It appears that Zero offers a capacity retention guarantee on their power packs. This is actually one of the more generous warranties of its kind; Nissan is the only other EV manufacturer that I'm aware of that offers a similar protection, and their warranty protects against a
30% reduction.
Zero will only repair or replace pursuant to this Limited Warranty a Power Pack that exhibits a nominal storage capacity reduction of greater than 20% of the published nominal capacity, as measured by an authorized Zero dealer. To check the capacity of a Power Pack, an authorized Zero dealer can perform a battery management system log data extraction, which will confirm if a reduction is within expected norms.
This capacity warranty has been
available since the 2014 models, which I previously missed.
New for the 2016 bikes, both the 2 year limited warranty and the 5 year power pack warranty have been extended by
90 days, to 2 years and 90 days and 5 years and 90 days respectively.
Warranty information is available in the owner manuals, available for model years 2010-2016 at Zero's site.
http://www.zeromotorcycles.com/owner-resources/