Stock Market Compound Annual Growth Rate (Annualized Return) of 6% to 7%

Please check out this site:  http://www.moneychimp.com/features/market_cagr.htm

The take away:  "Over the very long run, the stock market has had an inflation-adjusted annualized return rate of between six and seven percent."

Investing in your own solar electric system will usually meet or beat the stock market.  Now you can be rest assured knowing your investment is right next to you and not in a black hole somewhere subject to the volatile emotions of others.