McKinsey has published a good summary of the options for improving our energy efficiency that exist (already) for homes, commercial, and industrial settings: US Energy Savings: Opportunities and Challenges.
Essentially they divide homes, commercial and industrial settings between infrastructure and process demands (in homes, it's shell and HVAC versus devices and lighting) and consider the capital investment required and the net present value of the savings from EE investments in each of these areas.
The article also does a nice job pointing out some some of the barriers associated with EE retrofits and improvements. They don't address the principal/agent problem (someone creates the energy demand, someone else pays for it) but otherwise capture many of the key barriers.
Of particular note is that, while energy efficiency improvements are the most cost-effective, technologically mature, and easiest to scale of our options, they also address the most fragmented and embedded of our markets. The solutions all require coordinated efforts between researchers, entrepreneurs, investors, and policy makers.
These are not problems that will be solved by two guys in a garage, jet-setting venture capitalists, or federal policy makers acting alone. Much of the coordinated effort will have to happen at the local and state levels—in the forms of financing, utility initiatives, business incentives, and building codes and standards.