Energy use is all the rage these days -- but few people know how to read their own electricity meters. Here's how you can find out your live use, in watts, with a little help from Wolfram Alpha.

If you're like most people, you have an analog meter that looks something like the attached photo. It features several clock-like dials, a bunch of numbers and codes, and a spinning*ferraris*disk that should be rotating now, if you're using any electricity at all in your house. You'll need to find one key number on your meter. Let's call it the

**multiplier**. It's usually labeled with

**Kh, Kp, or Ka,**and is typically

**6 or 7.2**on homes in the United States. For our example, we'll assume it's 7.2. The multiplier is equal to the number of watt-hours of energy that pass through your meter per revolution of the spinning disk. Without getting lost in energy units, take a close look at your meter's disk. You'll notice it's got a mark on it (or many marks) that you can use to count revolutions. With a stopwatch, time how long it takes for one revolution (rev) of your disk, in seconds. Let's say it takes 15 seconds for your meter's disk to complete one rev. Type the following into wolfram alpha:

**[multiplier]**watt-hours per

**[time for one rev.]**seconds in watts

**7.2 watt-hours per 15 seconds in watts >**

Ta-da! You get an answer in watts -- 1,730 watts. If your energy use remains constant for 1 hour -- you will have used 1.73 kilowatt hours. A typically kilowatt-hour costs around $0.15 in the northeast, so you just spent nearly 30 cents on electricity. If you try this out, post your results in the comments! Now, as you can imagine, wattvision simplifies this procedure quite a bit. More on that soon! ;)