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#1
04-22-2012, 09:56 PM
 Ziggythewiz Senior Member Join Date: May 2010 Location: Houston Posts: 3,721
200 MPGe

Over the last year of driving I've seen my wh/mile (from the wall) increase significantly. It started at a consistent 250 and is now up around 333. I attribute this to aging/replacing batteries and unidentified mechanical issues.

At the same time, my charging cost has dropped significantly so I did some refiguring on my MPGe.

There are at least 2 ways to calculate MPGe:

Method 1 is more textbook and less variable, using the EPA energy
equivalency of 1 gallon = 33.7 kWh, so 33.7 / Wh/mile = MPGe

Method 2 is much more variable, but also much more relevant and uses your actual cost/mile compared to the cost of a gallon of gas, so \$/mile * your alternative gas price = MPGe

A year ago both methods were about the same at ~135 MPGe

Now method 1 gives me ~100 MPGe and method 2 gives me ~200 MPGe
__________________
1 EV - 8,530 e-miles in 2 years (2/11/13) - http://www.evalbum.com/4000

Last edited by Ziggythewiz; 04-23-2012 at 10:15 AM. Reason: Bad memory
#2
04-23-2012, 09:28 AM
 tomofreno Senior Member Join Date: Mar 2009 Posts: 1,940
Re: 200 MPGe

Quote:
 Originally Posted by Ziggythewiz Over the last year of driving I've seen my wh/mile (from the wall) increase significantly. It started at a consistent 250 and is now up around 333. I attribute this to aging/replacing batteries and unidentified mechanical issues. At the same time, my charging cost has dropped significantly so I did some refiguring on my MPGe. There are at least 2 ways to calculate MPGe: Method 1 is more textbook and less variable, using the EPA energy equivalency of 1 gallon = 33.7 kWh, so 33.7 / Wh/mile = MPGe Method 2 is much more variable, but also much more relevant and uses your actual cost/mile compared to the cost of a gallon of gas, so \$/mile * your alternative gas price = MPGe A year ago both methods were about the same at ~160 MPGe Now method 1 gives me ~100 MPGe and method 2 gives me ~200 MPGe
Not following you here, 0.250kWh/mile is 33.7/0.25 = 134 MPGe, not 160. What changed to now get 100 MPGe, or 0.337kWh/mile?
#3
04-23-2012, 10:14 AM
 Ziggythewiz Senior Member Join Date: May 2010 Location: Houston Posts: 3,721
Re: 200 MPGe

You're right. The old numbers were around 135 (gas was \$3.40 then with electric around \$0.10 so \$3.40/.025 = 136), I guess a later calc via method 2 put it around 160 and that one stuck in my head.

Anyways, my efficiency has gone down, lowering my method 1 MPGe, but gasoline going up 15% and electricity going down 30% has raised my method 2 to ~200 MPGe.

Progress! Now if I could just get that wh/m back down to 250...
__________________
1 EV - 8,530 e-miles in 2 years (2/11/13) - http://www.evalbum.com/4000

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