31-01-13, 12:12 AM
A comfortable shower temperature will be about 40ºC, in winter the incoming water can be about 5º so your heater needs to raise the temp by 35º. Water takes a lot of energy to warm up, 4.2 joules per degree per cc. So a 10.5kW heater will get just 4.3 litres per minute to a comfortable temperate. A decent flow rate for a shower is about twice that.
Unless you can preheat the water somehow, an electric shower is bound to seem a bit feeble in winter.
Unless you can preheat the water somehow, an electric shower is bound to seem a bit feeble in winter.