[bluGill]

Generally the worst case is two weeks. In the middle of winter you often get cloudy low wind days for that long. Of course how you handle those worse cases are days need not be how you handle typical. If you can handle 16 hours of no input this will over the typical cases this will be enough to max a massive dent in carbon emissions and we can fall back to existing gas (or even coal) plants for the rest. Plus a lot of power use can turn off when needed - give my company a discount and we can turn the factory off.