What Size Backup Generator Do I Need?

The size of the backup generator you’ll need will depend on a few different factors, including the amount of power you’ll need to keep your home up and running and the type of fuel you’ll be using. Here’s a quick rundown of what you’ll need to consider when choosing a backup generator for your home.

How Many Watts Do I Need For a Home Backup Generator?

In order to power a home, what size generator do I need?

Running the most basic home appliances, such as the lights, a freezer and the pump for a well, will require a generator that is rated between 5,000 and 7,500 watts.

The size of the backup generator needed in watts depends on the size of the house and how many appliances you’ll be running simultaneously.

A typical small 2-bedroom house can usually be powered simultaneously with a 7,500-watt generator.

A larger 3-4 bedroom house will need at least an 18-22 kilowatt home backup generator.

Add a safety buffer of 20% in kilowatts to provide for future power requirements. If your generator’s minimum capacity is 17.5 kilowatts based on your estimated peak electricity consumption, for example, then you should buy a 21 kilowatt generator to run your house.

Keep in mind that you need to size your backup generator for the highest demand season. That should be the dead of Winter (high heater use) in northern climes and dead of Summer (high AC use) in desert and southern climes. In milder seasons you will not use the whole capacity, but it’s essential you have adequate backup power for the most dangerous situations of the year.

How Do I Calculate What Size Generator I Need?

First, you nee to estimate your peak electricity demand. Total Amps drawn x Supply Voltage / 1,000 equals kW at full load.

Then you need to determine the kilowatts capacity of the generator you need to comfortably power your home or business along with a buffer. A backup generator‘s capacity is calculated as follows: kW at full load divided by 0.25. Generator size = kW at full load + 20% additional kW in reserve to achieve 120% peak estimated power.

Retail use: 50 kW + 10 watts per square foot for retail use.

Commercial use: 50 kW + 5 watts per square foot.

Highly rated backup generators to check out:

Generac Guardian 24kW Home Standby Generator with Transfer Switch (Wi-Fi Enabled)

DuroMax XP12000EH Backup Generator 12kW for Home or RV – Gas or Propane Dual Fuel

Westinghouse 12.5kW Dual Fuel Home Backup Portable Generator

As an Amazon Associate, SelectSafety earns commissions from qualifying purchases made through links in this post.

How Big a Generator Do I Need for a 2500 Square Foot House?

For a 2500-square-foot house with gas heat and hot water, a 20kW generator should be sufficient. It’s much better if the cooktop is gas-powered as well. A 20-kilowatt sized home backup generator can power a central air conditioner, as well as the majority of a home’s outlets and lights.

How Big a Generator Do I Need for a 3000 Square Foot House?

Two central air conditioners, an electric stove, and a Jacuzzi tub can consume 25kW to 30kW in a 3,000-square-foot residence. Newer options include a “load-management system,” which generator feature that can power your home’s systems selectively, rather than all at once.

Related Questions and Answers

How big of a house will a 22kw generator run?

It can power a 3,000-4,000 square foot home with a 22-kilowatt generator. At the same time, it may operate the heating and air-conditioning systems. Avoid wasting gas by limiting the number of appliances that are used while the generator is running.

How much is a generator for a 2000 sq ft house?

The national average for a whole-house generator is $10,000 to $20,000.

An 18kW generator capable of powering a 2,000-square-foot house with heating, cooling, hot water and lights costs around $15,000 on average, according to the National Renewable Energy Laboratory.

What size generator do I need to run a 5-hp motor?

Generally speaking, you should always get a generator 1.5 times larger than the motor, thus for a 5 HP pump you should have 7.5 kva.

How big of a backup generator do I need?

Choosing which size backup generator you need is not difficult if you know what to include. This video should help:

How many amps does a whole house generator use?

Equipment, appliances, pumps, air conditioners, and other electrical devices need a certain generator size. If you have a 200-amp service panel, you’ll need around 140 to 160 amps of 240 volts of electricity to run all of your appliances at the same time.

How many watts is a whole house generator?

Generating power for a whole house is possible starting at 12,000 watts and going up from there. Lighting, fan, TV, a refrigerator, a computer, and space heaters are just some of the appliances that may be powered by an outlet.

Will a 14kw generator run my house?

Fourteen to twenty kilowatts per room is recommended. All of your home’s essentials, as well as some you’d want to have electricity in to make it more pleasant during a power outage can also be included.

How many watts does a 3000-square foot house use?

In 2015, a 3,000-square-foot house used an average of 14,210 kWh, while a 2,000-square-foot home used 12,271 kWh. Think about why your power consumption is greater or lower when comparing your use to the averages.

How do you hook a generator to a house?

To use your generator, just connect the gen wire to a 20- or 30-amp outlet. Extension cables may be securely connected inside using the outlet on the other end, which has numerous home outlets separated into it.

Will a 30kw generator run my house?

A 20kw generator is too tiny for a normal home, which requires between 25 and 40 kilowatts of power. It takes around 30 to 50 kilowatts of electricity to run the fundamental electrical functions of a typical American house. If the grid goes down, you’ll need at least a 30 kW generator to keep your house powered up.

What size generator do I need for a 2hp compressor?

Starting wattage for a 2 HP Air Compressor is 7770 watts, whereas the operating wattage is just 2800.


The size of the backup generator you need for your home depends on the dimensions of your home and its overall energy requirements. Make sure to do your due diligence and calculate the amount of energy you will require when the grid goes down.

Choosing “what size generator is needed for a 2,500 square foot house” is fairly straightforward if you know what to consider. The answer to the query depends on how much power you want your generator to produce and what type of fuel you are using.

NEXT UP: How To Determine The Power Of A Backup Generator

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Leon Ashcraft
About Leon Ashcraft

Leon Ashcraft is a Safety Instructor and consultant in Colorado with focus on OSHA, environmental health and safety, transportation safety, oil & gas, rescue operations and construction safety. Learn more about Leon here or connect with him on Twitter | LinkedIn | Medium