Sizing a Solar Hot Water Heating System
Sizing your solar water heating system basically involves determining
the total collector area and the storage volume you'll need to
meet 80%–100% of your household's hot water needs during
sunny days.
Solar Collector Area
Contractors usually use a guideline of around 40 square feet (4
square meters) of collector area for the first two persons. For
every additional person, add 14 square feet (1.5 square meters).
Storage Volume
A small storage tank (50- to 60-gallon) is usually sufficient
for one to three people. A medium storage tank (80-gallon) works
well for three to four people. A large tank is appropriate for
four to six people.
For active systems, the size of the solar storage tank increases
with the size of the collector—typically 1.5 gallons per
square foot of collector. This helps prevent the system from overheating
when the demand for hot water is low. In very warm, sunny climates,
some experts suggest that the ratio should be increased to as
much as 2 gallons of storage to 1 square foot of collector area.