A lot of people try to guess at true Chinese GDP using Electricity consumption as a proxy. Here is a little review of estimated US energy usage through since 1930. I can't vouch for the source Wattzon or data integrity, but it really makes one think about firms in the peak energy management business like Enernoc (ENOC) or grid pressure relief systems. I wish the graph below were semi-log to more clearly highlight to 1930's decline.
I found the chart in Paul Kedrosky's mention of an energy conference presentation.
Carbon credits, utilities etc. and anyone used to steady state energy consumption growth is probably in for a bit of a shock. Smart metering, behavioral changes and other end point and grid efficiency gains will only exacerbate this shock for energy producers and their respective supply chains, railroads etc.