What Size Generator for 400 Amp Service

Choosing the right Generator for your power needs is critical to its durability and lifetime. However, the technical calculations involved make it confusing. Oversizing will lead to fuel wastage while under-sizing will cause overloading. This article explains how you can calculate and select the right Generator size for the best 400 Amp service.

Determining What Size Generator for 400 Amp Service

1. Understanding your power needs

Your power needs influence the size of the Generator required. A 400 Amp service Generator has a wattage output of 96000 watts and a voltage of 240 volts. It can light your home or a medium-sized building and power electronics in your home and medium-sized buildings.

Appliances like televisions have a voltage rating of 120 volts while heavier electronics like fridges, saunas, hot-tubs, dish-washer, and ovens require up to 240 volts.

You can confirm the power rating of your appliance by examining its packaging or stickers placed on it.

2. Calculating your power requirements

Generator capacities are measured in Kilowatts. To get the right power rating for your Generator, calculate the wattage you need then convert it to kiloWatts.

To find the wattage, multiply the current (400 Amp) and the voltage (240 Volts); 96000 Watts. Alternatively, you can use an online calculator. Input the current and voltage and it will convert them to Watts.

Since 1 kiloWatt equals 1000 Watts, divide the result by 1000 to convert to kiloWatts; 96 kW.

Alternatively, you can use an online calculator. Input the current and voltage and it will generate the kiloWatts required.

This is the net capacity in kiloWatt you need – but should not get.

3. Selection Criteria

For durability and long life, you should select a Generator that can handle 100% of your power needs while functioning at 90% efficiency. Alternatively, you can go for one whose capacity is 25% higher than the required capacity.

This will ensure maximum output for long hours and reduced wear and tear. It will also prevent your Generator from tripping or breaking down. Undersized Generators have an unstable frequency and voltage output. This can damage your appliances

Following the above criteria, a 120kW Generator will be the best option.90% of this capacity is 108kW; 12kW higher than the required rating. This extra 24 kW prevents your Generator from capacity overload when the power usage is higher than usual.


For a 400 Amp service, you require a 120 kilo Watt Generator. , go for a 120kW Generator. The excess 24kW will increase its lifetime and durability while preventing overloads and breakdowns.

The heat and noise emitted are also lesser making it the suitable choice.

Frequently asked questions (FAQ)

How Many kiloWatts’ Generator do I need for a 400 Amp service?

A 400 Amp service requires a 96 kiloWatt Generator at 100% output. A 120 kiloWatt Generator for maximum performance and output.

What size of Generator do I need for a 600 Amp service?

Assuming the maximum voltage for your use is 240V, the net wattage is [600*240] =144000 watts. Convert that into kilo Watts’s results in 144kW. For better performance, a Generator with a 25% more capacity; 180kW is recommended for a 600 Amp service.

How big of a Generator do I need for a 200 amp service?

At 240 volts and 200 Amps, the net required kilowattage is 48kW. The gross kiloWatts will be 60kW; the size of the Generator required for a 200 Amp service.

How many watts can a 400 amp service handle?

what size generator for 400 amp serviceMultiply the current output (400 Amps) by the voltage output of 240 Volts, it can handle 96,000 watts at 100% efficiency.

This can power your Fridge, Sauna, Bathtub, dishwasher, and laundry machine.

How much is a 400 amp service?

Setting up a 400 Amp service will cost you between $1,500 and $4, 000.However, this depends on your electricity provider or contractor and permit fees.

How many volts is a 400 amp service?

A 400 amp service has a maximum voltage of 240 Volts and a minimum voltage of 120 Volts.

How do you wire a 400 amp residential service?

You will require a 250 kc-mil gauge copper wire or a 350kc-mil Aluminum wire, a large service panel, a 2.5 inch PVC material conduit, and a circuit breaker in case you have fitted a fuse in your residence.

  1. Drop the copper or aluminum cable housed in the conduit system to the ground.
  2. Channel the cable through a tunnel in the ground.
  3. Connect it to the power distribution service panel. Ensure your service panel is SR-452 certified.
  4. Using well-insulated cables, connect appliances and lights to the service panel through power outlets in your home.

How do you split a 400 amp service?

At the main meter box, install two split-bolt 200 Amp feeders in the service panel containing the main circuit breakers.

To split the service, connect the feeders to separate 200 Amp service sub-panels.

Is there a 300 Amp service?

No. Electricity companies offer 200 Amp and 400 Amp as the standard services .However some like Phoenix offer an exception of 320 Amp for special circumstances.

How Do I upgrade my 400 Amp service?

When your circuit breaker starts to trip a frequently-a sign of overloading, request an inspection by an electrician from your electricity provider. If necessary, they will recommend an upgrade.

You will then submit a formal request for an upgrade to your electricity provider. Alternatively, you can contract a private provider. Be sure to obtain all the permits and licenses required depending on your state.

How wide is a 400 Amp panel?

The 400 Amp service panel is between 22 and 24 meters wide.

How Can I tell if I have a 400 Amp service?

Check the labeling on the main circuit breaker. There will be an Amperage rating of between 50Amp and 400 Amp. Your 400 Amp service will have the main circuit breaker with a 400 Amp amperage label.

Can you have more than 200-amp service?

Yes. You can have a 400 Amp service but a 300 Amp service is not available.

How much is a 400 Amp Service Upgrade?

A 400 Amp service upgrade will cost you between $ 1500 and $ 4000. This depends on your electricity provider and the price of equipment. The distance between your home and electrical poles can also impact the overall cost.

Video About 400 Amp Service

About Steve Stuart

Steve Stuart is an electrical engineer who developed interest on generators during his school years. After school, he became a generator enthusiast. This is after encountering power supply problems at the area of residence where he lived. Power would be on and off and so food would go bad and the room heater would go off especially during winter. After trying the different generator brands for several years, Steve now provides information on the available brands and products in the market today. Based on his experience, he gives the do’s and the don’ts when it comes to generator use.

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