Electric showers typically have one consistent advantage - they are independent to the hot water heating system. This can provide a good back-up in the event of boiler failure and furthermore prevents hot water being drained from a storage tank or a drop in pressure where two showers are in use at the same time. Since an electric shower only requires a cold water feed the unit is mechanical and works to heat the water up instantaneously thus needing electricity. The suitable Kw rating will depend largely on the specific wiring supplying the shower. Consult your installer first for his specific recommendation or contact us direct for more information.