What Size Generator for 100 Amp Service? An Ultimate Guide
Need to know what size generator for 100 amp service? Our guide provides expert advice to help you select the right generator for your home or business.
When it comes to 100 amp service, choosing the right size generator is crucial for ensuring that you have enough power during power outages.
A generator that’s too small won’t be able to handle the load, while a generator that’s too large will be expensive, heavy, and difficult to move around.
According to a report by Grand View Research, the global market size of the generator set is expected to reach USD 32.5 billion by 2025.
This growth can be attributed to the increasing demand for continuous and reliable power supply from various industries, including residential, commercial, and industrial sectors.
Moreover, the report also highlights that the increasing frequency of power outages and natural disasters is expected to boost the demand for backup power sources like generators.
The size of the generator required for a 100 amp service depends on the total electrical load that needs to be powered during a power outage. Typically, a generator with a capacity of 20,000 to 22,000 watts is enough for powering a home with a 100-amp service panel.
In this article, we’ll take a closer look at what size generator you need for 100-amp service and discuss some essential factors to consider when making your decision.
How to Size a Generator for a 100-Amp Service?
To size a generator for a 100-amp service, you need to determine the total electrical load that the generator will need to power during an outage.
This involves calculating the combined wattage of all the essential appliances and equipment that you need to run, including lights, refrigerators, HVAC systems, and other critical electrical loads.
Once you have the total wattage, add 20% to the final number to account for any starting surge requirements. This final number represents the minimum wattage required for your generator.
For example:
If the combined wattage of all essential appliances and equipment is 16,000 watts, adding 20% would give you a minimum wattage requirement of 19,200 watts.
A generator with a capacity of 20,000 to 22,000 watts is generally enough for powering a home with a 100-amp service panel.
Generator Sizing Consideration for 100 Amp Service?
1. Electrical Load:
For 100 Amp Service, the electrical load can range from 12,000 to 24,000 watts, depending on the specific electrical appliances used.
To calculate the electrical load, you will need to add up the wattage of each appliance you want to power.
You can find the wattage rating of each appliance on its nameplate or in the owner’s manual. Or you can use Ohm’s law as well.
WATTS = AMP x VOLTS
Once you have added up the wattage of all the appliances, you can select a generator that can provide at least that amount of power.
2. Starting vs. Running Wattage:
Starting, peak, or surge wattage is the amount of power required to start an appliance.
Running, rated, or continuous wattage is the amount of power required to keep the appliance running.
Appliances such as refrigerators, air conditioners, and well pumps require a higher starting wattage than running wattage to overcome inertia to start properly.
3. Voltage and Amperage:
Another consideration when selecting a generator size is the voltage and amperage of the electrical service.
For 100 Amp Service, the electrical service provides 240 volts with two hot wires and a neutral wire.
The amperage rating represents the maximum current that the electrical service can provide. In this case, the maximum current is 100 amps.
4. Safety:
It’s important to select a generator size that is safe to operate and won’t overload the electrical system.
Overloading the electrical system can cause damage to the appliances or create a safety hazard. Overheating is another hazard that causes fire and explosion.
If you’re unsure about the appropriate generator size, it’s best to consult with a licensed electrician to determine the electrical load and generator size required for your specific needs.
Recommended Read: What size generator do I need for a 50 amp RV?
Understanding the 100 Amp Service
1. What is a 100 Amp Service?
The 100 Amp Service is an electrical service that provides a maximum current of 100 amps.
This type of service is common in residential homes and can provide enough power for typical household needs. We also have written a detailed guide about selecting the right-sized generator for households.
2. Voltage:
The 100 Amp Service typically provides a voltage of 240 volts with two hot wires and a neutral wire.
The voltage is the electrical potential difference between two points in an electrical circuit, and it determines the amount of electrical work that can be done by the system.
3. Amperage:
The amperage is the maximum current that the electrical service can provide. For 100 Amp Service, the maximum current is 100 amps.
The amperage is important to consider when selecting electrical appliances and devices, as they must be rated to handle the amperage of the electrical service.
4. Electrical Load:
The electrical load is the amount of power required to run all the electrical appliances and devices in a home.
For 100 Amp Service, the electrical load can range from 12,000 to 24,000 watts, depending on the specific electrical appliances used.
5. Circuit Breakers:
The 100 Amp Service typically uses circuit breakers to protect the electrical system from overload and electrical faults.
Circuit breakers are designed to automatically disconnect the electrical supply when the current exceeds a certain threshold, which helps prevent damage to the electrical system and reduces the risk of electrical fires.
Recommended Read: What Size Portable Generator to Power 200 Amp Service?
Is 12KW Generator Good for 100 Amp Service?
Let’s explain this question by giving some examples.
