Expensive and turbines wear and get iced in winter
Where I come from, solar energy doesn't work in the winter, but wind (large scale) usually does. Output difference of a solar system between winter lowest vs summer highest is ~30x, as we get an average of around 20 hours of sunshine in the entire month of December and it's not exactly at a great angle for those few hours. Wind would be pretty much the only way one could really stop relying on fossil based energy here. Kinda sucks if they're not a real option.