Solar hot water systems use solar energy to heat water, and they are usually composed of solar thermal collectors, a water storage tank, interconnecting pipes and a fluid system to move the heat from the collector to the tank.
Solar hot water systems do not use solar energy to generate electricity like this is the case with photovoltaics, they use solar energy to directly heat the water, and therefore no electricity is generated in the process.
Though solar hot water systems do not generate electricity some types of solar hot water systems use electricity to pump the water.
Solar hot water systems reduce our dependence on fossil fuels, and with it help our environment by reducing carbon emissions (greenhouse gases) and air pollution levels.
Israel and Spain were the two first countries to require the installation of solar hot water systems in new buildings couple of years ago.
Solar hot water systems are the cheapest in China, with the average price below $200 and this is the main reason of their increased popularity in China (compared to prices of solar hot water systems in western countries Chinese solar hot water systems are around 75% cheaper). More than 30 million households in China have them already installed.
The most popular solar hot water systems are the ones that have the evacuated tube systems because they enable heaters to function even under gray skies and at temperatures below freezing point.
The amount of heat delivered by a solar hot water system depend upon an insolation in certain area. Tropical areas usually have the highest insolation values.
In sunny warm places (like tropics) solar hot water systems can be highly cost effective.
Though initial costs for solar hot water systems can be relatively high offsetting these expenses isn't usually longer than ten years.
The most important factors when calculating payback period for solar hot water system are: * Price of purchasing solar hot water system * Efficiency of solar hot water system * Installation costs * State or government subsidy for installation of a solar hot water system * Price of electricity per kW.h * Number of kW.h of electricity used per month by your household * Annual tax rebates or subsidy for using renewable energy * Annual maintenance cost of solar hot water system * Savings in annual maintenenance of conventional water heating system