If you don't want experiments going on around your servers you better host them in your own data center. Amazon is guaranteed to be running many experiments in all of their data centers (and not just with power, with the actual server hardware!).
While that' one way you can look at it, another is that hopefully this region should now be less prone to power outage related downtimes. I wonder if they are an issue currently though.
AWS will be running a 4.8 megawatt hour pilot program with Tesla's batteries in the us-west-1 AZ (Northern California).
Hopefully this allows AWS and other hosting providers to use intermittent, renewable sources of energy more often.
EDIT: I'm guessing AWS will be using a cluster of 48 power packs (100 kilowatt hours each).