Earth Day spurred some conversation on NTEN Discuss [1] about how to figure out carbon emissions for every watt a computer uses per hour. Dean Matsueda wrote that he had seen and used carbon-footprint calculators online to gauge household, car, and air travel C02 emissions but would like to drill down to more specifics, like computer use.

Walt Daniels gave this response:

Carbon footprint is a simple multiply if you have the watts/hr and number of hours. watts/hr is what is hard to come by for most computer setups unless you have a meter on it because the usage depends on too many things,like duty cycle and how you have the power savings features on your computer set.

Gavin Clabaugh lets us know that to do it right, you need to meter the machine. He uses a Kill-A-Watt [2] (a simple one costs about $20).

And Dave Shaw, H4 Consulting, added:

You're right, there are a lot more variables to take into account. The amount of carbon emitted by a power plant depends a lot on the source - from 2.0 lbs per kilowatt-hr for coal, to 1.3 lbs per kilowatt-hr for natural gas (because natural gas is partly hydrogen, and coal almost all carbon). See the US Estimated CO2 Emissions [3]

One usually sees an average of 1.5 used, but that depends on the mix, of course. Here in the Northwest it will be lower because of a larger percentage of hydro than elsewhere, and France will be drastically different because of the dominance of nuclear plants.

Then of course, it depend on the computer, as Walt points out. The nameplate power usage will be a maximum, and it will use much less with the monitor off and on standby.

FYI, a watt is a measure of energy per unit time, energy flow. The usual measure of electrical energy is the kilowatt-hr (kwh) equivalent to a 1000 watt appliance on line for 1 hr. Depending on what average you choose, that will generate 1.3 to 2 lbs of carbon.

The number of variables is why you don't see a "computer carbon calculator". The usual online carbon footprint calculators do a grand summary for the whole house.

Ann Yoders, Community IT Innovators [4], has developed a tool to do this as they move into green technology consulting this year. If you want to ping her, she says she can connect you with their consultant. She adds, "Though not 100% confirmed as of yet, we're moving in the direction of turning this into a web application so hopefully what is now an overwhelming experience in trying to track this info down will be much easier." Basically, you'll lessen your carbon footprint if you turn your computer off when you are not using it!

In other Affinity Group News, a new Drupal Group [5] was added by Johanna Bates and the conversation is already rolling. 501 Tech Clubs have been active with post-NTC events coming up in San Francisco [6], New York [7], DC [8], and Portland [9] to discuss the top 3 takeaways from the NTC. The Austin 501 Tech Club [10] had their post-NTC event last week and now has a profile on Facebook [11].

Interested in joining the Drupal Group [12], a 501 Tech Club [13] in your area, or another Affinity Group [14]? Go ahead: it's free and open to everyone at http://groups.nten.org [15].