These types of dispensers are energy-saving because they don't need to store hot water, which will inevitably dissipate to the surrounding environment over time, no matter how well insulated it is. The water temperature in a storage water dispenser is still much higher than the Room temperature. If you plug it in to keep it warm, there will be energy consumption for keeping it warm. If you don't plug it in to keep it warm, the water in the dispenser will slowly become cold water, which is still a waste.
Instant water dispensers heat a relatively small amount of water each time; They only need to heat the water we need. There is no need to heat a large bucket of water like a storage water dispenser. The amount of water heated is small, which is naturally energy-saving.
Instant water dispensers must be installed very close to the point of use, so there is no need to go through long pipes before hot water appears, and it will not get cold while delivering hot water. You must have an instant heater for each sink to achieve this efficiency. Once you start extending pipes, sharing a heater to multiple outlets, or having a local hot water tank storage to help achieve the "instant" part of the description, these benefits disappear.