Here in Maine, we are approximately at the 45th parallel which means that we have significant seasonal changes in solar elevation from winter to summer. At the spring and fall equinoxes the sun is approximately 45° elevation at noon. This means that the available solar energy in the winter is approximately 25% of the maximum solar energy available in the summer. This is best explained graphically by this chart taken from my TED energy monitor:
The blue bars show the kilowatt hours that we import from our electric utility. The yellow bars show the amount of solar energy actually produced by our 5.7 kW solar array, and the green bars show the net amount of energy that we pay for. Clearly our electric bills drop to near zero in the summer, and since we have an electric vehicle we need to charge your round our bills peak at around $100 per month in the winter. At this time of year it is always nice to see our solar energy increasing, and our electric bills dropping.