starting watts vs running watts

Starting Watts Vs Running Watts – Generators Master

What is the difference between starting and running watts? This is the most common question asked by consumers. Here we will answer this question as best we can.

In order to answer this question, we must understand what wattage means. A watt is the amount of power required by any electrical appliance to perform work in a unit time.

power = work done / unit time 

Starting Watts/Running Watts Definition

Motor-driven devices require extra power for a few seconds to start and then a constant amount of power thereafter. 

The additional watts required to start an appliance for a few seconds are known as starting watts, surge watts and peak watts

After the appliance starts, it needs to be supplied with a constant amount of power to work smoothly through its runtime. That continual power supply is called running watts, and it is also called rated watts.

What does starting watts mean on a generator?

Generators are rated in two wattages: starting wattage and running wattage. The starting wattage is the surge power that the generator can provide to the appliances that require extra watts in order to begin running. With a running wattage, the generator delivers energy continuously throughout its runtime. 

Disclaimer: All the starting and running wattage values are best estimates based on averages. For accurate wattage, see your appliance’s label, or if it is not available, contact an electrician for help.

Starting Watts For Refrigerator


Several types of refrigerators exist, including French door, wine refrigerator, side-by-side refrigerators, etc. They all require different starting and running wattages. A refrigerator freezer of average size requires 1200 surge watts and 800 running watts.

Starting Watts For AC

Split AC

There are many types and sizes of air conditioners, depending on where they will be used. These include split air conditioners, central air conditioners, window air conditioners, etc. They are also labeled in sizes like 1 ton, 1.5 ton, 2 ton or in units like 12500 btu, 15000 btu. 

Each type has a different starting wattage and running wattage. Window air conditioners typically draw 1800 starting watts and 1200 running watts. 

The question is also asked, how many starting watts for RV ac? In most RVs, 12500 btu air conditioners are used. These air conditioners require 1800 starting watts and 1200 running watts.

How many watts does a water pump use?

Sump Pump / Well Pump

There are different types of water pumps, and their horsepower also varies. Water pumps include well pumps, and sump pumps. They have different sizes and as a result they need different starting watts and running watts.

Starting Watts Sump Pump

A sump pump is a pump that is used to remove the accumulated water from a sump basin in a basement.

ApplianceRunning wattsStarting watts
Sump Pump 1/3 HP8001300
Sump Pump 1/2 HP 10502200
Sump Pumps Starting/Running Watts

Starting Watts Well Pump

ApplianceRunning wattsStarting watts
Water Well Pump 1/3 HP10002200
Water Well Pumps Starting/Running Watts

Starting Watts For Air Compressor

A compressor is a mechanical device that reduces the volume of air inside a container to increase its pressure.

There are different horsepower sizes of air compressors, such as 1/2 HP, 1 HP, 1.5 or 1-1/2 HP, and 2 HP.

ApplianceRunning wattsStarting watts
Air Compressor 1/2 HP 10002000
Air Compressor 1HP15004500
Air Compressor 1-1/2 HP 22006000
Air Compressor 2 HP 28007700
Starting Watts and Running Watts of Air Compressor

Starting Watts For A Coffee Maker

Coffee makers are kitchen appliances that brew coffee automatically. Depending on the size of the coffee maker, a coffee maker draws 700-1200 running watts. This appliance does not require surge power.

Starting Watts Chart

ApplianceRunning wattsStarting watts
Window AC12001800
Well Water Pump10001500
Sump Pump8001200
Refrigerator Freezer8001200
Computer 800
Electric Drill600900
Television 500
Deep Freezer 500800
Common Light Bulb75
Air Compressor (1HP)15003000
Starting Watts and Running Watts of Appliances

How to calculate starting watts if it is not mentioned on appliances?

Using the following simple formula, we can calculate the starting wattage of different appliances.

V x I = W

V is the input voltage, I is the input current, and W is the amount of power consumed by the appliances. 

You can find the input voltage and current on the label located mostly on the back of the appliance. If this information is not available, you will have to use an ammeter, and a voltmeter to calculate current and voltage. These numbers can be used to calculate running wattage. 

In most cases, starting watts are an additional 0.3 of running watts, and can be calculated using the formula below.

Starting watts =  running watts x 1.3

Example: Consider an appliance whose input current is 6A, and whose input voltage is 120V.

Running watts = 120 x 6 = 720 watts

Starting watts =  720 x 1.3  = 936 watts 

Therefore, in this example, the appliance requires 936 starting watts and 720 running watts.

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