What shower rating gives optimal balance between efficiency and running
cost? My current shower is an 8.5kW unit and while output is moderate it
performs reasonably well. For my new house I am thinking of fitting bigger
rated unit, 9.5 or 10.5kW. It says the bigger the wattage the greater the
flow, so in theory you cut down on the length of time the unit is on. But
surely it will use more electricity per shower? And will it not use more
water because of bigger flow rate (water at my new property is metered). I'm
getting confused - can't work out the equation between electricity cost,
water charge and comfort/efficiency. Can anyone point me in the right
Bigger is better; they all (I theenk) can be run at less than max power.
However even a 10.5 has problems raising bitter cold winter water to a nice
temperature at a decent flow rate- it's the price you pay for this sort of
The power rating makes no difference, it's just that higher power can get
more water hotter, but it's how much flow and how hot you choose that
dictates cost, but a smaller shower will only get cold water up to a decent
temp at a dribble.
You will always wish you have more power in winter
A higher Wattage will give you an increase in water flow rate, due to the
fact that the water heats more quickly in the higher rated shower, so you
will be able to turn the flow rate up a bit to increase the output at the
If you can imagine, for example, a normal kettle with a 1.5kW heating
element. The water in the kettle will take, lets say, 5 minutes to boils.
Now put a 9.5kW heating element in the kettle and it will boil in, say, 1
minute. Well the same principle is happening inside the heating tank in a
shower, therefore, less time to heat means increased flow rate at the
Using the above example, you'll see that the increase in water flow rate
will give a more powerful shower, and, if the same principle could be
applied, it should rinse you down quicker. :-)) No, I don't think that's
what does happen either.
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