13 miles certainly doesn't get you very far, yes. And even during those 13 miles the engine isn't completely off all the time.
However, if you tend to make a lot of short trips at low speed, the engine would be off almost all of that time. Short trips are very desirable to target, however, because tend to really drop your mileage. That, since gasoline engines run especially inefficiently at low speeds, or at idle. Or before/while warming up.
On a somewhat-related note, I've seen discussions of the Volt of the nature of, "I wouldn't buy this thing because, I can't fit my 50-mile commute into the nominal 40 mile pure-electric range of the car." Well, OK, but isn't burning 10 miles of gas a big improvement over burning 50 miles worth of gas?
As distances here are expanded compared to other parts of the country, <13 miles doesn't get us very far. I didn't mention in my post that I sold the Prius 2002 because it had no trunk. My needs changed, so I bought a used 2002 Aerio SX (Suzuki) hatchback (in 2004) that has good carrying capacity. Put $7k in the bank. It gets a measured 29-30 mpg, losing 1 mpg when the A/C is on.
Air conditioning certainly does take a bit out of my 2009 Prius' mileage, but thankfully not to the point of keeping the engine running all the time. Then again, here in Austin, it's only 100 degrees at 9:30PM! :-)
Rob: Automakers are definitely considering battery replacement, and are trying to make it part of the buying decision. GM offers an eight-year, 100,000-mile warranty on the Volt's battery. The fact that they did so indicates consumers are asking about it. However, my guess is that most consumers aren't asking about it until it comes time to plunk down the money. Nissan actually interviews prospective buyers of the Leaf to make sure they understand the issues associated with the performance and care of an electric car.
I think that full-production EVs are still new enough that a mentality related to battery replacement has not yet to emerge. However, I think the expectation is that you simply won't need to replace traction batteries for a normal expected lifetime of the vehicle - say, 150Kmiles. As for whether it will really happen that way ... I guess we'll see.
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