Solar hot water systems make sense in upstate New York, where they can provide at least 50% to 60% of your hot water needs.
Combined residential installation, near Ithaca, NY, featuring both solar flatplate collector water heating panels (center; above chimney) and pholtovoltaic panels for electricity.
Another residential installation, also near Ithaca, using pholtovoltaic panels along with an evacuated tube hot water heating unit (upper left).