Q:

How much money will I save per year?

A:

Most residential solar water heating systems (SDHWS) are designed to provide approximately 50% of the water heating load. For a family of 2, typically 1 solar collector would be used and the savings could amount to as much as $50 - $60 per year, if you were heating with natural gas (Sept. 2016). For 3-5 adults, 2 solar collectors would be used, and the savings could be as much as $120 per year - again if you were heating with natural gas (Sept. 2016). Larger families would require larger solar systems. Adding collectors - while keeping the same load - provides diminishing returns. For example, adding a third collector to a 2 collector system, does not provide 50% more energy if the hot water load and storage volume stay the same. Typically a gain of 20 to 25% will be achieved. Adding a fourth collector will only improve the performance by about 15%.

If you heat your water using electricity, your savings will be about 300% greater (Sept. 2016) than those who heat with natural gas

Evacuated tube collectors will not save more money than flat plate solar collectors in SDHWS - and will save less if the collector area is smaller.