Opinions on this vary, but it appears that sometime in the next ten years, domestic solar power will have an unsubsidised cost that is below the daytime domestic grid tarrif.
I need to be clear here what I mean by "unsubsidised". I mean that the equipment can be bought and installed without a contribution from either the government or the suppliers(s) of electricity. I'm also assuming that customers will be able to net off their daytime electricity consumption by selling their surplus solar power to the utility at the same price as they'd buy it at that time of day.
There are arguments about whether such a framework is really unsubsidised, but that's the definition I'm using here.
The subject is "what happens when...?"
At that point, rational consumers will install solar power systems. Further, for those that cannot raise the capital, I would envisage business moving in to install and lease the equipment to the consumer, because it will be possible to let the consumer have electricity for less than the grid price while providing a profit to the lessor.
So there should be solar panels on every domestic roof that receives enough sunlight. The grid will only be supplying electrity during the day when the sky is overcast. This affects the economics of the power plant. In particular, I would anticipate a move away from combined cycle (CCGT) natural gas generation to the less capital intensive, and less energy efficient, generation plant.
That less efficient plant will produce more CO2 per kWh than the plant that it replaces, but will produce less energy overall (since the solar panels are producing some). I have to wonder how that pans out. Is the CO2 purportedly saved by having the solar panels actually simply tranferred to the outputs of the less efficient generators?
The cost of this less efficiently generated power is higher than that produced by CCGT. Since that higher cost must be passed on to consumers, it means that the unit cost of grid power during the day will go up, thus further pushing the installation of solar panels.
Of course, that's based on unsubsidised solar panels with a simple net-off of consumption. For some bizarre reason, governments still want to help create the problem earlier than it would otherwise occur by subsidising installation, and forcing retailers to pay more for solar generated power than it's worth to the retailer.
I'm left wondering whether solar power is a mirage. Is it providing any benefit whatsoever? Or is it a complete and utter waste of money, regardless of whether CO2 emissions are a problem?