This is the cost of the panels. The cost of the electricity produced would have fallen pro rata.
This is why coal is finished. This is why the world will move to reduce emissions at the Paris conference in November/December later this year. Not just because global warming is real and terrifying, but because the costs of the alternative are lower than existing power sources, even without a carbon tax/cap-and-trade. With them, solar will sweep away coal.
Disclaimer. After nearly 40 years managing money for some of the largest life offices and investment managers in the world, I think I have something to offer. These days I'm retired, and I can't by law give you advice. While I do make mistakes, I try hard to do my analysis thoroughly, and to make sure my data are correct (old habits die hard!) Also, don't ask me why I called it "Volewica". It's too late, now.
BTW, clicking on most charts will produce the original-sized, i.e., bigger version.