What Size Portable Generator to Power 200 Amp Service?

The average electrical service for residences in the US ranges between 100 and 200 amps. What size generator for 200 amp service do you need? A portable generator of 15 to 20 kW is needed to supply power for this requirement. Choosing the correct size of the generator is important because both undersized and oversized generators create various issues. Let’s identify all the important details about finding the ideally sized generator for your domestic use.

what size generator for 200 amp service

How Many Watts Do You Need For a 200 Amp Panel?

The power output of a generator is measured in watts, which is the product of amps and volts. Checking the watts is necessary to ensure that the generator can supply a 200 amp service for your requirements. Houses are usually provided with a single-phase electrical service of 120/ 240V delta. Although a 200 amp single phase residential electrical service can handle up to 48,000 watts of power, it is recommended to use only 80% of the load for safety concerns. Thus, the safe load for a 200 amp electrical service is 38,400 watts.

You can easily calculate the demand for the circuits at your home. The voltage rating can be found in the panel next to the breaker. The amperage will also be indicated on the breaker.

What To Look Before Buying A 200 AMP Service Generator?

Buying a generator is not an easy task since there are many options to select from. You need to have a proper idea on the matter, especially when you decide on what size generator 200 amp service you need. Checking the following factors will help you in selecting a 200 amp service generator.

Fuel Tank Capacity

The capacity of the fuel tank is an important feature as you don’t want the power generation to stop abruptly due to insufficient fuel supply. Make sure to add a fuel stabilizer and additive when filling up your tank for the first time. This helps to secure the fuel from contamination and rapid temperature changes, especially during cold seasons. You can find fuel tanks as either portable or stationary. The portable fuel tanks are more convenient whereas the permanent tanks need to be installed permanently at the premises.

Transfer Switch

The transfer switch is the main component that makes your generator an uninterrupted power supply (UPS). When the grid power goes down, the transfer switch will transfer the load on the generator and supply power to your house. All you need to do is to plug the generator into the outlet connected to the transfer switch. If there is no transfer switch, you will have to connect all appliances at home to the generator using extension cords. A transfer switch should have a rating equal to or higher than the wattage of your generator. i.e., a 7000-watt generator needs to have a 7 kW transfer switch.

Portable or Stationary Generator

Decide on whether you need a portable or a stationary generator. If you need to move the generator to various locations, you should go for a portable generator. This is ideal if you only need it as a backup power source in emergencies. A stationary generator will have to be installed permanently in your yard. The advantage of this is that you don’t need to worry about storage or transportation. You can also customize the features to meet the specific power needs. A stationary generator would be less expensive but may cost more in the process of installation and maintenance.

Fuel Economy

Efficient fuel consumption during combustion helps not only economically but also environmentally. Fuel Economy=Electricity DeliveredAmount of Fuel Consumed

Noise Level

Generators are expected to be noisy by nature due to the rough machinery. However, having a generator that generated the least possible noise level is an advantage. Usually, propane generators are quieter than gasoline ones. A larger generator with a higher capacity could mean more loudness. Therefore, selecting the correct capacity of the generator is important. Learn more about are propane generators quieter?

Power Output Capacity

The power capacity you need basically determines the type of generator. Portable generators often come in the range of 0.25 to 4.5 kW while the stationary generators have a capacity of 1 to 10 kW. This capacity is the maximum amount of power that the generator can provide under normal operating conditions.

What Size Home Generator Do I Need?

The normal portable generators can help power up a few essential appliances including the refrigerator and the AC. But if you need to run all your household appliances without interruption during a blackout, you may need to go for a larger generator with more capacity. To power up most of your electrical appliances, you may need a generator producing 6000 to 7500 watts. So, if you need to have a portable generator, you will have to compromise on using certain electrical equipment. 

Since most power outages are fixed within a few hours, it wouldn’t have a major effect. However, if you live in a region where blackouts take up to a few days for restoration, you may need to think about going for a generator with a larger capacity. You can also choose between the two main types; Propane VS Gas Generators to suit your requirements.

Selecting The Ideal Generator Size

The power requirements vary from one home to another. Sizing the generator for your household requirements will make the selection process easier. To size a generator, identify the appliances that you need to power during the power outage. Then add up the wattages of each circuit on the breaker panel. Find the total power requirement in watts or kilowatts and make sure that the generator can produce the expected wattage. As mentioned previously, having a 48kW generator will handle all the circuits on the panel of your home. 

Important: There will be a spike in wattage when any appliance is started. This may be up to three times the running wattage of the appliance. If this overloads the generator, there will be interruptions due to affecting other circuits. 

What Happens If You Select An Undersize Generator?

Having an undersized generator will not affect most households where the maximum limit is not reached. This is because the full potential of the power usage will not be necessary most of the time. But if the load is oversized, then the breaker will trip disconnecting the load. You can recover it by removing the excess electrical circuits and bringing down the load to the generator’s rating. If the generator doesn’t have a breaker, then the engine will stall in the event of an overload. You can identify the generator going over its limits as the appliances may slow down or the lights may flicker. Overloading an undersized generator could even result in overheating and damaging the generator itself.

What Happens If You Select An Oversize Generator?

Oversizing a generator means having more power generated than required. Although you wouldn’t experience any tripping or stalling, there are other disadvantages to this. Larger generators cost more which is expenditure in vain for something you won’t need. For anyone looking for a 200 amp generator as a backup power source, the best option is to get the correctly sized generator based on the household power demand.

Frequently Asked Questions

What Size Portable Generator to Power 200 Amp Service?

What size generator for 100 amp service?

You may need a generator of 8 – 12 kW for a 100 amp service panel. Use a larger capacity if you have air conditioning. 

How many amps does a generator produce?

This depends on the capacity of the generator. On average, a 10 kW generator can produce about 42 amps regardless of whether portable or automatic. This amperage can be easily calculated by dividing the number of watts of your generator by the voltage.

How many watts in 200 amps?

You can find the number of watts by multiplying the amps by the respective voltage. Considering 240 V, Watts=240V×200A which gives 48,000 W.

How much does a 20000-watt generator cost?

The 20 kW generator is a very popular and budget-friendly model as most of them are air-cooled. The liquid-cooled cooled generators may comparatively cost more. These 20 kW generators usually cost around $5000, including a 200-Amp Automatic Transfer Switch (ATS).

How many watts are needed to run a whole house?

A typical home with average electrical appliances and essential items will need about 5000 – 7500 watts of power. This may slightly differ considering the household equipment in the residence.

How much does it cost to install a Generac 22kw generator?

For a 7 – 24 kW whole-house unit, a Generac generator would cost somewhere around $2,000 to $5,000 and a cost of installation of $3,000 to $5,000. The standby generators of this model turn on automatically during power outages. They run on liquid propane or natural gas.


Having a generator of 15 – 20 kW will be the most ideal 200 amp generator to power up an average home with electrical appliances. But if you need to power only a few selected appliances, you can go ahead with a generator of 6 – 7 kW. It is always better to estimate the correct power requirement and select the ideal size of generator to avoid any inconveniences. Don’t forget to schedule annual inspections of your generator by a professional technician to be on the safe side. This will ensure that the generator will function properly during a power outage. Considering the safety of generators, you will find it useful to know Are generators EMP proof?