In a excellent piece this week, Joe Romm reiterated why battery changing stations don’t make sense for electric cars. But he also argued that plug-in electric ranges of more than 20 miles do not make sense because cost gets too high for too little benefit. This seems a reasonable deduction from high (and rising) costs for the Chevy Volt. But this is a case where the efficiency could be cheaper than conservation.

Consuming 0.4 kWh per mile electricity usage, the Volt currently uses a $10,000 16 kWh battery capacity for a 40-mile range. But lots of electric cars get better mileage than that. For example, the Triac only consumes about 0.23 kWh per mile. Admitting this is fairly extreme, there is no reason a car that needs less than half the battery range (and thus does not need to carry as much battery weight) can’t keep its power consumption around 0.27 kWh per mile, which would make battery capacity 11 kWh rather than 16 kWh.

Beyond this, Chevy appears to be paying too much per kWh for battery packs. Reports in the press say the cost of Tesla motors 53-kWh battery pack is around $20,000. Tesla says the current cost of a replacement packs would be about $30,000, and given markups for such things, this suggests the $20,000 figure is not too far off. But even at the retail figure for Tesla, Chevy is paying $625 per kWh vs. $566 per kWh for the Tesla battery-pack cost. Thus the high cost for the Volt battery pack with a 40-mile range should be about $6,100. If the lower cost was right, the total Volt battery-pack cost would be more like $4,100. That means efficiency, and better battery choices, could save Chevy between 80-120 percent by halving the range before the gas tank kicked in.

In short, the high cost of the Volt is not due so much to high battery costs as using batteries inefficiently and then overpaying per unit of capacity. (I would add that using power more efficiently would save additional money by cutting the cost of the electric motor/inverter combination. Requiring less fuel to recharge the car battery when the electricity was exhausted would reduce the size of the fuel tank and the amount of backup fuel the Volt had to drag around.)