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Energy by the numbers

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A lot of our discussions about energy policy involve adjectives. Solar power has big potential. Biofuels don't prevent that much carbon from entering the atmosphere. China and India are consuming huge amounts of oil.

To University of Cambridge physicist David MacKay, this is just fact-free blathering. After all, how much is "big"? How big is "huge"? Unless we can express these concepts in numbers, we have no basis for comparison.

Mr. MacKay wants to cut through what he describes – in a way that only an eminent British physicist could – as "crazy innumerate codswallop." In his forthcoming book, "Sustainable Energy – Without the Hot Air" – a draft of which can be downloaded here – MacKay shows how to estimate those numbers and convert them into a human-scale unit of measurment: the kilowatt-hour.

One kWh, says MacKay, is roughly the energy consumed by burning a 40-watt lightbulb for an entire day. Burning a gallon of gasoline produces about 40 kWh. Flying 8,800 miles on a fully-loaded 747 uses 12,000 kWh. Taking a bath uses 5 kWh. And so on.

The "typical affluent" Briton, MacKay says, consumes 200 kWh per day. The average American consumes 300 kWh per day.


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