The Magical Power of the Kilowatt-Hour
Guest essay by Tom Scott
The typical follower of this blog is likely more knowledgeable in math and the sciences than the average reader, so many of you will find the following quite obvious on an intellectual level, but the facts below may still stimulate a new awareness of just how powerful is the concept of energy available at the flip of a switch.
The incentive to write down these brief thoughts came while reading from Dr. Roy Spencer’s blog the other day. There I came across this stupefyingly dumb quote from our White House Science Advisor, John Holdren . In a 1975 newspaper article in the Windsor Star, entitled “Too Much Energy, Too Soon, a Hazard”, he wrote:
“Finally, less energy can mean more employment. The energy producing industries comprise the most capital intensive and least labour intensive major sector of the economy. Accordingly, each dollar of investment capital taken out of energy production and invested in something else, and each personal consumption dollar saved by reduced energy use and spent elsewhere in the economy will create more jobs than are lost.”
To evaluate the above quote, consider the difference in productivity between the solar and coal power production industries. Both industries support about 174,000 jobs in the U.S. while coal provides about 150 times more power at this time (about 0.25% to about 39%). Hardly a winning substitution.
But can’t we (or the third world) live just as well without electricity?
To answer this, lets start with the term “horsepower” as it is rooted in real-world imagery. One horsepower is defined as 550 pounds of force displaced one foot per second. In other words, with one horsepower at hand one could start at sea-level and lift a 550 pound weight 1 foot higher every second. It was thought that a horse could do this kind of work on a reasonably regular basis, thus the name. On the other hand, it is hard to imagine a human generating this kind of power for more than a few seconds at a time.
It so happens that a kilowatt is about 1.34 times “larger” than a horsepower, or about 737 lbs raised one foot each second, or 100 kg raised 1 meter each second. If we assume than our electric motor and transmission are about 75% efficient (1/1.34), we would be right back to an output of 550 ft-lb of useful work from each KWH purchased. For each KWH we pay about 0.10 to $0.15 at retail prices here in the U.S.
The U.S. median household income is about $50,000 per year, which spread over 2,000 work hours would be $25 per hour. Historically an employer has loaded costs of about 1.4 times the pay rate, so the cost to the employer would be about $35 per hour. How does that wage compare to the work which can be done by the kilowatt-hour? At a price of 10 cents per unit, an employer could substitute 350 KWH for each man-hour of payroll. Assuming 75% efficiency, this equates to lifting almost 8000 one hundred pound bags of concrete 40 inches (one meter) each hour, eight hours per day, 250 days per year. For the rest of the world that is about 7,200 fifty-kilogram sacks raised one meter each hour. Would you be able or willing to do such work for 30 years in order to modestly raise a family and fund a small retirement? Not if you are human because it would be physically impossible.
So the next time you hear someone suggest that killing a job in the coal-based power industry and replacing it with one in the solar industry will lead to a better world, realize that each job so displaced will come with vastly reduced productivity. And the next time you hear a green advocate suggest that you can do manually what we are currently doing with the “help” of evil electricity, consider your child’s working life spent lifting 8000 one hundred pound sacks every hour for 25 or 30 years. Or until he/she dies trying.
Such is the magical power of the kilowatt-hour.