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:: Fun With Miles per kWh

Ok, so yeah, a bit of a follow-up on the electric vehicle front

In short, i got one. Well, sort of.

What i got was a Plug-in Electric Vehicle, which gets about 48* mpg city and a pure electric range of about 26** miles. Since that’s twice what the last car got, and my work (which is 10 miles away) very kindly provides free charging, i expect my fuel bill to drop a fair bit. The car is also pretty fun to drive and ticks pretty much all my required checkboxes (aside from a trailer hitch for a bike rack, but that’s something i can solve pretty easily).

What’s really interesting is doing the math on the charging bit, and why i’m now super happy with a PHEV rather than a full on electric. Particularly since i’m a right cheap bastard at times.

Consider, as stated, my car now gets about 26 miles on 8.6 kWh, or about 3.02 miles per kWh. That’s the max range on the full battery in pure electric mode, probably with a strong wind at your back and ample down hills, but good enough for now. It takes 2 hours and 42 minutes to charge up from pretty much zero on a Level 2 charger.

The hybrid engine gets me around 48 mpg in the city, which is what i generally drive. Again, presume strong winds, ample down hills, and whatever other bits gets you to that high of a number.

Currently, gas goes for around $3.30 per gallon. 26 is about 54% of 48, so it’s safe to assume that running pure electric is equivalent to running about half a gallon of fuel. That means it costs me $1.15 to drive the equivalent distance if my battery is flat and i use the gas engine.

So, when i charge, i want to look for any charging station that costs less than $1.81 total to use. That means anything that’s $.01 a minute (well, $.68 per hour because rounding) or less, or charges less than $0.21 a kWh. According to PG&E, my power company, i pay $0.28 per kWh peak (between 1:00 PM and 7:00 PM) and $0.27 off-peak, so it doesn’t really make sense to charge at home. i’d be paying an equivalent $4.64 for a gallon of gas.

What floors me is that looking at various commercial charging sites charge even more. EVgo, charges $1.50 an hour, which is like spending $6.70 a gallon on gas. i mean, i totally understand companies needing to make a profit and all, but Holy Ampère that’s a lot. Granted, it gets worse. There’s at least one “public” charge station nearby that charges $4 an hour. That’s about $11 a gallon.

i’m going to guess that my car is probably less efficient a pure EV than, well, a pure EV, but even so, if you’ve got an 80kWh battery and your range is 300 miles, that gets you about 3.75 miles per kWh. Still, a full “tank” of electricity still costs far less than it used to in my last car, so not really complaining. i’m also willing to bet that prices per kWh are probably less outside of the Bay Area, but yeah, i’m fine plugging into the free stations when i can and may just skip the pay ones.

Sam Penrose wrote up his thoughts about gas stations vs. electric. i’ll note that in the summer months, i’m getting around 51 MPG, and can fully charge off of the solar panels while they’re producing > 3kWh, and still send some to the grid. i’ll also note that the car is a blast to drive as pure electric, so i tend to charge up frequently.

* for the pedantic, after about a week, i’m seeing around 42mpg and the full battery charge gets me around **24 miles, but it’s also winter, which sets my target price per kWh to $.24 or $.77 an hour.

Blogs of note
personal Christopher Conlin USMC memoirs of hydrogen guy rhapsodic.org Henriette's Herbal Blog
geek ultramookie

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