In winter, depending on snow, latitude and the size of the system, solar may not help. I have a 6kW system, which offsets my AC use in the summer (about 1mWh generated in June and July), but I get very little at a 42 degree north latitude, usually less than 100kWh in January and December. There was one February recently where the system was covered in snow all month and I generated a goose-egg.