Solar water heating systems usually integrate with a traditional gas or electric water heater. During times of high hot water demand, or low levels of solar energy, the “backup” water heater compensates. During times of the year when there is more sun, the solar contribution is higher, and during times of the year when there is less sun, the solar contribution is lower. Take a look at the chart below to see an example for a system that is producing 60 gallons per day of 120F water, with a natural gas water heater as backup, in San Diego, CA.
