But as drier, hotter conditions have stoked bigger wildfires, the dirty smoke from those fires presents a challenge to solar power generation. It deposits ash and dust on the photovoltaic panels and prevents sunlight from reaching their cells, cutting electricity production. Indeed, in California, wildfires drove at least a 13% decline in solar generation on the grid during two weeks in September 2020, with some systems producing no solar power at all. In Australia, the bushfire-driven decline proved even more dramatic — as much as 45% in Sydney and Canberra on days with heavy smoke. In both locations, the electricity shortfalls forced utilities to ramp up or import electricity generated from coal or other fossil fuels, thus adding to carbon emissions.