Diana Ferrel, the director of the McKinsey Global Institute, is currently making a convincing case for energy efficiency at the UN Investor Summit on Climate Change (the FT has a good summary). The world is obsessed with supply-side solutions to climate change (alternative utilities, renewable fuels, etc.), but demand-side solutions (i.e. increasing energy productivity) could offer remarkable results at, according to Ferrel, a profit. An investment of $194 billion a year (using ideas such as those detailed here) could yield a $17 billion a year profit, as well as getting us halfway to the reduction in carbon emissions that we need. We’re talking about a possible reduction in oil consumption of 64 million barrels a day. As Ferrel puts it, even if you plus up the use of solar energy by 500 percent or wind energy by 1000 percent, you get less savings in carbon emissions than those McKinsey suggests.