The reason I am using this metric is because of the statement Nissan made on page EV-3 of the 2011 LEAF Owner's Manual:
I've been thinking about this question quite a bit lately as our LEAF has gone through the coldest winter that we have seen in a LONG time, yet it has steady lost capacity with very little driving. At this point we have about 58 Ah capacity remaining, which is about 87.5% of the original 66.25 Ah. We have owned our LEAF for about two years now, but it is a demo with 2.5 years gone from the warranty.2011 LEAF Owner's Manual page EV-3 wrote:NISSAN estimates that battery capacity will be approximately 80% of original capacity after five years, although this is only an estimate, and this percentage may vary (and could be significantly lower) depending on individual vehicle and Li-ion battery usage.
I am one who believes that calendar losses on the LEAF are closer to linear than logarithmic, so I expect our battery capacity to drop below the 80% mark well before five years are up. The question I have is if even low-mileage LEAFs found in cold climates will achieve the level that Nissan officially estimated in our Owner's Manuals.