A hot water system heats and stores water in a tank, or heats it as needed through a continuous-flow unit, then sends it to taps and showers when you open them. Common Australian options include electric and gas storage systems, instantaneous gas units, heat pumps and solar hot water systems. Each has different installation requirements, running costs, capacity and maintenance needs. The most suitable choice depends on your household size, energy supply, available space, climate and budget, so compare models and ask a licensed plumber for advice before replacing one.