Mega Question: What’s a Watt?



Have your kids ever asked you, “How much is ten zillion trillion dollars?” Well mine have, and rather than try to explain large numbers to a young mind, I usually just respond “It’s A LOT.”

I will attempt to do the same with electricity below.


The watt is a derived unit of power defined as joule per second and can be used to express the rate of energy conversion or transfer with respect to time. For example, a 60-watt bulb will use 60 watts of energy per hour.


The kilowatt is equal to one thousand watts. In 2014, the average US home uses 10,932 kilowatt-hours (kWh) per year, an average of 911 kWh per month.


The megawatt is equal to one million watts. Think of your electric clothes dryer. The average dryer uses 5,500 watts (if the dryer runs for 1 hour). IF you ran your dryer nonstop for 7 ½ days, you would use 1 megawatt of energy.


The gigawatt is equal to one billion watts or 1,000 megawatts. This unit is often used for large power plants or power grids. Think of Times Square in New York. At its peak, Times Square (and the surrounding theater district) uses around 161 megawatts (about 16% of a gigawatt).

Most importantly, 1.21 gigawatts is what Marty needed to get “Back to the Future!”


The terawatt is equal to one trillion watts. Worldwide power usage is commonly measured in terawatts. The average lightning strike peaks at 1 terawatt, but these strikes only last for 30 microseconds.


The petawatt is equal to one quadrillion watts. The total power of sunlight striking Earth’s atmosphere is estimated at 174 petawatts.

The Star Killer Base in Star Wars: The Force Awakens generated 1 petawatt of energy.

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