Instant electric hot water heaters (sometimes referred to as on-demand or tankless) provide hot water on demand by heating water instantly as it travels through the unit. They do not store heated water for use at a later time. This makes them quite efficient as you’re only using energy when you need it. Larger households with significant hot water needs can experience issues as a tankless system won’t keep up with demand. However, you can install multiple units to overcome these issues and they don’t take up much space. They are rated in terms of how much water is heated per minute e.g. 4.6 litres/min and should be selected as such opposed to the tank size in a storage water heater.