Spider
What makes you think our future will be low energy?
Current research is looking at thermal solar power, ocean thermal power, ocean wave power, hot rock geothermal, high altitude wind power, thermal tower power, nuclear fusion power, nuclear fission/fusion hybrid power, uranium pebble nuclear fusion power, new forms of tidal power, new generation solar panels, phytoplankton hydrogen generators, algae biodiesel manufacture etc etc.
Even if just a few of these gel, there will be masses of extra power over and beyond what we have today. Ocean wave power alone can supply the world's needs many times over in theory.
Hell, just a breakthrough in nuclear fusion (timed for 2018) will yield so much electricity that energy will never again be a limiting factor.