What will be the investment for Solar Energy plant for Water Heater and Home domestic appliances?

I would suggest that you consider installing two different solar devises; one for heating and one for electricity. Water can be heated by collecting solar energy in a panel that allows sunlight to pass through a treated glass or plastic pane and shine on a black convoluted surface that avoids reflection. The heat produced can not escapes as easily as sunlight enters. This is the greenhouse effect that heats your car on a rather cool day. Inside the solar panel there are tubes or pipes that circulate cooling water to carry off the heat to an insulated storage tank. In cold regions the cooling water must contain antifreeze. The panel shoud be placed on a roof nearly perpendicular to a line from the sun at noon durning the cold season. In the upper USA that would be a southern exposure. The solar panel can be used to pre-heat water that is further heated by an electric or gas waterheater. The number of panels you will need will depend on the number of people using hot water and whether you use it as the sole source of warm water or as preheat. Expect panels to cost hundreds of dollars, depending on whether you install them yourself. For electrical loads, you should consider installing photovoltaic solar panels which produce direct current (DC). This can be used for heating water or running electrical equipment and lights but heating may use up the entire capacity of the panel(s). You may need a battery to store energy and a converter to provide the correct voltage (and AC?) as desired. Expect voltaic solar panels to cost less as new technologies come to market. DayStar is building a factory now to produce cheaper continuous film cells (that could cover a roof?). The wattage for various items you wish to power is usually included on the manufacturer's identification plate and depends on the size and model you have or wish to buy. Good luck.

Domestic solar water heaters work on the tenet of thermosyphonic impact. Circulation of water from the tank through the collectors and back to the tank continues mechanically owing to density distinction between hot and icy water. No electricity is critical for circulation of water or for the other operation in such systems. However, just in case a back up heater is provided to require care of plight demand in the cloudy days, electricity is going to be necessary.