Hot water cylinders are available in a variety of sizes and heat the water in the cylinder using a number of different methods. Each cylinder is sized based on how much water it can hold, typically varying from 80 litres to 300 litres. Each cylinder is also placed into different categories; vented or unvented and direct or indirect.
Using the immersion element in a water cylinder, the water is heated up in a similar way that a kettle boils water. The immersion element has a thermostat inside which only allows the immersion element to heat the water up to the desired temperature (typically 55 degrees Celsius). Once the cylinder temperature is achieved, the immersion element will switch itself off and on, to maintain the desired temperature in the cylinder. This will continue throughout the day unless a timer is fitted to control when the immersion element can be activated. This allows you to heat the cylinder water up solely in the Economy 12 low rate, therefore saving money on your electricity bill.