When people talk about saving energy or generating power through renewable sources like wind and solar, they use terms that can be confusing like watt and kilowatt hour.  Even worse, the media and sometimes the “experts, misuse the terms.  I was recently at the Boston Museum of Science with my son and we had some fun with the “What’s a watt?” exhibit, that .  If you get a chance, the Museum of Science has a ton of exhibits on savings, storing and producing clean energy that are well worth checking out.  Read down for a quick lesson on electricity and watch the video at the end.

What's a Watt

Young Medford resident learning about electricity at the Boston Museum of Science

In technical terms, watt (W) is the measure of power, or the rate at which you do work measured in J/s (that is Joules per second) and watt-hour (Wh) is the measure of energy, or the potential to do work.  Don’t worry if this didn’t help, because I am going to make it more tangible in a moment.

Understanding the Demo

The amount of water contained in a bucket (tube) in gallons in this example can be through of the amount of electrical energy or watt-hours available.   The speed (rate) at which the waters flows out of the tube is the power or rate of electricity consumption.  In this example we consider the tube when full as having 10 Wh of energy.  We have two loads to experiment with: an electric mixer rated at 250 W and a hair dryer rated at 1,000 W.

When we turn on the hair dryer, notice how fast the water drains out of the tube.  That is the power (or flow of energy) in this case.  Doing a little math, we can calculate that at 1,000 W the hair dryer will use up 10 Wh of energy in 26 seconds.

10 Wh = 3,600 sec/hr X 10 Wh = 36,000 Ws
36,000 Ws / 1,000W = 36 sec

If we use the electric mixer instead, it uses one quarter the electricity as the hair dryer and would take over 2 minutes to drain the 10 Wh from the tube.  Now enjoy the short video and feel free to ask any further questions you have in the comments.

used with permission from Green Lifestyle Changes

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