What Size Generator Do I Need? [Generator Sizing Calculator]

What size generator do I need? To select a Generator from InverterGenerator.net that has enough power for your application, add the watts for items you may want to run at the same time. Use the total wattage, plus 20%, as your minimum power requirement.

Note: The wattage given below is an estimate. The actual wattage required for your appliances may differ from those listed. Check the nameplate on the appliance to determine the actual wattage required.

* Appliances and tools with induction motors (marked * in tables) may require from 3 to 7 times the listed wattage when starting. The start-up load of the appliance or tool determines whether a Generator has the capability to power it.

Be sure to check the specific wattage requirements and operating instructions for appliances/tools to be used. Also, air conditioners are a very difficult load because of the high start-up surge. Use the Locked Rotor Amps to determine the start-up surge requirement.

F.Y.I. ….. (conversion formula: Watts ÷ 120 volts = Amps …….. Amps x 120 volts = Watts)

For example, If you live in a home with a small furnace and city water, then a 3500-5500 watts generator will likely suffice to power your needs. On the other hand, if you have a larger furnace and/or a well pump, you should aim for a generator between 5500 to 6500 watts. We have some excellent guidelines to help you determine your wattage needs, use our generator calculator and find out what kind of generator you need.

Generator Calculator


Includes: Home back up power, Primary home power




Things You Need To Consider Before Determining The Ideal Size Of Generator You Need:


What Size Generator Do I Need

A standby generator is a device that provides backup power to a home or business in the event of a power outage. Standby generators are typically powered by natural gas or propane and can kick in automatically within seconds of a power outage. Many homeowners opt for a standby generator as a way to keep their families safe and comfortable during extended power outages.

It’s a very common question among consumers what size generator do I need? You should keep certain things in mind before finding the right generator size. First of all, the size of your inverter generator depends on the power outage you need.

Secondly, It depends on the purpose you want to use it for. If you want to power up your sensitive electronics and the whole house or you want to take it to the campsite. There are a lot of portable generators on the market that is large and heavy, which ruins their portability feature.

We will help you identify the right size portable generator you need, whether to run your house, home appliances, or you want to take it for a camp trip. Hope this article on “Big of a generator do I need” will help you buy the perfect match for you.

1. The Power Outage You Require

Starting with the power output. There are a lot of expensive portable generators with highly efficient features. Sometimes the power output of the generator depends on the size. As big as it is as it generates more power.

If you want to run sensitive electronics with the generator, the power outages will be different than the power requirement for the camp trip. Also, you need more power outages if you want to power your whole house.

You don’t expect the generator to contain the same amount of power output if you want to run the air conditioner or a refrigerator freezer that you need to power your small electronic appliances like phones, laptops, or a water heater.

So, you really don’t need to go for the best out of them all. All you have to do is figure out the exact same amount of power outages you need and buy a generator that fits the expected power output.

2. The Essential Safety Tools You Need With The Right Size Generator

The size of an inverter generator sometimes depends on the different tools it contains. The more equipment and tool it contains, the more heavy the generator is.

A whole house generator usually contains large and high-capacity equipment embedded in it, compared to a standby generator. Just because the home generators need to power up heavy devices like a refrigerator or an air conditioner.

Standby generators are basically used to power smaller home appliances. Such as lights. On the other hand, the whole house generators are much used to run the power electric devices for several hours.

Moreover, You may not need all the tools. So just be accurate about what you need and get yourself the ideal match with a proper size.

3. The Purpose You Are Using It For

A lot of people use portable generators for a lot of purposes. One of the most important factors you must consider is matching your power needs with the generator’s power supply.

Some people just need a small portable generator for camping. They don’t require much power capacity, they focus on portability. Most of the generators are manufactured based on their functionality and the power watts they produce.

The other people want to power up the whole house as an emergency power backup, an alternative to regular electricity. The inverter generators generate a huge amount of energy to run a whole house, including the home appliances like a refrigerator or a microwave.

Some people just need to run their small devices. And the rest of them wants to use it for other purposes. It is an obvious fact that as much power the generator produces, as heavy it will be. So buy your generator based on the exact range of power wattage you need.

4. The Features And Functionalities You Demand

Some people demand extra features like extra running wattage, remote start, or a transfer switch feature. These features require an extra tool that makes the generators more heavy than usual.

Also, the size of the generators depends on some functionalities like fuel consumption and power production ( running wattage and starting wattage).

If you want to run heavy electric equipment, you should not expect your machine to have low running and starting wattage. Both of them are important to run a large and heavy electric device.

A portable generator basically designed to generate power from a battery source to run all types of home appliances. They are also made with modern soundproof technology to reduce the high-level sound.

5. The Generator That Fits Your Budget

You don’t always have to go for the best to ensure the best service. The generators are made in various categories. Each generator is suitable for the particular work it is made for.

So, fix your budget and find the ideal match for you. There is no need to get a highly efficient portable generator by spending a lot of money if you want to take it to camp.

However, sometimes a big-sized generator costs some extra dollars. So, you don’t have to buy the big ones if you don’t need them.

How To Calculate What Size Generator You Need?

