Generator Starting Watts & Running Watts 2023 [The Difference Explained]

What is the difference between starting watts and running watts?

Starting watts are the power amounts that appliances require to start their electrical system motors and turn them on, usually taking between the first 10 and 30 seconds. On the other hand, running watts are the power amounts that appliances require to run continuously after switching them on.

I still remember when I went out with my dad to check out generators we could buy for our farm and the confusion I had when looking through them because I saw two wattages mentioned: starting watts and running watts.

These wattages are very important to know, and they led me to do some research on them. The aim of this article, therefore, is to give you an idea of what these terms mean and the differences they have from each other.

Do all electrical appliances use starting and running watts?

No, they do not. Some appliances rely on the same power wattage to start and run, while others split their wattage requirements into starting and running watts.

Because of this distinction, knowing which appliance you are dealing with is helpful. It will help you understand the power amounts you consume, if you need to adjust your power consumption and what appliances you prioritize when making power consumption changes.

There are two kinds of appliances when considering whether they rely on starting and running watts. They are:

Reactive loads: These appliances use more power when they start and maintain a certain lower power usage as they run. These appliances have electric motors, and their starting power is usually three times the running power required. They include water pumps, generators, refrigerators, freezers, and AC heating and cooling systems.

Resistive loads: These appliances operate and start using the exact power wattage requirements. They will shut down and start almost immediately, most of which are used in lighting, heating, and heat production.

They also only rely on active power, meaning the power source supplies electrical currents directly to them, and no electric current flows in reverse. They include light-load devices such as TVs, laptops, computers, dishwashers, and coffee makers.

Starting watts vs. Running watts

If you own an electric appliance that uses a lot of power, like a refrigerator or a home electric AC system, you may notice the starting watts printed on the device. This refers to the appliance’s power requirements to start the reactive load. For instance, a generator with a starting wattage rating of 4500 watts can give the electrical motor and internal electric components a maximum of 4500 watts for up to 30 seconds.

Running watts are another rating you must know if you own a large electrical appliance. Unlike the starting wattage that is only needed for a few seconds, running watts are required to keep the device operational throughout its run.

Specific devices like inverter generators will also have engines operating at variable speeds, which regulate the running watts depending on the demand of the device, in contrast to conventional generators with constant levels of running wattage.

Difference between starting watts and running watts

Running wattsStarting watts
It ensures the appliance remains running as long as you need



It ensures the electric motor in the appliance has enough energy to power on and on all the electrical parts in it.
Both reactive and resistive loadsneed it.


Reactive loads only need it.

It is required as long as the appliance is on and operational.The appliance only requires it during the first 30 seconds.

Tips to tracking the appliance wattage you need

It is understandable if this information seems overwhelming. Still, there are tips to ensuring you know the wattage your home appliances require without exposing them to the risk of power surges. To calculate your power needs easily, you should:

  1. Start with listing all the electrical devices you use and their wattages. The user manuals will contain this information if the wattage is not printed and stuck on the device.
  2. Add the watts you have listed, and the total will be for the running watts.
  3. If you have a generator, compare the running watts of the generator (what it is capable of supplying to the devices) and the total running wattage figure from your devices. To be safe, experts suggest that the running wattage from your electrical devices must not exceed 75% of the running watts from the generator.
  4. Afterward, examine the starting watts for all your major electrical appliances and see which appliance has the highest starting wattage. Add this wattage value to your running watts, then compare the total to the generator’s maximum starting watts. To be safe, the total value of running and starting watts must not exceed the generator’s full starting watts.

Other tips you can use are:

  • Reduce the starting wattage requirements by powering the appliances on, starting with the appliance that needs the highest starting wattage and ending with the device that requires the lowest starting wattage.
  • If you own a generator and need it to power a significant area, such as an office building, several people will likely use the power supply at any time. It is always best, in this case, to get a large generator because it will have a very high starting wattage and is better equipped to handle power surges when many people simultaneously use a particular power source.


Wattages can be confusing to understand, but they are always helpful to know because you can handle the electrical demands of any electrical device you own and regulate the power usage you rack up every day of the year.


How can I calculate my starting wattage requirements?

If the device’s user manual does not indicate this information, you can use this formula to calculate it: AMPS X VOLTS = WATTS. Additionally, you can estimate the starting watts as 1 or 2 times the running watts.

What generator wattage size do I require to run my house?

The power requirements your home needs depend on the electrical devices you use, but in most cases, you should get generators with a rating between 5,000 and 7,500 watts. This is enough to power essential home devices like water pumps, freezers, and refrigerators.

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