How Big Of a Generator Do I Need For My House

How Big Of a Generator do I Need For My House will guide you through choosing a generator that fits well in your need by following just some simple steps.

One of the most difficult purchasing decisions is choosing a generator that can be able to generate power for all your needs.

If a generator cannot meet all your specific requirements then it is no good, whether it is a standby or a prime generator.

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This is because it can put the units and devices that are connected in it under stress or even damage them.

Determining the exact size of the generator you need involves several factors and considerations

Choosing between single phase, 3 phase, kilowatt, welder, motor starting or standby generators can be a daunting task.

This article is compiled to help you avoid such confusion and help you have a better idea of how the process of generator sizing works.

Before buying anything electrical, it is advisable that you talk to a certified electrician.

Choosing the generator of the right size

generator size

According to the Energy Information Administration of the US, a typical household of America loses electrical power two times every year for about 3 hours.

Sometimes the power can go off for a few days or even weeks.

This depends on the cause of power loss like extreme weather or natural disasters.

When these outages occur, homeowners face a lot of inconveniences and may also incur some expenses such as spoilt food, pipes freezing and basements that are flooded.

The first line of defense for these problems is a generator.

The generators range from small recreational units that go for a few hundred dollars, to big standby generators that can power the whole house and can cost up to $5,000.

Dave Trezza who is a consumer reports engineer advises to buy a small generator that will be able to meet your power needs and that will consume the minimum amount of fuel.

Different scenarios of a power outage and the size of the generator you can choose.

1. Power Outages Occur Frequently

The first scenario is when the power goes off frequently. Sometimes the outages are prolonged, making the matter worse.

This scenario may also apply if you live near an area where there are extreme weather conditions such as hurricanes, ice storms, and blizzards.

Here is a list of generators you can consider for these scenarios

  • Home standby generator
  • Large inverter generator
  • Portable generator
How Big Of a Generator Do I Need For My House

All of these three types of generators have enough power for your entire home.

Moreover, they can also be connected directly to your circuit breaker panel.

This will allow you to power the devices that are connected to a circuit directly such as air conditioning, central heating system, pumps, and water heaters.

If any of these devices are available in your home, it is important that you have a backup generator.

Also, make sure that in your circuit breaker box a transfer switch is installed. A certified electrician should be able to get that job done.

2. There are outages occasionally.

On some occasions, the power losses last longer than expected, and you don’t want to incur a lot of expenses on standby home generators.

List of generators you can consider for these scenarios

  • Portable generator
  • Large inverter generator

If the power outages are not many per year, and you don’t want to spend up to $10000 for a stationary standby generator to be installed, then you can go for a portable or large inverter generator.

For these generators, you will have to store them in your garage and pull them out only in case of a power outage. These generators also need a transfer switch installed.

3. The power outage occurs rarely

In this scenario, you can have the generator just for a piece of mind.

List of generators you can consider for these scenarios

  • Middle size inverter generator.
  • Recreational inverter

The middle size inverter generator can power a fridge and space heater or a window air conditioner.

Because of their small size, the recreational generators can fit in the back of a pick-up truck and can produce enough power to run a cooktop and a TV.

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Choosing a Generator Based on the Wattage

How Big Of a Generator

Another quick and efficient way of determining the size of the generator you need during a power outage is to find the total wattage of every appliance you want to power during the outage.

Before you start doing your calculations, you need to remember that some of the appliances such as the refrigerators, the air conditioners, and the pumps create power surges momentarily when they are running.

If you do not account for these surges, they can throw your calculations off. You also need to note the total wattage of all the appliances that are hard-wired in your home circuit.

Recreational Inverter Generator

This generator can produce up to 2000 watts.

The cost varies from $400 to $1000 depending on the model.


This generator is the lightest.

It is the quietest model.

There is no installation cost.

Since they are small, they are easy to store and move around.

You can use them in pairs to increase the power output.

Most of them come with features that are user-friendly such as apps for smartphones and fuel indicators.


It can only power a refrigerator, some light bulbs, and a phone charger.

They can’t be connected directly to the main circuit. They can only be used with a standard plug.

The models that are the most expensive cost almost the same as portable generators which can do more.

Middle Size Inverter Generator

This type of generator can produce up to 3500 watts.

The cost ranges from $1000 to $1700.


It is light in weight because most models weigh less than 150 pounds.

Very efficient. It can run the lights and a fridge for up to 18 hours with 2 gallons of gas.

It does not make a lot of noise.


It can power items that require up to 110 volts with a standard plug.

Cooling and heating appliances cannot be powered by this type of generator.

Installation costs for the 110-volt transfer switch make it an impractical choice because you can acquire a portable generator with a 220-volt transfer switch for the same amount of money.

Portable Generator

It can produce up to 7500 watts.

The cost ranges from $700 to $2800.


The portable generator has the best value in terms of cost versus the capacity it produces. There are models that can produce enough power to meet all your home power needs.

It can be connected directly to your circuit panel to provide power to the hard-wired appliances such as the pumps.


The cost for connecting to the circuit panel to power the pumps is almost equivalent to the generator cost itself.

They are louder than standby home generators and large inverter generators.

The use more fuel than large inverters and run on gasoline only.

They are heavy since most of them weigh more than 300 pounds.

They should not be used when snowing or raining without protection.

Large Inverter Generator

It can produce up to 7500 watts.

The cost ranges from $1400 to $4000.


The energy produced by most of these generators can run a fridge, some lights and other essential appliances such as an air conditioning unit or a small furnace.

They can be connected to your circuit panel to run hard-wired devices.

