Here is an article that suggests that 20% of the cost of electricity comes from operating peakers 100 hours per year i.e. about 1% of the time. In other words, peakers are at about 6X the price of regular power. Those who oppose renewables often point to the high cost of storage and compare it to baseload power. However the proper comparison is to peaking power plants. This is true particularly for power markets such as Texas where the storage would be utilized to ride through intermittent cloudiness during the day and during the overlap times when the sun is going down but wind has not yet picked up.
It should be pointed out that Texas has sufficient renewable potential that it could power the country on an energy basis. And as they build power lines out to their highest capacity factor regions they offer a wind resource that is remarkably predictable and reliable. Texas could easily become a major exporter of electricity.
Solar City on Grid Backup efforts:
Study comparing peakers and storage.