What Size Generator Do I Need?

In a world that runs on constant power, a generator is an essential piece of equipment. Whether you are a frequent camper or live in an area that experiences frequent power outages from inclement weather, owning a generator ensures that you can stay connected whenever and wherever you need it.

Shopping for a generator can come with its challenges as you navigate all the different types on the market. One of the most important considerations when choosing a power generator is size. Learn more about generator sizes and how to choose the right size below.

Why Does Generator Size Matter?

All generators generally work the same way. They convert mechanical energy (the energy of movement) into electrical energy to charge your electronics and/or run tools and household appliances. The process is similar to what happens in a typical gas-powered car. The two main components in a generator are an engine and an alternator. The engine spins a rotor within the alternator, creating an electrical current. That current gets sent to a control panel to power your electronics. Some sort of fuel is required to get the engine going. Typically gasoline is used, but if you want the freedom to use both gasoline and propane, learn about dual fuel generators on our blog.

Why does the size of the generator matter? Size essentially dictates the generator’s power output. The bigger the generator, the more electricity it can put out, which matters based on your personal needs. While a smaller generator can easily charge your phone and laptop, it doesn’t have enough wattage to be a home generator.

Understanding Wattage

The amount of electricity required to run an electronic device is measured in watts. Determining the wattage of all the items you plan to plug into your generator is key to choosing the right generator. A generator that doesn’t provide enough wattage for all your devices can leave you struggling. Even more confusing, wattage comes in different forms.

Starting Wattage

Rated or running watts is the amount of power needed to get a device or appliance started. Most electronics require more starting watts to turn on and less wattage to stay on. That may not be an issue if you are simply plugging in a few mobile devices, but for a whole house generator, a full power outage can take out a lot of major appliances that are normally constantly on, like your refrigerator and HVAC system. All those appliances starting back up can cause a surge that your generator needs to deal with.

Running Wattage

Rated or running watts is the power required to keep a device or appliance that is already running steadily. As mentioned, this is typically lower than the starting wattage. Most appliances list their running wattage to help consumers determine their power needs.

Surge or Starting Watts

Surge watts are very similar to starting watts. Some appliances in your home contain small motors. This includes your furnace and your refrigerator. Getting all of those motors started after a power outage requires an extra bit of electricity. This is known as surge wattage.

Determining Your Total Wattage

Calculating the total wattage of all the appliances and devices that you plan to plug into your generator determines the type of generator that you ultimately end up with. That may not be much of a problem if you are only charging smaller electronics. Even small portable generators will provide a little less than 3,000 watts. To give you an idea, the average 15-inch laptop requires about 60 watts per hour, while a smartphone uses about two to six watts per hour while charging. That is fairly negligible. If you need a generator just for charging devices, keeping lights on, and even running your refrigerator during emergencies, a portable generator is a perfect option. 

However, if you need a full backup system to power your entire home during a power outage, you should start looking into a whole house generator. Whole house generators also come in various sizes based on the wattage requirement. To help you determine the wattage that you need, here are some common household appliances and their average running wattage per hour:

  • Table lamp: 150 watts
  • Video game console: 200 watts
  • Television: 100 to 350 watts
  • Washing machine: 750 watts
  • Coffeemaker: 400 to 800 watts
  • Refrigerator and freezer: 600 to 800 watts
  • Microwave: 1,200 watts
  • Hot plate: 1,250 watts
  • Space heater: 1,250 watts
  • Vacuum: 700 to 1,400 watts
  • Hairdryer: 1,200 to 2,500 watts
  • Toaster: 1,100 to 1,700 watts
  • Personal desktop computer: 500 to 2,000 watts
  • Electric range stove: 2,500 watts (for one element)
  • Clothes dryer: 1,800 to 5,000 watts
  • Electric oven: 5,000 watts

The general rule of thumb here is that if the appliance generates heat, it probably has a higher wattage.

Here are some common home systems and their average power requirements:

  • Outdoor lighting: 500 to 1,000 watts
  • Radiant heater: 1,300 watts
  • Window air conditioning unit: 600 to 1,500 watts
  • Sump pump: 1,500 watts
  • Central air conditioning: 4,000 to 8,000 watts
  • Water heater: 3,000 to 4,500 watts
  • Electric furnace: 5,000 to 25,000 watts

Note that these are merely average running wattages. Check your individual appliances for exact wattage requirements. Add the starting wattage for all your appliances. This gives you a good idea of the highest potential wattage output that you’ll need.


Overloading or overheating your generator can potentially be disastrous. Most generators have an automatic shutoff function as a safety precaution in the event of overloading. While this prevents issues with your generator, your appliances may get damaged from a sudden shutoff.

Constantly stressing your generator with high energy demands can increase the risk of malfunctions. Your generator may require more regular maintenance and repairs. As a general rule of thumb, choose a generator that can handle your power needs without exceeding 80 percent of its own capacity.

Why Not Start Big?

It can be easy to overload an under-powered generator, so why not just start with a big generator? Bigger isn’t always better here. Whole house generators have fairly high upfront costs, which include the generator itself and the installation costs. Factor in ongoing maintenance and the cost of fuel, and the costs may exceed your overall budget. 

Those costs become even more exorbitant if you find yourself barely using your generator. A whole house generator is ideal for frequent power outages that last several days at a time. If power outages are rare or if you just need some peace of mind in the event of an emergency, it may be better to go small with a portable generator. 

A power generator can be an important tool for your safety and peace of mind, but choosing the right generator for your needs can be difficult to navigate. The size of your generator ultimately comes down to wattage and your general usage requirementsts, along with your personal budget. For a portable home backup generator to power your entire home, factor in the wattage of all of your home appliances and home systems to prevent a potential overload.

Find the Right Generator for You

At DuroMax, we have many types of generators, from portable home backup generators to inverter generators. Are you ready to use your generator during a power outage? Our generators are reliable and ready for any emergency. Are you looking for your first generator but wondering how much a generator is? DuroMax has a generator to satisfy your budget. Explore our DuroMax generators, engines, pressure washers, and more today.