As I evaluate solar technologies and vendors for an installation in my home, I was interested to see the shift in US electricity generation in the first half of the year. It’s hard to believe that just 5 years ago coal had a 40% share in power generation. The relentless cost declines, government subsidies and capacity increases for both wind and solar are now very much a part of coal’s current declines. Combine that with the learning rate of renewables should add further downside pressure on coal, estimated to fall to the low 20-25% with wind and solar picking up the slack for a combined 15% by 2020.

The technological advances have pushed efficiency's into the low 20% making solar installations nearing a 5-6 year ROI. While solar for the home becomes more cost competitive and an increasingly better ROI, you can’t say the same for solar stocks. TAN, the solar ETF is down 90% from its inception date.

For now and until things change most of your eco-friendly investment dollars appear to be best utilized in your home rather than your portfolio.