15Jan

Energy Tweak

Changing our showerhead

I got one of these gadgets for Christmas, looked interesting and got me pondering. Setting it up requires measuring the flow rate of your shower which in our case was 10L/min. A few weeks ago I remembered reading a review of showerheads (!!!) - but it was in the Architects Journal 'Sustainability in Practice' pages (26.11.09). Water saving showerheads ranged from 3.5 to 9.6 L/min so our existing showerhead was just at the top end of the range. A quick swap of heads to the best rated version, the 'Mira Eco', revealed a flow rate of 6L/min rather than 3.5L/min - I guess this is down the water pressure.

A few sums revealed the benefit of the swap:

With a shower time of 5mins at 10L/min we use 50L of water, at 6L/min we use 30L of water.
To heat 1L of water by 1°C requires 4180 Joules of energy.
To heat 1L of water from 10°C to 35°C takes 104,500 Joules = 0.029 kW
Our mains gas boiler in 90% efficient so we would in fact be using 0.032 kW of gas per litre.
So by using 20L less water we are saving 0.64 kW of gas per shower.
Lets say our household has 3 showers per day, 300 days per year = 900 showers/year.
Our annual saving is therefore about 576 kW which equates to 106 kg of CO_2.
We pay about 5p per kW for our gas so annually we will save about £29.
With the showerhead costing about £30 the payback is quick at 1 year.

If our existing showerhead had been operating at 20L/min the saving per year would be 1827 kW or 336 kg of CO₂ or £91 which of course doesn't include the other costs involved in having a shower, namely the water, electricity and system losses. Either way, probably worth the effort.

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Softwood Timber merchants

27 October 2010 at 09:09 | #

Its good that more is being done to improve the sustainability of our homes. I currently use a showerhead which receycles some of the water used.

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