February 15, 2017

How the cost of light has fallen by a factor of 500,000

By Maximilian Wirth
As the BBC recently pointed out, our prehistoric ancestors needed to gather and chop “wood 10 hours a day for six days… [in order to] produce 1,000 lumen hours of light… That is the equivalent of one modern light bulb shining for just 54 minutes, although what you would actually get is many more hours of dim, flickering light instead.”

Even when better alternatives, such as candles, became available, it was still prohibitively expensive to light the house for the common person. Further, the first candles were produced from animal fat and not from the clean burning paraffin wax we use today, producing a flickering smelly flame.

It wasn’t until the 18th century that spermaceti candles, which were made from a waxy substance found in the head cavities of sperm whales, and were much less time-consuming to produce, became more readily available. But even then, reading light remained very expensive (not to mention terminal for the whales). George Washington calculated that five hours of reading per night cost him £8 yearly - well over $1,000 in today's dollars.

The light bulb changed everything.

By 1900, 60 hours of work could provide 10 days of light. The light bulbs would burn 100 times as bright as a candle, steadily, and inodorously. By 1920, 60 hours of work could already pay for 5 months of stable light. By 1990, that increased to 10 years of light. Today? 52 years.

And progress has not stopped yet. LED lights continue to become cheaper and cheaper.

The amount of labor that once bought 54 minutes of light now buys 52 years of light. The cost has fallen by a factor of 500,000 and the quality of that light has transformed from unstable and risky to clean, safe, and controllable.

Like a myriad of other products we take for granted today, light has turned from something too precious to use into something everyone can afford.