Example 1:
Assuming a power factor of 1.0 (unity), a 12000-watt generator would provide a maximum current of:
Current (amps) = Power (watts) / Voltage (volts)
Current (amps) = 12000 watts / 240 volts
Current (amps) = 50 amps
This generator would be suitable for powering a 100 Amp Service with an electrical load of up to 50 amps. However, keep in mind that starting wattage for some appliances may require a larger generator.
Example 2:
Assuming a power factor of 0.8 (typical for many electrical loads), a 12000-watt generator would provide a maximum current of:
Current (amps) = Power (watts) / (Voltage (volts) x Power factor)
Current (amps) = 12000 watts / (240 volts x 0.8)
Current (amps) = 62.5 amps
This generator would be suitable for powering a 100 Amp Service with an electrical load of up to 62.5 amps.
Again, it’s important to factor in the starting wattage for some appliances when selecting a generator size.
Example 3:
Assuming a power factor of 0.8 and an electrical load of 24,000 watts, a 12000-watt generator would not be suitable for powering a 100 Amp Service.
In this case, the electrical load exceeds the maximum output of the generator, which would result in an overload condition and could damage the appliances or the generator.
What Appliances You Can Run Using 100 Amp service?
| Appliance | Starting Watts | Rated Watts |
| Air conditioner (10,000 BTU) | 2,200 | 1,500 |
| Clothes dryer (electric) | 5,500 | 5,500 |
| Clothes dryer (gas) | 2,200 | 700-1,800 |
| Dishwasher | 1,200 | 1,200 |
| Electric oven | 5,600 | 5,600 |
| Freezer | 800 | 800 |
| Furnace fan (gas) | 300-700 | 300-700 |
| Hair dryer | 1,500-1,800 | 1,500-1,800 |
| Microwave | 800 | 800 |
| Refrigerator | 800 | 800 |
| Toaster | 1,200 | 1,200 |
| TV (LCD) | 120 | 120 |
| Vacuum cleaner | 750-1,200 | 750-1,200 |
| Washing machine | 1,200 | 1,200 |
What are the Best Generators for 100 Amp Service?
| Generator Model | Rated Wattage | Max Current (Assuming 1.0 power factor) | Max Current (Assuming 0.8 power factor) | Outlets | Run Time (at 50% Load) |
| Generac GP12000E | 12,000 watts | 50 amps | 62.5 amps | 5x 120V 20A GFCI Outlets, 1x 120V/240V 30A Twist-Lock Outlet, 1x 120V/240V 50A Outlet | 11 hours |
| Briggs & Stratton 30675A Q6500 | 6,500 watts | 27.1 amps | 33.9 amps | 4x 120V 20A Outlets, 2x USB Outlets | 14 hours |
| Westinghouse WGen7500 | 7,500 watts | 31.25 amps | 39.1 amps | 4x 120V 20A Outlets, 1x 120V/240V 30A Outlet, 1x 120V/240V 50A Outlet | 16 hours |
| Champion 100294 | 7,500 watts | 31.25 amps | 39.1 amps | 4x 120V 20A Outlets, 1x 120V/240V 30A Outlet, 1x 120V/240V 50A Outlet | 8 hours (Gasoline), 5.5 hours (Propane) |
| DuroMax XP12000EH | 12,000 watts | 50 amps | 62.5 amps | 2x 120V 20A Outlets, 1x 120V/240V 30A Twist-Lock Outlet, 1x 120V/240V 50A Outlet | 9 hours (Gasoline), 4.5 hours (Propane) |
Recommended Read: What Size Generator For 400 Amp Service?
Frequently Asked Questions (FAQs)
How Do I Calculate the Electrical Load for a 100 Amp Service?
To calculate the electrical load for a 100 Amp Service, you will need to add up the wattage of all the electrical devices you plan to power, including lights, appliances, and other electrical equipment. You can then use a wattage calculator or consult with a licensed electrician to determine the appropriate generator size.
Why Power Factor is Important to Calculate for a 100 Amp Service?
Power factor is a measure of how efficiently electrical power is used in a circuit. When selecting a generator for a 100 Amp Service, it’s important to consider power factor because some electrical devices, such as motors and other inductive loads, can require a higher amount of starting wattage than their rated wattage
Can I Use a Portable Generator for a 100 Amp Service?
You can use a portable generator for a 100 Amp Service, but it’s important to select a generator that is rated for the appropriate wattage and has the necessary outlets for your specific needs.
What Size Generator for 100 Amp Service?
A generator for 100-amp service typically requires a 12,000W to 20,000 watts of power output. However, the exact size of the generator needed will depend on the specific electrical requirements of the home or business. It is recommended to consult with a licensed electrician to determine the appropriate size generator for your specific needs.
Fareed, the highly skilled electrical expert, boasts 5 years of extensive experience in proficiently maintaining, repairing, diagnosing, and installing a diverse range of electrical systems.