EV v. Hybrid: Calculating the Energy Cost of Your Daily Commute

[Doc Rock]

Here's a fairly simple method I use to calculate the energy cost tradeoff between running in EV Now and EV Later modes for my daily commute.

 

First, I note the kWh used for daily R/T in EV Now mode. The R/T is 9 miles (4.3 miles to/4.7 miles from - I use a different route coming home due to traffic). I use about 2 kWh per R/T.

 

Second, I note the amount of gas I use on the same 9 mile commute in EV Later mode. I get about 45 MPG for the R/T on average. That's about 0.2 gallons for the 9 mile R/T.

 

So, on a weekly (5-day) basis, I would use 10kWh in EV Now mode, or, 1 gallon of gas in EV Later mode.

 

Electricity costs me just at $0.12 per kWh. Gas costs me about $2.20 per gallon (I'm in PA, home to the nation's highest gas tax!)..

 

So, in EV Now mode, the weekly energy cost for my commute is $1.20. My gas cost is $2.20 in EV Later mode.

 

The tradeoff is likely to be less favorable as cold weather approaches, but right now, I'm plugged in!

[murphy]

My electricity costs me $0.006 per kWh.  Guess which mode I drive in?

 

[i have 10 kW of solar panels on the roof of my house].

[bdginmo]

Remember that you'll pull more kWH from the wall than what the trip computer says. This multiplier is about 1.38 and 1.22 for 120v and 240v charging respectively. I've also noticed a phantom loss not accounted for by the car's display. As the battery temperature changes with the car off the remaining SoC may be lower the next time you turn it on. Doing some experiments I have calculated this effect to be about 0.1 kWH per discharge for me during the warm season. Taking these into account you probably pulled more like 14 kWH from your meter. You still come out ahead using EV. Do your electric rates go down in non-summer months? Mine is $0.1225 in the summer and $0.0590 in the fall, winter, and spring.

[Doc Rock]

Remember that you'll pull more kWH from the wall than what the trip computer says. This multiplier is about 1.38 and 1.22 for 120v and 240v charging respectively. I've also noticed a phantom loss not accounted for by the car's display. As the battery temperature changes with the car off the remaining SoC may be lower the next time you turn it on. Doing some experiments I have calculated this effect to be about 0.1 kWH per discharge for me during the warm season. Taking these into account you probably pulled more like 14 kWH from your meter. You still come out ahead using EV. Do your electric rates go down in non-summer months? Mine is $0.1225 in the summer and $0.0590 in the fall, winter, and spring.

I  purchased a P3 Kill a Watt to monitor actual kWh flow into the battery. Yes, it is higher than the onboard computer indicates - roughly 20-25% higher at 120V. Still, I'm at about 3.4 cents per mile in EV. Not likely to be that low as the weather turns colder.