Calculate Watts Needed For Your Whole House, Camper, AC, or RV Generator Size

Last Updated on October 2, 2023 by kiezelamquiz

This calculator will help you estimate what size generator you need for your house, RV, camper, or AC unit so you know what kind of generator to purchase.

The numbers I used are averages, they may vary depending on your equipment.

To calculate what size generator wattage you need, change the “How many?” field

When shopping for a generator, one of the most important factors is going to be the wattage capacity. After all, you are buying a generator to handle a certain amount of appliances or electronics plugged into it. To ensure that you are getting the right size generator for your specific application, you will need to calculate the wattage you will need.

Today, we are going to break down how many watts you will need for different scenarios, as well as educate you on a few things you will need to know when purchasing a generator.

How Do I Calculate My Wattage Needs?

Calculating the wattage needs of your generator is easy with our generator wattage calculator. Simply make a list of all of the appliances you plan on using with your generator to start adding up the wattage demands.

You can find out how many watts each appliance will use by looking for a manufacturer decal on the appliance, or by contacting the manufacturer. Once you have these wattages, you can add them into our calculator to find out exactly how many starting watts and surge watts you will need.

It is always a good idea to find a generator that has more wattage than you need. This allows you to not use your generator at full capacity which can increase wear and tear, but it also allows for increased usage from older appliances. As appliances grow older, they become less efficient, meaning they are going to start using more watts. A refrigerator that may have once used 800 watts could possibly be using 900-1000 watts, depending on it’s condition.

How Many Watts Do I Need For Home Back Up Power?

One of the most popular uses for a portable generator is home back up power, but how do you know which size generator you need for a whole house? In the event of a power outage from a storm or blackout, one of your only options for powering up your home appliances is a generator. Since each home is different, finding a generator that can power your needed appliances may vary, but we can give you a general idea of what to look for.

If you have gone through power outages before from a severe storm, you may know how long it takes to normally restore power. For those who are prone to more devastating storms such as a hurricane or tornado, your needs may differ as you will need a longer lasting generator or maybe even a dual fuel if gasoline gets hard to find.

The first thing that you are going to want to do is to figure out which appliances you are going to want to power during a blackout. This is usually going to include a radio or TV, a small refrigerator, and a microwave to get you through a few hours or even one day. If you think you are going to need to power up a furnace, you are going to need to look into a higher wattage furnace generator.

Once you have all of those appliances listed out, figure out how many watts they use and plug them into our calculator. For most applications a generator with 2,000-5,000 watts should be sufficient enough to get you through a couple of days of power loss.

How Many Watts Do I Need For A Job Site?

Another common use for a portable generator is using them on a job site. Many job sites can go for months without electricity being set up. This requires the use of a portable generator to get power to tools, lights, and other electronics you may need. The best part of using a generator on a job site is that the noise level is usually not a deciding factor.

However, there are two huge factors you want to take into consideration when purchasing a portable generator for your job site: wattage rating and build quality.

Looking at power ratings first, you are going to want to take into consideration the type of tools or lights that will be used with your generator. For light duty tools such as drills, saws, and small lights, a 2,000-3,000 watt generator should be more than enough. If you plan on using multiple tools at once or some heavier duty tools, a 3,000-6,000 watt generator may be more useful.

As far as build quality goes, there are going to be certain features you will want if you are going to be using your generator outdoors on a job site. With generators having multiple outlets integrated onto the side of the generator, you will want to find one that has plastic outlet covers. These covers act as a seal for the outlet which protect them from dirt, debris, and moisture. You may also want to take a look at the wheels as well. Rubber, inflatable wheels will be easier to maneuver over harsher terrains when compared to solid plastic wheels. Lastly, finding a generator with a rugged roll cage will keep it protected from falling debris.

How Many Watts Do I Need For Recreational Use?

Using a portable generator for recreational use can fall under many different categories. They can be used for camping, RV power, tailgating and more. To help give you a better idea of what you may need, let’s look at each of these a little closer.

