What Size Generator Do I Need?

Ok, so you’re looking to purchase a generator for your home or camping trip but you are just not sure exactly what size you need. I understand completely. Even just doing a simple search on we can find hundred of matches all that seem to be at a different size. Should you get a two-thousand watt system or a ten-thousand watt? Where do you even begin? Well, in this article we’re going to take the time to go through exactly how to size your generator for your needs. Without further ague, let’s dig in!

The most important factor that you need to consider when purchasing a generator is what size of unit that you need. A generator’s power is measured in watts. The higher the watts the more power your unit will have. These portable generators can be as low as five-hundred watts or as high as forty-thousand watts. It all depends on what you need your generator for. Whatever your case is for getting a generator you should always take the time and care to acquire the right sized unit for your needs.

Now, the best way to determine the right wattage requirements is to simply add the watts of each appliance/product that you want to use during your power outage and then add them all up for your total amount. (This guide from Amazon helps give you watt estimates on certain appliances.) Most small and regular sized appliances will have stickers or labels on them telling you exactly how many watts they take. If you notice that your appliance doesn’t have a wattage rating on it but instead has a volts and amperage don’t worry. We can still find the amount of watts that are needed. All you have to do is take the number of volts times the number of amperage. As an example, let’s say you have an appliance that takes one-hundred and ten volts and and five amps. Let’s do the math:

110 volts * 5 amps = 550 watts.

If you go this route, please be aware that some products have a cycle on process when being turned on. During this cycle on they may need additional wattage and then cycle back down to their normal watt usage. There are whats called starting watts and running watts. Starting watts, also known as surge watts, are how much power it will take to turn your system on whereas a running watt is how much continuous power it will take to maintain your system rather it be an air conditioner, oven, or whatever. Just like before when looking at watts of your appliance you can find starting and running watts either on a label on your appliance, on the instruction manual, or online at the manufacturer’s website. Some example appliances that have different starting and running watts are your refrigerators, freezers, air conditioners, and well pumps.

Wen 56200i Portable Generator
Wen 56200i Portable Generator

If you run the mistake of not accounting for starting watts and just add up your running watts you can easily short out your generator and damage your system. If you are lucky your generator has a automatic shut-off switch to prevent damage. Even though this starting cycle process only takes a few seconds you will still need that extra power to get the unit running. If you find that you cannot find the exact starting watts on your system, you can usually make an estimate by taking two to three times the running watts number.

Along with calculating all of the watts that are required it is also recommended to take that number of watts and add an additional ten or twenty percent. This increase in watts gives you some leeway when using your generator and also allows for a margin of error if you ended up missing something or pulled the wrong wattage on a unit.

To make things simpler we’re going to give a quick estimate of watts and what can be used. Please note that this is an estimate and it is best to add your wattage like we mentioned above.

  • 2,000-3,000 Watts – This is enough for a refrigerator, a computer or two, some lights, and a few phone chargers. This is also what most people use when going on camping trips and for their campers or RVs. Please note that while this size works for most campers and RVs, if you plan to power your air conditioner as well then you will need to go quite a bit higher in watts to ensure you have the proper capacity.
  • 4,000-5,000 Watts – Along with what we mentioned above you can also add a clothes washer and dryer.
  • 6,000-8,000 Watts – Along with what we mentioned above you would have enough power to turn on your furnace.
  • 9,000 Watts & Up – Here is where we move out of the portable generator territory and head over to the standby units. Most people won’t need a size this high, especially if they are just getting through a couple of days while their power comes back on. However, if you are looking to power your whole home then you may want to look at a full standby generator and having it wired directly to your home.

Lastly, please note that when looking at generators there are two numbers that you’ll notice. The first is known as the ‘Maximum Power.’ The maximum power is the very max power output that the generator can produce. This maximum level can usually only maintain for about a half-hour. The second measurement is known as ‘Rated Power.’ The rated power is around ninety percent of the generator’s full power. This power level can be maintained for much longer periods of time. When looking for the perfect sized portable generator then you definitely want to review the rated power rather than the maximum power.



Well folks I hope now that after reading this article you feel a lot more comfortable when it comes to looking at generators. If you find yourself still confused or you are having trouble finding the watts on your appliances feel free to reach out to me by visiting our contact page and we’ll do our best to help you through it. Please note, that this is a guide and the ultimate decision on the size of your generator is up to you.

Thanks for reading,

Alec Johnson


You may also like