I like the domain, with that many people using that much energy, it not surprising they have been pushing Solar a lot lately
I would hold onto it for another 2/3 years and wait until Solar Power is a major player and then you will have a few more end-users to target, there are plenty now if you're in a rush, but my advice is hold onto it.
You only have to read some of these articles to see the potential in the name. AS you can see by my signature, I may be a little biased. Good luck though