For camping, not in an RV, you may need a generator that is going to power a griddle, radio, TV, or any other electronic that you may want to take with you. For this type of use, you can usually get by with a 1,000-2,000 watt generator. You will want to look for one that is quiet and has USB outlets to charge up cell phones, cameras, and other small electronics you have brought with you.

If you choose to go camping with an RV, you are going to most likely need a larger generator. An RV is going to need enough power for running appliances, AC or heating, lights, and other items built into the RV. For this setup, I would suggest anywhere from 2,000-8,000 watts depending on the size of the RV.

Lastly, tailgating with a generator may be something some have never thought of, but if you plan on powering a TV or radio for pregame shows, you are going to need a generator. Now the size of the generator that you will need will ultimately depend on how much you plan on powering up but for the most part, a 2,500 watt generator should be more than enough.

Using A Parallel Capable Generator

If you are unsure if you need a larger generator at this time, you can look for a generator that has parallel capabilities. A generator that is parallel capable means that you can hook up another generator of the same model for twice the power. In some instances, a parallel cable is sold that has larger outlets that can be powered with both generators such as a 30 or 50 amp outlet.

This allows you to purchase say a 2,200 watt generator for now and when you are needing more power, you can purchase another similar generator that can hook up in parallel for 4,400 watts. This is also great for those who would rather have two smaller generators to use in different places but have the ability to use them together to power something larger.

Not all generators are parallel capable, so it is important to look for this feature if you plan on going this route. You will also want to double check to see if the generator comes with the parallel cable or if you have to purchase it separately.

Dual Fuel Capabilities

Another great feature when it comes to portable generators is dual fuel, or hybrid generators. These generators are able to run off of gasoline or propane as their source of fuel. This allows you to have the versatility to use either or if you run out of your primary fuel source.

For example, if you are using gasoline and your run time is 8 hours, you can switch over to propane when you run out. This will allow for longer run times between refueling and is a great way to be versatile during a natural disaster when gasoline may be hard to find.

It is important to take note of the different run times and wattage capabilities when using each power source. Propane does have a longer run time when using a 40 lb bottle, but the wattage capacities are going to be lower.

All in all, a hybrid generator is going to give you great benefits, especially for those who are looking at running their generators for an extended period of time.

Starting Watts Vs Running Watts

When purchasing a generator, it is also important to know the difference between starting watts and running watts. Oftentimes, these are confused, causing people to overload and damage their generators. The last thing you want to do is spend a lot of money on a new generator only to have it not be able to power up the things you need. Let’s take a look at the two and dive into the differences.

Starting Watts

Starting watts are exactly what they are named to be, the watts needed for the 2-3 seconds of extra wattage needs from motor driven appliances. This is going to be for items such as refrigerators, large tools, and other big appliances. This is going to be the higher number on the generator’s wattage ratings due to more wattage needs when an appliance starts up.

Many appliances are going to have this rating on their wattage decal, but for others, you may need to call the manufacturer to find out the exact wattage number. You will not want to guess if you don’t have to as you can easily overload your generator if you are not careful.

Running Watts

Running watts are going to be pretty self explanatory as well. It is going to be the maximum number of watts that your generator can provide when your appliances are running. This will of course be after the first couple of seconds peak watts (starting watts).

This is going to be the most common rating that most appliances will have listed on the appliance as it is the most important. When appliances advertise their wattage rating, you can guarantee that they will be referring to the running watts.

What Are Other Factors That May Affect Wattage Demands?

Although you may have gotten everything figured out and planned out, there are a few things you may want to take into consideration that could affect wattage demands.

Age Of Appliances

As appliances get older, they become less efficient. Whether it’s electronic breakdown, unmaintained wear items, or simply getting old, appliances can start to use more energy over the years. This needs to be taken into consideration when purchasing a generator for specific larger appliances.

