John Timmer, writing for Ars Technica:
The fuel savings from not running the fossil fuel plants adds up to $7 billion, meaning the added costs are, at most, two percent of the savings. The fuel burned when spinning up the fossil fuel plants also makes a minimal contribution to pollution, either in the form of CO2 or in terms of nitrogen and sulfur compounds.
Perhaps the most significant news, however, is that the worst problems come earlier in the transition to renewables. “In terms of cycling costs,” the report notes, “there may be a big step in going from 0 percent to 13 percent wind/solar but a much smaller step in going from 13 percent to 33 percent.” In other words, once the percentage of renewables reaches a critical point, then the amount of adjustments we have to make becomes incremental.
Perhaps the hardest part of the transition from fossil fuels to renewables is the shift in costs from long- to short-term. Fossil fuel energy requires constant feeding to produce; most renewables do not. Low up-front costs are appealing to consumers, but clever financing models may shift that equation, which could help push renewables them through those tipping points.