possible FAQ: how is mpge calculated?

The car nevers does an MPGe calculation. It only does mpg when in HV mode and kwh consumed during EV mode.

To do MPGe you do not use the price but use the energy content...

MPGe = total miles / total energy
You can get from wikipedia.

Mike

 

33.7 KWH = 1 GALLON

 

33.7 KWH = 1 GALLON and PIP kWh = 85% of Kill A Watt meter kWh due to charging loss.

Then wouldn't MPGe = Total Miles /[Pump Gallons + (.85 * Kill A Watt kWh/33.7)] ?
Seems correct.


However, drinnovation, who helped setup the formulas of the MPG Spreadsheet, is using
MPGe = Miles*33.7/(Gallons*33.7+1.15*kWh)

Are the formulas equivalent?


Miles*33.7/(Gallons*33.7+1.15*kWh)
Miles/(Gallons*33.7+1.15*kWh)/33.7
Miles/[(Gallons*33.7)/33.7 + (1.15*kWh)/33.7]
Miles/[Gallons+ (1.15*kWh/33.7)]

DR.Innovation, I need your help !!!

 

MPGe = Miles*33.7/(Gallons*33.7+1.15*kWh) ??

So 500 miles and 10 gallons and 3 kW gets you 49.5 ?? Less than 500/10=50mpg?? Then why plug in?

Personally I think the whole MPGe is bogas.

 

Only plugging in once per tank, as with your example, is basically not plugging in.

Far more realistically is plugging in every night. The result is both higher MPG and higher MPGe.

 

Consider the cost of the relative efficiencies of the two fuels.
In my area gas cost $3.90/gallon & a kWh of electricity cost 12 cents.
33.7 kWH = 1 gallon of gas
To account for charging inefficiency 33.7 kWh x 1.15= 40.7 kWh
Cost of gallon equivalent kWh from wall plug $4.88

Consider the relative efficiency of the two fuels
PIP
Gas 41.5 miles using 10 gallons
41.5 mpg

Electric 912 miles using 265 kWh
Account for 15% charging inefficiency 304.8 kWh (300 x 1.15)
Convert to gallon equivalent 304.8/33.7 = 9
MPGe = 912/9 = 101.33
It takes 2.44 gallons of gas to drive 101.33 miles at a cost of $9.51

Cost per 100 miles
Gas $9.4/100 miles
KWh $4.82/100 miles

 

Breaking out cost like that doesn't work with a plug-in hybrid, since there's so much blending... which complicates the understanding of MPGe.

Here's my real-world data:

17,194 miles

221.7 gallons

1,578.3 kWh (including charging loss)

(((221.7*3.9)+(1578.3*0.12))/17194)*100 = $6.13 / 100 miles

That's overall, of course, which doesen't necessarily reflect what was actually paid. It just gives an idea of the efficiency itself.

 

You are correct! However given JamesBurke's comment my goal was to demonstrate the relative cost/efficiency advantages of using kWh as opposed to gas.