How do I size a solar hot water system for my household?

Typically, an american average consumption of 20 gallons of hot water per day per person can be used to size systems. There are some variations in that however, so we need to be careful about just using rules of thumb. Most of the Sunmaxx TitanPower flat plates and Thermopower evacuated tubes will yield about 2 gallons of hot water per square foot of collector. Therefore, we can say that for a family of 3, we would recommend about 30 ft of collector. This estimate will vary depending on the climate. If you live in the northern climates, this system example would replace existing fuel by over 50%. In mid-latitudes, you could expect a 60-70% reduction and in southern climates, as much as an 85% reduction.