Now we come to the point where we will describe the procedure to find out how to calculate what size generator you need.

Step 1: Find out your necessary amount of wattage

The most important factor that we consider before buying a generator is the power watts we need. Make a list of the appliances you use regularly and estimate daily power watts.

Then get yourself an ideal match. You might want to use it on a camp trip, for your RV, or for running the whole house, including AC or lights. Every time you will need various power watts.

Step 2: Use the calculator above to calculate the necessary power outage for every appliance

There is various power outputs produced by the generators. You must know how many watts you are going to need based on your necessary tools. We have provided a calculator that will calculate the power watts required for various appliances. Just before you get yourself one right size generator, you must find out the estimated watt used by your appliances.

Step 3: Buy a little bit large generator than your needs

It’s better to have a generator that provides you with some extra watts in case you need it. The small generators are basically made for camp purposes and cannot provide extra energy in case someone needs it badly. The larger generators can hold more fuel.

So, they can provide a full power supply in half the fuel load of the central air unit. Running a half-load generator gives you a low noise level output that ensures a clean environment free from sound pollution.

Ideal Generator Size For Running Sensitive Electronics:

Volt AC power
A label found in a Water Heater. This one consumes 4500 watts, operating at 240 VAC (Volt AC power).

There is an easy mention to know what size generator you need for running sensitive electronics. It’s pretty difficult to choose the right one according to your necessity.

First of all, you don’t require a huge power outage to run a small appliance. You must know the ideal generator for running sensitive electronics is the one that runs in a total harmonic distortion (THD) which generates a pure sine wave.

It is essential if you want a safe running session and if you don’t want your delicate device to face any damage.

As you don’t need a generator with huge running watts and starting watts, the generator size should be moderate, similar to a portable generator that is usually taken to the tailgating.

Ideal Generator Size For Running The Whole House:

Need a generator for your home? The suggestion is much nonsimilar to the previous one. The wattage requirements you need to run the whole house are quite different than the other purposes.

Most of the generators that are made for running a home are a little bit large in size, while the camping generators are smaller. House generators are a great source of electricity when you are very much in need of an emergency power outage.

In this case, you will need a generator that can run every single necessary piece of equipment, tools, and other important home appliances. Also, the generator needs to run in a total harmonic distortion to provide safety to a sensitive electronic device and a kitchen tool.

The total harmonic distortion feature generates a pure sine wave curve that is very important to run delicate devices. Also, you need to run big appliances like air conditioners or refrigerators, which require more power wattage.

An ideal generator that matches all these important requirements carries much more weight than the average inverter generator. It’s on you which one you want to choose based on your ideal preferences.

Ideal Generator Size For Camping:

Most of the time, the generators that are preferred for camping are lightweight portable generators that weigh not more than 50 pounds with excellent starting watts and running watts. Because the purpose requires portability as you need a generator that can be moved around easily.

The camping generators usually come up in a small design and have great functionalities. The fuel consumption, transfer switch, remote start, and other features will make you consider these portable generators as the best choice with the excellent power wattage and small size.

There are some models with much larger sizes, even though we can keep these on our list as they are far smaller than the inverter generators.

Coming to the power watts they generate. It is obvious that these camp generators cannot produce a huge amount of energy to run big devices that are used at home, but the power wattage is enough to run all the necessary works that you might need on a camp trip.

Why Do Getting The Right Size Generator Matter?

Generators are the best energy source for emergency power supply which are able to run your household appliances and RV devices for several hours or help you experience a great camp trip by producing power using natural gas or propane as fuel. The inverter generators generate power by using batteries instead of fuel.

The size of the generators varies from brand to brand, model to model. Also, the size depends on the functionalities and features. Some generators that produce a huge power wattage contain a larger size. Some have a large design to maintain good running and starting wattage. Some generators are bigger to contain extra features and functionalities.

Most of the generators are sized based on their using purposes. It is very important to match the generator size with the purposes. That will give you the following benefits:

1. You’ll Get A Longer Lifespan

One of the best importance of matching the generator size with the purpose is you will get a longer lifespan compared to the most used standby generators. The right size generator will provide you with the right amount of power wattage containing the proper running watts and starting watts.

That will limit the usability of the generator, and you will only be able to run some particular tools with it. That will decrease the extra pressure that your generator would have if you used it in another category of tools. This will ultimately increase the lifespan of your generator and help you save money.

2. The Right Size Generator Will Provide You Safety

One of the most common questions among the customers is what size generator do I need if I want to pursue extra safety for my devices. The generators that are must necessary for running the sensitive electronics are the ones that produce a pure sine wave.

The feature provides extra safety to sensitive electronics. If you don’t intend to get this feature, you will have a generator that is mismatched to your purpose.

3. Easy Portability

One of the most important advantages of buying the right size generator is that you can carry the generator easily to any place. Especially the camp generators are so portable and small in size that they will help you keep the ability to move them around.

Don’t worry about the large ones. Most of the large generators are not very heavy to make you fall into an unexpected situation so that you can’t carry them. They weigh not more than 100 pounds. Keep them on your buying list.