps and ideally get the right size of your breaker.

How to install a breaker for a generator?

If you struggle to install a breaker in your generator, you can follow our tips and make it easier. There will be no more confusion and struggles.

Open the panel:

First thing first, opens the panel. You can use a screwdriver and open all the screws first. But the fact is that you need to turn off the electricity then open the screws.

Look for the switch option:

After opening the generator, you will see a part where you need to place the breaker. It will look like a switch option, but it should be empty.

Some generators come with proper indication signs that will assist you to find the right place.

Place in the required position:

Now, take your new breaker and place it in the required position. You can follow the user manual of the breaker. Then you need to join the wires.

There might be two different colors of the wires. One may come in red, and the other is black. Connect them with the generator wires.

Join the wires:

If you join the wires correctly, you are done. It’s time to close the opening panel. Make sure you place the opener with perfection.

Restart the generator:

It’s time to restart the generator. After that, your generator and breaker will be ready to use. You can run the generator and enjoy the service.

These are the simple steps to install the breaker in your generator. Nothing is hard or complicated. If you still find it challenging, you can take help from a generator engineer.

It would be better to go to a local electric shop and ask the shopper to install the breaker. However, most of the time, when you buy a new generator, the manufacturer may give you a free service.

If you are an expert and know-how to install breakers, you can follow these steps.

Final Thoughts

Perfect circuit breaker size depends on the generator’s rated current. But 30 amps might be the best size you need for your generator. However, you can easily calculate breaker size by dividing the rated current by the power factor. You can follow our steps and calculate the size.