To complete our dive into toasters, let’s look at how much energy it takes to toast your piece of bread. As we discussed yesterday, once you press down the toast lever, electrons are moving in the toaster heating wires. The wire material and the length of the wire determine how much resistance there is to this movement of electrons. When the electrons flow through the resistance of these toaster wires, heat is generated and your bread starts to toast.
The heat that is generated by the toaster wires is measured in terms of power. You may have heard of Watts (W) which is a unit of power. Most toasters in the US are between 750 and 1500 W. This designates how much energy the toaster uses per unit time.
When you press down your toaster lever, the toaster starts a timer based on which “toast shade” you selected (how dark you want your toast). For example, if you selected shade 4, it might mean your toaster operates for 2 minutes and then pops up your toast by releasing the electromagnet holding your lever down. As a side note, toaster manufacturers test out how long it should take for the toaster to produce shade 4 on a typical piece of white bread and then set the timer accordingly.
Toasters are easy to calculate how much energy is used because the entire time the toaster is operating, electrons are flowing in the toaster wires and generating heat. This means the toaster is always operating at full power for the length of the toast cycle.
Bear with me for a minute on the math… Let’s say you run your 750 W toaster 4 days a week and like to use shade 4 (2 minutes). Over the course of a year, that’s a total of 208 toast cycles and 6.93 hours (8min per week x 52weeks / 60min per hour = 6.93 hours/year). Converting that annual usage to kilowatt hours (kwh), which is what you see on your energy bill, equates to: 750 W x 6.93 hours / 1000 = 5.2 kwh
If we visit the EPA website (https://www.epa.gov/energy/greenhouse-gas-equivalencies-calculator), we can check the conversion between kwh and tons of carbon. Using your toaster this way for one year to make 416 individual slices of toast (208 cycles x 2 slices per cycle) equates to 0.004 metric tons of carbon. Some example equivalents to are 9.1 miles driven by average passenger car (22 mpg) or 469 smartphone charges.
Hopefully you found this mini series informative, not just about toasters but also about energy usage and how electricity works to power the things in our homes.