Google's approach subsidizes the additional cost of renewable energy sources over fossil fuels. Because Google sells exactly what they consume, they aren't actually inducing more electricity demand. And even if that was a factor, renewables are still an order of magnitude more green than coal.[1] So feel free to invest in solar companies :-)
By the way, carbon neutrality is easier to achieve than 100% renewable. Google has been carbon neutral since 2007,[2] which means that they purchase carbon offsets for their carbon usage. Carbon offsets are cheaper than renewable energy credits because there is lower-hanging fruit. For example, agreeing not to clear-cut a forest for 20 years generates millions of tons of carbon credits.
[1] https://en.wikipedia.org/wiki/Life-cycle_greenhouse-gas_emis...
[2] https://googleblog.blogspot.com/2007/06/carbon-neutrality-by...
