Back in 1784, hanging out in Paris and heady with Enlightenment, Benjamin Franklin had an idea. Struck by the fact that Parisians were sleeping during sunlight hours and then staying up late at night by candlelight, he calculated the number of candles that were being wasted — and came up with an impressive number, 64 million pounds worth of them. Franklin therefore jokingly proposed a massive schedule change, noting that a fortune could be saved through “the economy of using sunshine instead of candles,” and even suggested at one point that perhaps cannons be fired at sunrise to get everybody out of bed.
But there’s a problem with this (well-lit) practice. It is increasingly looking like Franklin’s idea about saving energy was wrong. Genius though he was, he seems to have forgotten one thing: Moving around daylight hours doesn’t only change how much people need to rely on artificial lighting, whether in the form of candles or modern halogens. It also changes the overall complexion of temperatures that we experience while we’re awake. And in an age of heating and air conditioning, that may cause us to reach for the thermostat — with big, probably negative nationwide impacts on energy use, greenhouse gas emissions, and your wallet.
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