The power produced by these generators is steady and can, therefore, run sensitive devices such as stereo sets.

Their fuel consumption is efficient.


These types of generators are expensive. Models with costs varying from $3000 to $4000 are the only ones which qualify for serious warranty considerations.

Propane or natural gas or natural gas can be used as fuel.

Home Standby Generator

generator Do I Need For My House

This is the biggest type of generator that can be considered for powering a home during a power outage.

It can produce up to 20,000 watts of power.

The cost of this generator varies from $2000 to $6000.


These generators are installed permanently, usually in the basement or next to the house.

When the power goes off, they start automatically. This ensures uninterrupted power supply to the house.

They can provide power to everything in the house at once, up to their maximum power output.

Propane or natural gas can be used as fuel for these generators.

There is no need for connecting cables or even starting the engine.


The relatively cost more than the other generators.

Also, they have high installation costs which are not included in the pricing.

They can’t be placed in areas where there is likely to be flooded in the event of a flood.

large generator for house

Generator Power Calculator

To get the amount of power that you need to get out of your generator, you first need to establish the required peak (starting) and continuous (running) watts for every appliance in your house. Free generator wattage calculator online.

If you get the wrong starting or running watts, then your generator will not be able to power your appliance.

General Household Appliances and the Wattage they Require

Running load


Description Running kW Amps at 120 V Amps at 240 V

Electric heat per 1000 ft2 12 N/A 50

Heat pump elements per 1000 ft2 7 N/A 29

Dryer 5.5 N/A 23

Hot tub 10 N/A 50

Range oven/stove topper burner 8 N/A 30

Hot water 4.5 N/A 19

General lighting and receptacles per 1000 ft2 3 24.9 N/A

Blow dryer 1.25 10.4 N/A

Dishwasher 1.5 12.5 N/A

Microwave 1 8.3 N/A

Toasters 1 8.3 N/A

Home entertainment center 1 8.3 N/A

Computer 1 8.3 N/A

Kitchen 1.5 12.5 N/A

Laundry 1.5 12.5 N/A

Determine How Many Appliances will be Running at the Same Time

How Big Of a Generator For My House

Furthermore,  you can use the information above to choose the correct size of a generator if you plan to run only one appliance from your generator.

But you need to take a different approach in case you need to run more than one appliance from your generator.

You take the sum of all the wattages, starting with the highest wattage. This gives you the total number of watts you need from a generator.

If you purchase a generator that cannot produce the required amount of power, this will trigger the overload circuit breaker, and this will stop the generator from producing power.

Therefore, you need to be very careful when choosing the right generator according to your power needs.

You need a generator that can power up all your appliances without any problems.

Generator Wattage Chart

Appliance Rated Watts Surge Watts

Survival Appliances

Light bulbs 75 each 75 each

Refrigerator/Freezer 500 2000

Sump Pump 800 2000

Water Pump (1/3 HP) 1000 3000


Furnace Fan (1/2 HP)* 875 2300

Electric Blanket 400 400

Space Heater 1800 1800

Heat Pump* 4700 12000


Dehumidifier 650 800

Attic Fan* 300 900

Table Fan 800 2000

Window Air Conditioner 1200 4800

Central Air (10k BTU)* 1500 6000

Also, Central Air (24k BTU)* 3800 15000

Central Air (40k BTU)* 6000 24000

Family Room

Computer 300 300

CD Player 100 100

VCR 100 100

Radio 100 100

Television 300 300

Receiver 420 420


Microwave 800 800

Blender 300 900

Coffee Maker 1500 1500

Electric Range (1 element) 1500 1500

Toaster (2-slice) 1000 1600

Dishwasher (Hot Dry) 1500 3000

Electric Oven 3410 3410

Laundry Room

Iron 1200 1200

Washing Machine 1150 3400

Gas Clothes Dryer 700 2500

Electric Clothes Dryer 5400 6750

Other Important Items

Security System* 500 500

Deep Freezer 500 1000

Hair Dryer 1200 1200

Garage Door Opener (1/3 HP) 750 750

Electric Water Heater* 4000 4000

What can various types of generators be able to power?

18000 watts generator

A generator that produces up to 18000 watts of power can be able to run the following appliances:

  • Tools with up to 1000 watts rated
  • Toaster
  • Portable drill
  • Jigsaw
  • General lighting
  • Heating
  • TV
  • Small refrigerator

This is the most ideal generator for general home usage. It is not heavy and can power home appliances without any problems.

3500 watts generator

This type of generator can power appliances with a rate of up to 2200 watts. These include;

  • Radial saw or a small a/c.
  • General home lighting
  • Heating
  • TV
  • Microwave oven
  • Small pumps and motors, depending on the model.
  • 4.4 kVa is the best option.

6000 watts Generator

This type of generator can power appliances with the rate of 3400 watts. These may include:

  • Radial saw or small air conditioner
  • General home lighting
  • TV
  • Microwave oven
  • And pumps.
  • 1 horsepower motor (depending on the model)

For the best results, take 7 kV

It is essential that when choosing a generator, you choose a generator that fits your needs appropriately.

big generator for house

If for instance, you buy a generator that is too small, it will not allow you to run some of your appliances during a power loss.

In fact, overloading your generator may result to your generator breaking down or some of your appliances damaged.

If you choose a generator that is too big on the other hand, you will end up spending more on the buying cost, installation, and fuel and maintenance costs.

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The correct size of a generator that you need depends on the number of appliances that you wish to keep running during a power shortage.

Moreover,  you also need to keep in mind that some appliances require higher start-up voltage (surge) and therefore you need to account for them.

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