View Single Post
Old 11-10-2010, 11:30 PM   #32 (permalink)
RobertSmalls
Left Lane Ecodriver
 
RobertSmalls's Avatar
 
Join Date: Aug 2008
Location: Buffalo, NY, USA
Posts: 2,257

Prius C - '12 Toyota Prius C
Thanks: 79
Thanked 287 Times in 200 Posts
Quote:
Originally Posted by 04_Sentra View Post
Personally, I don't like any of the methods of calculating mpge.

Life Cycle Energy Equivalence - Unfairly compared Well to Wheels for EV to Tank to Wheels for ICE.
CO2 Equivalence - Makes an assumption on where I get my electricity and it's CO2 content.
Cost Equivalence - Makes an assumption on how much I pay for electricity.
Direct BTU Equivalence - Gives unrealistic expectations on the range and cost of operation for EVs.

What I need to know is capacity of battery pack in kWh, and "fuel economy" in wh/mi, and I can figure the rest out.
I don't like the term "mpge", because wh/mi can not be made equivalent to mpg. Certainly not universally. Still, you can do a weighted average of the above methods, tailored to your specific situation and values. You can also make some reasonable assumptions about people's values, and you'll come up with a figure that's about half of the direct BTU mpge figure.

Let me stand up for the first two methods.

Life cycle energy equivalence: I have presented well-to-wheels data for gasoline (not tank-to-wheels), and well-to-plug data for electric, so you must measure power consumed by the charger, not by the inverter as reported on the dashboard.
CO2 equivalence: Considering that electricity is fungible, and we're all on the same grid, grid average figures are appropriate for estimating the impact of mass adoption of EV's.
  Reply With Quote