I intend to keep, so I only compared cash flow. If you intend to replace the car, I suspect lease is better for 2-yrs (by about $1000) but purchasing is better for 3 yrs (by $2000).
For SF local driving, we only need about 30 miles range, even on weekends. So even if the Leaf's range drop to 60% (in 10 years? 15 years?), we are perfectly fine. What I meant is, technology will advance, and range will increase in future models. But it won't make any difference to us in our driving.
I don't think battery degrading will change the cost per mile. It changes range, but 1kwh is still 1kwh.
Our PGE electric bill is very high, already in tier 3. Actually, changing to E-9A will save us about 40 dollars monthly. (I did my calculation based on PGE bill and usage pattern during the day) The parking garage my wife uses for work has free charging, at least until end of 2013. So, the energy cost for us is negative for this year.
Someone had some info on E-EV in another post. Off peak rate is abou 10 cents per kwh. My calculation shows our home bill will be even lower than E9 without considering charging. If the parking garage no longer offers free charging and we have to charge at home, at 4 miles per kwh, that's about 3 cents/mile cost. .
(By the way, the Leaf replaces an SUV with 15 local mpg, close to 28 cents/mile fuel cost.)
That translates to $210/year EV energy cost. Again, future EV may have better emileage. But even if it improves another 50%, it will only save another 70 dollars per year, maybe 100 max.
So, despite the potential advances in EV tech, it is not a significant factor in lease-vs-buy decision for us.