Every household, and every business relies on hot water. Our central heating systems are mostly run with hot water, and it is used regularly for washing and cleaning. It is also one of the areas in which solar power is starting to prove useful, even in a domestic setting.
Water is heated using electricity all the time - kettles are a great example. This is a sporadic water heating need. However, hot water is also needed in a more constant way, via a boiler. This latter use is what is required for most central heating systems. It is usually provided by some kind of fossil fuel - coal, wood, or gas. Natural gas is the most commonly used fuel in the UK. However, electric heaters, which heat water on demand, are also widely used.
Increasingly, solar technology is being used for water heating. Solar panels are connected directly to a water tank and pipes the take the water heated by the sun into the main boiler. It is very unusual for solar energy to heat all the water needed in an office or house. The sun is not always up, of course! A convection boiler is usually used to "top up" the hot water needed.
Water heating is a thermodynamic process that uses an energy source to heat water above its initial temperature. Typical domestic uses of hot water include cooking, cleaning, bathing, and space heating. In industry, hot water and water heated to steam have many uses.