Solar water heater systems are systems for storage, it depends on your weather condition, it could offer you more than 90 percent of your hot water free from the sun power. Solar water heater systems cost a little more to buy and install compare with other water heating systems, but it can save more energy and save your bill.
To provide hot water on cloudy days or rainy days or when require extra supply, most solar water heaters has a gas or electric heater.
The solar collector and storage tank is normally installed on the roof of your house, facing north. The storage tank could also be put inside house.
Natural gas water heaters cause less greenhouse gas emissions than electric heating storage systems which adopt mainland grid electricity. It is because natural gas burns cleaner than the coal that is burnt.
Gas storage water heating systems have immdeiately heat recovery times and normally use a smaller tank. It improves the efficiency and make it more easy for installation.
Electricity could be used for popular storage water heaters, for heat pump systems or boosting solar systems. Usually, an expensive three-phase electricity supply is required for those systems.
Electricity is not used directly to heat cold water but to move the refrigerant around the system. That's why the electricity consume is much less than for storage systems.
Compare with solar water heaters, an electric storage water heater may be cheap to buy, but it may be expensive to operate and this needs to be taken into consideration when deciding which water heater to choose.