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Previously I wrote with Sharon Kyle in the LA Progressive about power plant emissions for a whole home.

shower head

Now I will go inside the home, and also simplify things so that you can do rough calculations in your head for both energy cost and pollution. In other words, you will get a better handle on things that your energy provider may not really want you to understand.

For a typical Los Angeles utility user, it turns out that using one watt continuously for one year costs about one dollar. Hence the “Buck A Watt” name.

This comes in handy for calculating the cost of running small appliances that are always drawing power, such as chargers (usually a couple watts) and cable boxes (around 100 watts). But that doesn't say anything about the resulting pollution. An efficient power plant generates one pound of carbon dioxide (CO2) per kilowatt hour (old coal plants generate much more CO2). A kilowatt hour is the energy used by a 1-watt device in 1000 hours (more than a month), and it is usually abbreviated as “kWh” on utility bills. That 1-watt device uses 8.7 kWh in a year, so it costs a dollar and generates about 9 pounds of carbon dioxide. That CO2 has about the volume of a shower.

So now we've expanded the rule for a watt for a year: it costs a dollar and the CO2 would fill 1 shower. So the rule now becomes the “Buck and a Shower a Watt”.
What about those things that don't run all day? Since the rule is simple, it can be scaled to fit other uses. If you have a common 12 Watt CFL lightbulb and you run it about 2 hours a day, that is about one tenth of the 24-hour day, and so it consumes about as much energy as the 1-watt device that is on all day. So it costs a buck and a shower.

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[dc]H[/d]cow about that 1200-watt space heater that runs 2 hours a day on about 30 cold days a year? Now things gets trickier. It is running for about one tenth of the months of the year for about one tenth of the day, so divide the watts by 100. That's 12 bucks and 12 showers full of CO2.

scott peer

Using the Buck and a Shower a Watt rule can help you make sense of what the true costs are of the things you plug in. Enjoy your savings!

Scott Peer

Scott Peer worked as an engineer in the aerospace industry for decades, contributing to several NASA projects including the Cassini Mission to Saturn and Spitzer Space Telescope. He noticed that as we accumulate more and more science data, we are not taking more actions to reduce the causes of climate change. So he changed fields, and is now an entrepreneur in the energy efficiency field.

Posted: Monday, 10 July 2012