All electricity installations are subsidised, one way or another. What we need to ask is what the subsidy is for and if it is likely to help. As far as I see it the question comes down to how much investment it would take so that solar is cheaper than other forms of energy production. If we are in the situation where that is about to happen soon and where a major factor in keeping prices high is economies of scale, then the subsidy is sane and is likely to result in economic benefits that massively outweigh the cost of the subsidy. Otherwise it isn't.
