Energy efficiency is now the 3rd largest electricity resource in the US and also the lowest cost way to meet customer's needs. The graph below, with data from the American Council for an Energy-Efficient Economy (ACEEE) and Lazard, shows how energy efficiency has the lowest cost per kiloWatt hour of any energy resource. Traditional electricity sources like fossil fuels have 2-3 times the cost of efficiency.
Many facility managers and building owners invest in energy efficiency for the money they will save, but the ancillary benefits are myriad and include curbing climate change and reducing carbon emissions. While US energy consumers as a whole have saved nearly $790 billion since 1990, they have also avoided building the equivalent of 313 large power plants because of energy efficiency. The environmental impact of avoiding building these power plants is not easily quantifiable, but has surely been positive.
Energy efficiency is currently even cheaper than renewable energy sources but as those technologies scale the hope is that they too become as cost effective. Once efficiency and renewables can be used in concert at a cost effective price, they will be adopted on a widespread level and real change can occur on a global scale.