Even if you live in a tropical region, you’ve got to make a provision for the odd cold and cloudy day, if you are looking at installing solar hot water.  Boosters use gas or electricity to heat up the water to the desired temperature on days when the sunlight is insufficient.

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The advantage of an electric booster is that it is relatively inexpensive to install, but has a higher running cost. Also, it consumes more energy as it heats water in the tank as soon as the temperature drops below the setting, regardless of demand.