For these industry-disruptor things you need some degree of support from the industry you're disrupting (i.e. you need to sell to utility companies that have strong business relationships with the large generation technology providers in the space). In practice this means raising money from, or partnering with, the right people that can leverage industry connections.

It is easier to get the right investors and partners if you are not controlled by Alphabet, because investors and partners have more assurances of the governance leverage they get for their money/effort. If you are Sergey's pet project, you are very vulnerable to mood swings on his (or Google's) behalf.