Heavier Than Expected Loads

While this shouldn’t be too big of a problem, for items such as a/c systems and furnaces, they may need to use more power in extreme weather conditions. Most appliances these days will not have that problem, but it is something you may want to look at.

Improper Extension Cord Usage

Last but not least, using the wrong type of extension cord can cause damage to your generator. Be sure to check with your generator manufacturer to ensure you are using the recommended extension cord to prevent overload or damage.


I hope that this generator wattage calculator guide has helped you get a better understanding of what size generator you may need. It is important to remember that you need to take the time to research each appliance and tool that you will be using on your generator to ensure that they are all calculated to prevent overloading your generator.

Now that you have got all of your watts calculated, you should feel confident enough to make a smart purchasing decision. Get out there and enjoy your new generator! is an independent review business. I am not affiliated with any manufacturers and do not accept paid reviews. When you buy through my links, I may earn a commission which helps me purchase more generators for testing. - Scott Krager


  1. So, if I have video and film production lights that go from 250-300 watts to 4k watts, and 120v to 240v how do I calculate what size generator I need? For example, I am looking at 10k and 12k hybrid generators (gas or propane), like these: DuroMax XP10000E 10000 Watt 16 HP Generator DuroMax XP12000E 12000 Watt for aroung $1,000.00. Say, I am going to light a set using three 4k lights which equals 12,000 watts is that one generator going to run those lights. Correct? Please advise. Thank you, Duker…

    1. Hi Duker, That won’t be enough, you have to look at Running watts, not starting or surge watts. If you really need to power 12K watts of lamps, you should look at 15,000 Running watts generators, like the duromax XP15000EH, or generac’s GP15000E. Also consider the advertised run-time at half load to give you an idea of just how much time you will be able to run your setup. Hybrid /dual-fuel generators will give you more flexibility.

    1. Hi Thomas, yes you can find a number of “Tri-fuel kits” online, these are made for specific brands and models of generators. On most units you do not need to do any modifications but they are best installed by a professional.

  2. I live in the hill there is no electricity..what would i need to have a small regular tv and lights. In the house maybe a small appliance going.

  3. I have a well I need to supply power to incase of power outage, either caused by storm outages, or PG&E shutting off the grid for “safety”.
    your calculator indicated that my need would be to supply 5800W of power.

  4. Hi –
    I’m in the same boat as Robert, trying to get a generator in case PG and E turns off power
    My fridge is 115 V/10 amps so I know running watts is 1150 …I am not sure how to find startup watts. Since my device running watts are so much higher than average, I dont want to use number (2000W) that I see quoted online for average start up watts
    Can you help?

  5. Hi. I have a converted a container into a cafe and require a generator to run it from as there is no power supply. Any advice on whether a 15kva generator will be enough to run everything and something which lasts for 15hrs per day

  6. If I hook up 12 – 12V – 6amp LED transformers what size, rechargeable, generator would I need to run it for 8 hrs.?

  7. I have a 2500 SF home all electric heat and the usual appliances. What size standby generator do you suggest.

  8. I have a 50″ 4k tv and a portable trek antenna’ I wanna tailgate for about 8 hrs, what size generator what i need?


  9. I have a well pump, electric hot water heater, a washer electric dryer, microwave oven, 2 televisions, LED house lighting, a dishwasher, and an auxiliary pump to bring water from the river to a large storage tank, and a hot tub.

    I realize all of these items are unlikely to be running at the same time. I get it that in an emergency, I may choose to leave the breakers off for some of my circuits so I can choose what will get power. I’m thinking of getting a 7,000 – 9000 watts dual fuel generator which will be run on propane. Please advise. Thanks

  10. Have a 12,000 peak watt generator, running watts is 9500, i have a 580 sq ft house with central air, will this genny run it and everything else?

  11. I have a 3 ton 28000 btu central A/C. What is minimum wattage I need in a portable generator? Thank You

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