Yes, electric instantaneous water heaters are energy efficient and environmentally responsible. This has been examined and confirmed by various studies, such as "Reduzierung von Energieverbrauch und CO2-Emissionen durch dezentrale elektrische Warmwasserversorgung" [Reduction of energy consumption and CO2 emissions through decentralised electric DHW provision] by the FfE Forschungsgesellschaft für Energiewirtschaft mbH [research institute for the energy industry].
The major benefit of decentralised DHW heating lies in the proximity to the draw-off point. Short pipe runs ensure that heat loss is reduced to a minimum and that hot water is available quickly when it is drawn off next. Instantaneous water heaters only ever heat the amount of hot water that is currently required. Compared with centralised systems, this results in no cylinder or standby energy losses. Neither are there any energy losses for distribution or DHW circulation lines. The bottom line is that electronic instantaneous water heaters save energy, water and costs.