Sunday, August 30, 2009

Is The Chevy Volt Headed For The Trough of Disillusionment?


GM is planning to release the Chevy Volt in November 2010. Put simply, the Volt is a battery electric car with a built in generator. It can drive up to 40 miles per charge on just the batteries and then the generator kicks in. Like a conventional gas car, you can drive until the tank is empty and you can refill at any gas station and keep going as far as you like. Unlike a conventional car though, you can also plug it in, charge it up and then start driving from battery power again.


Did you catch the subtle wording above? The Volt can travel "up to" 40 miles. There is no guarantee that you get 40 miles out of that full charge. However, the "your mileage may vary" disclaimer is blatantly missing from press releases and other media. In fact, if you comb the mass o' videos and articles about the Volt, even the "up to" bit is often not present or only stated the first time. How far can you actually expect to really drive in electric mode? Who knows, that is not what GM is talking about.

GM recently kicked off the "230" marketing campaign. They claimed the vehicle would rate at 230 miles per gallon. That would be great, but it takes some creative accounting to get there. In electric mode, the EPA rated the Volt at 4 miles per kilowatt-hour. Using this number with the Automotive X Prize conversion to miles per gallon equivalent energy (MPGe) and the vehicle rates at just under 150 MPGe in all electric mode. Note that no actual gasoline is being used; this is just a measure of the energy spent. Then when the Volt turns on the generator, it does use gasoline with each mile. This is called Charge Sustaining Mode (CSM). When GM announced the Volt in 2007, they estimated that it would rate approximately 50 MPG in city CSM operation. GM has not updated this number for the actual production vehicle, so we'll use this estimate.

Using these two values, you can see that with short trips in the electric mode you can about 150 MPGe and as you continue past the battery range, the generator kicks in and the efficiency drops to 50 MPG. This means that all trips will fall between 50 to 150 MPGe. A 50 mile trip would be about 105 MPGe and a 200 mile trip would be about 55 MPGe.

Undaunted by this reality, the 230 flag was waved high. GM had a media event, did press releases, appeared on CNN Money and other TV shows to promote 230. But is this hype the right thing for them to do? I want the Volt to be a highly successful vehicle. It greatly reduces oil use and the associated pollution. This is good for national security and the air we breathe, but is building up the hype around the Volt only guaranteeing that it will be a disappointment?

Below is a graph of the Gartner Hype Cycle. This curve applies to many new technologies and the Extended Range Electric Vehicle certainly qualifies as new tech. The graph shows how a product can become highly anticipated and then not deliver on the wild expectations.


Note that these wild expectations don't even need to be from the company in question. The expectation could be set by the media or word-of-mouth. GM is saying 40 miles all electric and 230 MPG, there is a large portion of the population that are going to take this at face-value and expect it when this car hits the streets.

In hope of setting realistic expectations, here is a reality check, my attempt to cut through the hype.

1) The electric range will be less than 40 miles most of the time. And definitely less than 40 miles if:
  • you have a lead foot - fast acceleration eats watt-hours
  • your 40 miles includes highway driving - in other EVs, freeway-speed driving decreases the range by about 20%
  • there will be some degradation as the batteries age - 80% capacity after 10 years would not surprise me
2) The gasoline mode (CSM) the fuel efficiency will be about 50 MPG. The official CSM MPG has not yet been published, you can expect highway to be lower than city. If you plan to drive the car 200 miles between overnight charges, you will only get about 55 MPGe. That is not bad (unless you expected 230 MPG).

Remember there are lies, damned lies, and statistics. The 230 number might have appeared in one obscure corner of an engineer's spreadsheet, but that does not mean it is what you will really get in daily driving. Much of the media and blogosphere called shenanigans on GM's 230 MPG claims. GM might think this was unfriendly media, but perhaps it has been the best thing that could happen.

More than ever, how you drive will greatly impact your consumption. You can get from 50 to 150 MPGe, still sounds like a marketable (hype reduced) car to me. Throw in foreign oil reduction and you have a car that can appeal to both flag wavers and tree huggers.


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