I want to better understand the energy consumption of electric cars. I’m not even going to discuss the EPA’s MPGe (miles per gallon equivalent) ratings for electric cars. I completely ignore this figure. I will never drive along in my pure electric car thinking… “I’m averaging 95 MPGe on this trip to the beach!” Especially when everything related to the EV will be in kilowatt-hours (kWh). Sizing of the car battery pack is in kWh. I’ll charge the car at home, then pay the electric bill which is based on kWh. Also while driving the car it will show instantaneous watt-hour per mile consumption.
I want to think in electric / energy terms and have a good understanding of relational consumption. The easiest way to understand energy consumption is to relate it to stuff we already understand. Charging a cell phone, a 60 watt light bulb, a 1400 watt coffee maker etc. We all have a pretty good idea of how much power these devices consume. Let’s relate this knowledge to EV’s.
Consider the energy consumption of the following cars. The kWh rating per 100 miles is pretty common to find now. Based on that number we can calculate the Watt-hours per mile:
watt-hour = 1000 × kilowatt × hour
abbreviated: Wh = 1000 × kW × h
We can also calculate Miles Per Kilowatt-hour (MPkWh):
kWh / 100 mi data source: www.fueleconomy.gov
The average watt-hour per mile of these electric cars is 312 Wh/mi. We can now relate that energy consumption against some common household devices:
Showing the math for the Keurig coffee maker for example:
Another fun comparison… how many times would you need to charge your phone to equal the same energy consumption of driving an EV 1 mile??
You would need to fully consume the S7 battery 21.33 times to equal the same energy usage of an electric car going 1 mile.
312 Wh / 14.63 Wh = 21.33