Wednesday, May 6, 2015

Spark EV miles per gallon

This table quickly shows how Spark EV is doing with respect to gas car's MPG. Rows are $/gallon, columns are $/kWh. Reds are less than 50 MPGe; Prius will be better. Yellows are less than 75 MPGe; one can get this with 2001 Honda Insight. Stay in the clear, and no gas car can match the efficiency. The last column is $0.59/kWh, the rate charged by Blink for their DC fast charging.

Spark EV gets 4 miles per kWh of electricity. This figure is actual use including charger efficiency (~80%) after taking measurements, not the inflated number reported by the car. Details of this number and efficiency will be discussed in another blog. The table is based on 4 miles per kWh.

All values are linear, so to convert for less efficient (ie, old battery, different car, you're always driving uphill to get to Mars), simply scale the number. For example, if the car is getting 2 miles/kWh at $3.50/gal and $0.17/kWh, you'd be getting 82.4 MPGe *2/4 = 41.2 MPGe.

You can also do what-if scenarios. When the gas was $2.80 in CA Dec. 2014, I would've been only getting 65.9 MPGe at $0.17/kWh. This is probably worse than 2001 Honda Insight. But if this was early 2014 at $4.00/gal and $0.14/kWh, I would've been getting 115 MPGe. If you live in low tax state, you're probably wondering why CA gas is almost 2 times higher compared to your state. Yes, CA gas prices are out of whack, and that makes Spark EV better than Prius. Welcome to the republic; now hand over your money. I'll discuss this in another blog.

For those of you outside of US who envy operating the Chevy Spark EV, below table shows $/liter, $/kWh, liters / 100 km. USD must be converted to your country's currency by multiplying the correction. For Korea, it's approximately $1=W1000. For Japan, it's approximately $1=Y100. For China, it's about $1=RMB6. For Euro, it's more dynamic, so it's not so easy.

For example, if you're in Korea with electric rate W190/kWh and W1600/liter, look up $0.19 column and $1.60 row to get 1.8 liters/100km.

You can use the online calculator to convert to MPG, but rough estimate is 4 liters per 1 gallon and 100 km per 60 miles. To illustrate using above Korea example,

1.8L/100km / 4L/gal / 60mi/100km = 0.0075 gal/mile
= 133.33 MPGe

To verify that this value is correct, convert $/L to $/gallon and check against MPGe table.

$1.60/L * 4L/gal = $6.40/gal

MPGe table does not go to $6.40/gal. But we can use $3.20/gal and double the MPGe found. At $0.19/kWh, it shows 67.4 MPGe. Twice that is 134.8, pretty close to 133.33 MPGe from L/100km table. Much of Asia and Europe where gas prices are as such, no gas car comes even close to the efficiency of Chevy Spark EV.

No comments:

Post a Comment