Chevy Volt Charging Math doesn't add up
Posted on Oct 2, 2008 by Paul White
When something sounds too good to be true it usually is. The ChevyVolt has been getting lots of hype. GM's press department has beencareful about what figures to release. Knowing that any numericalfigures would be scrutinized by engineers and techies. Well I workedsome numbers and have come to the conclusion that the Chevy Volt is notwhat it seems.
A few of the facts we know are the Chevy Volt has a 16 KWH battery.
The Chevy Volt is supposed to do 40 miles on the battery, before going into Gasoline mode.
The Gasoline mode kicks in when the battery reaches 30 percent charge remaining.
So from this we can assume the battery never gets below 30 percent.
This means that the 16 KWH battery never has any less than 4.8 KWH remaining.
This means that the Volt is able to go 40 miles on 11.2 KWH
Assuming 100% efficiency which doesn't happen a 11.2KWH battery would take 11.2 KWH to charge.
GM assumes household utility rates of 10 cents / KWH. Meaning it would cost $1.12 to charge it at home.
Of course in Texas and other states, we don't get these cheep rates. Try more like 16 cents / KWH.
This means at the average Texas rate it would cost $1.79 to charge your Volt.
But once again no charger is 100% efficient. There is always lost efficiency due to heat.
A highly efficient charger still only makes 60-70%. We will give the Volt the benefit of the doubt and assume 70% charging efficiency.
This means means the 11.2 KWH you are trying to charge back into your Volt only represents 70% of the power you used to charge it.
In reality you used 14.56 KWH to charge your Volt.
Meaning your cost to charge the car in Texas is closer to $2.32.
One of the claims GM was making was that the cost to drive the Volt was 2 cents / mile.
If that was so then it would only cost 80 Cents to Charge your Volt for the 40 Miles in Electric only mode.
But from what we have found it costs almost 3X this much to fully charge your Volt in Texas.
The Volt is rumored to get 50 MPG in Gasoline Mode. This would be slightly better than a prius.
But considering you can buy a new prius for $22K, and the Volt is rumored to be priced closer to $40K. I don't see how the Volt will ever make it off the ground.UPDATE
I have written an updated article comparing the 2011 Chevy Volt vs 2011 Toyota Prius