It’s Halloween, and if you are like me, that means you are about to eat several pounds of candy corn, nibbling off the colored stripes one at a time as if dissection could forestall the inevitable nausea. But real candy corn aficionados know that nausea is something you can power through: There’s more candy corn out there, hurtling toward staleness and in need of a welcome belly.
I’ll admit, my fervor for a candy many people consider repulsive may be irrational. So this year, I decided to channel my obsession into something useful – or at least something entertaining. So, I asked:
How many pieces of candy corn would it take to charge a cell phone for a day’s use?
To be clear, the technology does not yet exist to plug your phone directly into a bag of candy corn. But energy comes in many forms – caloric energy in food, chemical energy in gasoline, electric energy delivered via the grid, kinetic energy in flowing water – and it is possible to compare them  to gain a better understanding of how we use energy.
So, let’s start by looking at how much energy is in a single piece of candy corn in the form of calories, which are actually kilocalories (kcals)  in energy terms.
A serving of 19 pieces has 140 kcal, so a single piece of candy corn is about 7.4 kcal.
Next, we need to know how much energy – in the form of electricity – your phone uses in a single day. Let’s assume that you charge your phone once a day, and you are giving it a full charge – the battery starts off drained and ends up completely full. It takes somewhere in the range of five to 13 watt-hours to charge a smartphone. This varies depending on the type of phone and how old the battery is, but for simplicity’s sake let’s use an estimate of 10 watt-hours.
Finally, we need to convert our candy corn energy into watt-hours in order to compare the two. One kcal equals 1.16 watt-hours, so one piece of candy corn is equivalent to about 8.6 watt-hours. Which means…
Your phone’s battery holds roughly the same amount of energy as a single piece of candy corn.
Of course, this is only a thought experiment. You can’t actually chew up a mouthful of candy corn and spit it into your phone’s charging port – well, you can, but it will only make your phone stickier, not more charged.
But this trivia question isn’t trivial: It reveals just how little energy a phone uses, and how much energy sugar holds. That giant pile of candy corn I’m about to snarf, maybe it could do more than make me sick and happy. Which makes some seemingly wacky ideas – like Steven Chu’s glucose economy – sound, all of a sudden, not so far-fetched.
And it helps us put our energy use into perspective. Contrast a cell phone’s candy corn equivalent with how much it would take to boil a cup of water  – about 2.5 pieces. Or compare it to a gallon of gas  – about 4,000 pieces (or 20 pounds, enough that even a candy-corn freak like myself might have trouble eating).
Because they are both day-to-day activities, we often put driving our cars and using our phones in the same mental category. But our daily energy use spans orders of magnitudes, as do the challenges, technologies, and policies involved in our ever-evolving energy economy.
 If you were to actually convert a piece of candy corn into electricity, you would lose some energy during the process because it wouldn’t be one-hundred percent efficient.
 What we colloquially call a calorie in the U.S. is actually a kilocal, which is the amount of energy it takes to raise one liter of water by one degree Celsius, at sea level.
 It takes 79 kcal to raise a liter of water from room temperature (21 degrees Celsius) to boiling (100 degrees Celsius). One cup is 0.235 liters, so it needs 18.6 kcal. A piece of candy corn is 7.4 kcal, so that works out to 2.5 pieces.
 A gallon of gas contains roughly 33.7 kilowatt-hours of energy, or 33,700 watt-hours. A piece of candy corn has roughly 8.6 watt-hours, which means a gallon of gas has roughly the same amount of energy as 3,919 pieces of candy corn.