The Surprising History of Light
by Mike Troupos
Did you ever get yelled at by your parents to “Turn the lights OFF!” when you were a kid? I did. As an energy engineer as an adult, I wish I could have shown my kid-self the calculations on how much it really costs to leave the lights on. A new LED lightbulb uses roughly ten watts. If you left it on all month, it would cost you about $1. You read that correctly; if you never turn the lights off, you add a meager dollar to your electric bill. Now, even if I could do that math as a kid, I still think my parents would have gotten after me just on principle.
It might be unsurprising to you that we can get electric light for only a dollar for an entire month. But you might find it surprising that cheap light has only been around for about 100 years – a blink in the span of history. In my own right, I am an energy nerd who pays attention to the cost of light, but William Nordhaus is an energy nerd who puts me to shame. Nordhaus wrote a paper in 1998 that covers the history of light sources and the labor associated with each source.
The first lighting “technology” was burning wood. If you spent one hour chopping wood, the wood you get would produce less than one minute of a light bulb's light today due to the flickering and inconsistencies. Technology advanced to the point where the Romans used oil lamps. Nordhaus bought one of those thousand-year-old lamps and measured how much light you got from it relative to the sesame oil you poured in. It was significantly more efficient than burning wood. The next technological leap was candles. In the 18th century, one hour of wages spent on candles would get you 14 hours of illumination (though dimmer than a light bulb today). That is 14 times better than wood but nowhere close to today's efficiencies.
Other technologies continued to build on the success of oil lamps like kerosene and gas. However, the real acceleration came when Thomas Edison harnessed electricity and invented the lightbulb. That light bulb was 100 times brighter than a candle, and running it for four hours came close to an hour's wage. The lightbulb was genuinely revolutionary and justifiably regarded as so. However, over the last 120 years, iteration has made it substantially more efficient than the original. First, technologies like fluorescent came along; now, LED reigns supreme as the most efficient technology for illumination.
Nordhaus followed lighting technology from wood to CFLs in much more detail than I talk about in this article. His findings (Back in 1998) were that 1 hour's worth of work would buy you 350,000 times more illumination than you could buy in ancient Babylonia. In fact, with LED technology today, we can get over 1 million times more illumination than 3,000 years ago for the same amount of resources. Not to mention, there are no fire hazards or indoor air quality issues with the illumination technologies today.
When my baby daughter is old enough to leave the lights on, I will take a different approach than my parents. Instead of yelling at her to turn off the lights, I will tell her that those moments of wasted light are equivalent to what our ancestors would have consumed in a lifetime. Sometimes it just takes a little perspective to help us feel gratitude.