let me start by saying two things:
a) I am very very excited to received my Tesla Model S
b) despite the questions below - I have placed my own money on this car…
Question and thoughts center around the longevity of the battery (a question no one can answer) and cost of replacement
1. we know the cost to replace an 85 kwh battery is ~$12,000
2. we know the warranty is 8 years/unlimited mileage
3. we know batteries maximum charge degrade over time
4. eventually it will be worth while to replace the battery to get back to the vehicle's original capabilities
therefore I believe we have the consider the cost of the battery replacement in the annual cost to "fuel" the vehicle and if you do this the cost to run the car per-mile vs. an ICE car by tesla's own numbers is not very favorable
Assumptions: 15,000 miles year, ICE 22 MPG, gas = $3.80 gallon, kwh's = $0.11/kwh
by Tesla's own numbers @ http://www.teslamotors.com/goelectric#savings
ICE Car = $2591 year in fuel cost $0.17 per-mile in fuel
Model S = $467 year in fuel cost $0.03 per-mile in fuel
that is until you figure in the cost of replacing the fuel tank at the end of an 8 year life span (the battery) - for which you have to budget $1500 year - making the cost of the Tesla's fuel system $1967/year or $0.13 per-mile in fuel…
now I know there are other costs the ICE car has - but for purposes of this thought exercise let's focus on the "fuel" system cost and treat the battery as the moral equivalent of the "fuel tank". Which in an ICE car doesn't shrink, or need to be replaced in 8 years.
Even a 16 year replacement is $750/year in "fuel" cost to the battery…that still seems to be far less of an advantage than most people would initially consider?
Are there estimates of what the maximum charge of an 85 kwh battery will be in 8 years? What % a year will we as customer lose? How much will my fuel tank shrink each year?
I'm thinking I would replace the battery after it loses 20-25% (300 miles - 75 miles of loss = 225 miles of range - time to swap batteries) of it's maximum range, and if that happens in less than 8 years my fuel-system costs now approach the cost of driving an ICE vehicle…
I'm still excited to get my car, and I'm committed to the success of EV's - but I'm still having trouble with the actual economic benefits when the total life cycle cost is considered - in this case the full costs given the battery replacement cost amortized into the car seem to dramatically change the cost curves.
thoughts, comments, if it takes 20 years to lose 10% capacity then we're good, however if it's more like 20% in 6 years I think the battery cost make the car more expensive to drive.