There are many ways to harvest the sun’s energy, whether by focusing its rays on water-filled pipes, reflecting it to a tower for collection in concentrated form at high temperatures, or, most familiarly, with photovoltaic (PV) panels. (Another, more traditional way, to collect solar energy is via biological processes; we call these systems “trees”.)

Some of these approaches are only practical at very large scale. For residential installations, there are really only two options, each serving a different purpose. Most commonly, PV panels are placed on a rooftop (or sometimes, ground-mounted) to generate electricity, which can then either be stored in an on-site battery for use as needed, or fed back to the power grid.

A second way to harvest the sun’s energy is via hot water collectors, which use a trough-shaped mirror to focus sunlight on a pipe carrying circulating water. These can provide heated water either for daily use or, in some climates, for space heating.