CO2 molecule
A large percentage of energy use in a home is for heating water. Most water heaters either burn natural gas, or use electricity to generate heat. Natural gas is a fossil fuel that creates large amounts of CO2 when combusted, which contributes to global warming, and puts toxic heavy metals into the air we breath. Electricity is primarily generated by the combustion of either coal or natural gas at power plants. So, however you slice it, burning natural gas or using electricity to heat your water contributes to CO2 emissions in a big way.
In San Diego, we have ample sun for generating more hot water than we know what to do with. Solar water heating is a mature technology, and in sunny parts of the world it is the obvious choice to utilize this free source of energy to heat our water in an environmentally friendly way.