Around 2016 (more or less) we are going to reach a crossover point, called grid parity. The cost per watt of buying, installing and using a solar system is going to get below the actual cost of buying electricity from the grid, below the cost of generating it with coal or natural gas and transporting it to you.
It’s at this point that I expect open source to shine, because the supply-demand balance will shift. Instead of having to push demand for solar systems, manufacturers will find themselves falling behind demand, just as PC makers began running short (despite production increases) of consumer demand for PCs in the late 1970s, after decades where salesmen had to call on folks to sell mainframes or minicomputers.
When a technology becomes common, when it starts to become standardized, when it has proven itself in the market, that’s when the savings and benefits of open source become obvious.
We’re just getting warmed up.