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running watts vs starting watts: the differences

posted in 03/26/2024
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When you’re shopping for a new appliance or a generator for use with older appliances, you’ll likely come across two key terms: starting watts and running watts. These terms are used interchangeably and provide important information about a device’s power or energy consumption under various conditions..

When selecting a new generator, it is important to consider the power requirements of the equipment and tools you intend to use. If the initial wattage needed by an electronic device surpasses the AC output capacity of the generator, you won’t be able to power it on.

Let’s take a look at the difference between running wattage and starting wattage, and how these values affect a device’s suitability for use with a generator

BISON explains the difference between starting wattage and running wattage generators and how to use them to choose a generator that suits your requirements.


what are the running watts and starting watts of a generator ? 

Running watts, also called rated watts, represent the number of watts a device consumes continuously during operation. This generation of electricity usually lasts for a long period of time, usually measured in hours.

Starting wattage, also known as peak or surge wattage, represents the instantaneous additional wattage required by a generator to start equipment, constituting the maximum wattage the generator can produce, usually quantified in seconds or minutes.

A brief burst of extra power (lasting only a few seconds) is the difference between starting power and running power. Each device has different operating and starting wattage requirements. Not all devices require this surge to turn on. The startup wattage of some devices can be more than double the amount of electricity used during normal operation.

how do I calculate running watts and starting watts?

In just a few steps, you can estimate the wattage your appliances will need to start up (surge wattage) and how much power they’ll use while running (running wattage).

Step 1. Find the wattage ratings of the appliances you want to use with the generator. This information is usually on a label on the appliance itself.
Step 2. If the label only shows volts and amps, you can calculate the watts using this formula: watts (W) = volts (V) x amps (A).
Step 3. Once you have the running wattages of all your appliances, add them together. This total should be less than the generator’s output capacity to ensure it can handle the load.
Step 4. Identify the appliance with the highest starting wattage. This is the surge of power it needs when first turned on. Add this number to the total running wattage from step 3.
Step 5. The final sum is the estimated total starting wattage you’ll likely need from your generator.


how to calculate total running and starting watts requirements

Appliances need different amounts of power to start up (surge) compared to how much they need to run continuously. Some appliances use the same amount of power for both, while others require a burst of extra power just to get going. This extra starting power can be more than double the running wattage.

To choose the right generator for your needs, you’ll need to consider both the total running watts and the starting watts of all the appliances you plan to use at once. Here’s how to figure it out:

#1. Find appliance wattages: Check the label on each appliance you want to power with the generator. It should list the running wattage and sometimes the starting wattage as well. 

#2. Convert volts/amps to watts (if needed): If the appliance label only shows amperage (A) and volts (V), the formula Watts (W) = Volts (V) x Amperage (A) can be used to calculate the number of operating watts.

#3. Add up running watts: Make a list of all the appliances you want to use and add up their running wattages. This total should be less than the running watts capacity of your generator to avoid overloading it.

#4. Factor in starting watts: Find the appliance with the highest starting wattage. Add this number to the total running watts you calculated in step 3.

#5. Total starting watts: This final sum is the total starting watts your generator needs to handle. Make sure the generator you choose has a starting watt rating that’s equal to or higher than this number to prevent overloading during startup.

Operating Watts and Starting Watts of Common Household Appliances (for reference only)

ApplianceOperating Watts (Approx.)Starting Watts (Approx.)
Microwave Oven600-15001000-3000
Air Conditioner500-15001200-3000
Washing Machine350-5001000-2000
Clothes Dryer1800-50001800-5000
Coffee Maker800-1200800-1200
Electric Kettle1000-15001000-1500

how to choose the correct wattage?

Don’t be fooled by the numbers in the generator name! It usually reflects starting wattage, the burst of power upon initial use, rather than the wattage it can deliver continuously. To make sure it meets your needs, check your generator’s operating power specifications. This number represents the actual continuous power the generator can provide.

You might think that a 4000W generator can run 4000W appliances, but this is not the case. Don’t worry though, starting wattage is still important as you need enough power to keep everything running smoothly.

While running wattage and starting wattage may seem confusing, they actually help prevent circuit tripping, which is great news! Here’s how to find them:

  1. Operating Wattage: Add up the wattage of all the appliances you wish to run at the same time. This total is your operating wattage. To achieve the advertised generator run time, BISON recommends that you run the generator at approximately 75% of its capacity.
  2. Starting Wattage: Find the device with the highest starting wattage requirement. Add this number to your total operating power. This sum is the maximum starting wattage, which needs to be less than the rated starting wattage of the generator.
  3. Find the right generator: Filter generators by starting power and operating power. Find the model that meets your power requirements.


When using a generator to power equipment, it is important to consider its operating and starting wattage. While some devices may operate at only 700 watts, this may briefly increase to 2200 watts when powered on. This difference is especially noticeable in equipment with motors.

It is also important to consider the total output power of the generator. A generator with a higher output can accommodate more appliances and tools.

Make sure your generator or any alternative power source has enough surge capacity to handle the initial power surge required by your off-grid equipment.

running watts vs starting watts FAQ

Appliances require a certain amount of extra power to start, kind of like a jump starter. This initial surge is called cranking watts, also known as peak watts or surge power. This is also important for generators as this determines how much power they can provide during the start-up phase. Once everything is running smoothly, both the appliance and the generator use a lower amount of electricity, called operating wattage.

The easiest way to determine the wattage an appliance is running at is to multiply the amperes by the volts. This applies to most appliances.

However, large appliances with motors, such as refrigerators and air conditioners, require additional power to start. This surge is also called cranking wattage and is typically 1-2 times the operating wattage of the device.

You can usually find wattage information directly on the device itself or in the user manual.

The average U.S. household uses approximately 29,130 watts of electricity per day, but this may vary based on your equipment and habits. For example: Large, older refrigerators use more watts than smaller, newer refrigerators. Running your air conditioner throughout the day uses more watts than using it for short periods of time. More people usually means more appliance usage.

So, while 29,130 watts is a good average, it’s important to consider your specific situation to get a more accurate idea of your home’s wattage needs.

Generators are rated based on their starting and operating power, allowing users to evaluate their ability to provide power during startup and continuous operation. This distinction also helps determine how many devices can be powered simultaneously. Essentially, a generator with higher starting and operating power can accommodate a greater number of devices.

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