Rooftop solar arrays, rainwater catchment systems, a hotwater recycling pump, sliding sunscreens, trellises and a few other features are optional upgrades.
Solar thermal heat is ideal as an auxiliary system to existing furnaces and hotwater systems -your furnace or water heater operates exactly the same as it always has, coming on and running in response to thermostat settings to keep your house or water heated to the thermostat setting.