Trying to find out how long in the 9kw elec shower equates to a bath of water drawn from the cylinder heated by new condesing boiler.
Just a rough idea would help a family argument!
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There's this ............. www.eswater.co.uk/Showerenergycalculator.aspx .......... and this ............. www.lenntech.com/calculators/energy/energy-cost-water.htm
All you need now is pencil and paper to write down the results.
Last edited by: L'escargot on Sat 12 Jun 10 at 12:20
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I would think, that the much smaller amount of hot water used by a shower, would always be cheaper.
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You haven't seen how long my daughter can spend in a shower.
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A shower is only a warm tap, so if you run it for many more than 10 minutes, you've heated enough water for a bath.
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The average shower is about two minutes, Thats only 20% of a bath for a kick off. Given that the flow through a shower head is less than a tap - about 10% (due to back pressure of the small holes) thats less water used.
Look at it like this. If you opened up your 20mm bath taps into a shower tray it would soon over flow, even with the plug out. Or try filling your bath with the shower attachemnt!
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>> You haven't seen how long my daughter can spend in a shower.
Not just daughters...............
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>> You haven't seen how long my daughter can spend in a shower.
>>
When she gets married, don't think of it as losing a daughter, but gaining a bathroom.
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When she gets married
Apparently fathers will have to provide an EPC with their daughters before the marriage under EU proposals.
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www.consumerenergycenter.org/myths/shower_vs_bath.html
It depends... but gas is cheaper per kw. It also would depend on size of bath and the fill height you chose and also how much hot vs how much cold you would use to get it to the required temperature. A bath would also take a fixed amount of water.
Also a 9KW shower would put more strain on the electricity grid. That's 3 powerful kettles worth!
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Thanks for the links L'escargot & teabelly... I'll give them a look later.
>>>You haven't seen how long my daughter can spend in a shower.
>>>The average shower is about two minutes
>>>I would think, that the much smaller amount of hot water used by a shower, would always be cheaper.
Hmmm you see that's the issue in our house. Spent a fair bit on a bathroom upgrade to include a new 9kw elec shower and bath more suited to standing in for a shower. Previously we'd used the old bath with hot water from a cylinder heated by gas boiler.
Just had 1st elec bill since shower was fitted and it's up by 30%. When we look at it I think it's down to teenage girls standing under the shower for long periods... perhaps up to 15/20 mins. 9kw for that length of time is going to add up once a day (or twice on a going out night) for two girls
How I wish I'd had the shower isolator switch outside the bathroom as one way the sparky offered to do the job.... then I could have enforced the 3 min rule.
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Its not to late to modify it.
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>>>Its not to late to modify it.
Indeed but by chance I've just gone to turn off the outbuildings elec feed at the consumer unit to fit a new outside light and realised the shower is on its own circuit so I can set the kitchen timer and then flip the shower feed off at 3 mins... we'll see how the little high spending darlings get on with that!
As a matter of interest I fitted up one of those remote elec usage monitors the other week... means I'm now forever rushing about the place to see "who's using all that electricity"!!
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Just get one of these, put it in the middle of the kitchen floor, and make them share it.
Just like the good old days. :-)
www.mowermagic.co.uk/acatalog/GALVANISED_TIN_BATH_54.html
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Ahh remember them well from my earliest days as a child. In Grandad's house you took a bath in the scullery. It was a tin one as in your link, the water was drawn from a well in the floor of the room and heated on a solid fuel "copper" which was otherwise the way they washed clothes. There was no piped water in the place... you had to go about ten houses down to the village standpipe (looked like cast iron toadstool thing).
And do the girls want to hear their Dad's stories about such things.... do they hell.
His toilet was outside and what we called a "bucket and chuckit".... just a flat board with a hole in it over a 5 gallon container... and that awful Izal toilet paper.
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>>and that awful Izal toilet paper.
But try making a kazoo with soft paper and a comb!
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>>His toilet was outside and what we called a "bucket and chuckit".... just a flat board with a hole in it over a 5 gallon container... and that awful Izal toilet paper.
>>
Memories. At my grandmothers cottage, the toilet was at the far end of the garden IIRC about 200 feet from the house. A well built brick **** house attached to the pig sty.
The only plus was that in good weather you could leave the door open and enjoy a lovely country view.
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Back of the envelope calculations. A few assumptions used:
* Shower (gravity) consumes 35 lites of water.
* Bath consumes 80 litres of water. (figures from internet trawl)
* Inlet water temperature is the same for both.
* Shower is at a temperature of 35C (100% efficiency)
* Bath water is put in at 45C (bath is probably at 38C overall, but heat loss when it's filling).
* Modern condensing boilers are near enough 100% efficient anyway.
I reckon having a shower is about 3 times as efficient as having a bath in terms of total energy usage. This doesn't take into account people like me who laze in the bath for an hour, topping it up every few minutes.
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"Warning: Showers can seriously damage your health."
www.theregister.co.uk/2009/09/15/shower_menace/
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No problem... I'll add screenwash additive to the cold tank!
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Given that 'average' household electricity consumption is 8-10 kWh / day then using a 9kW shower for 1/2 hour a day will add 4.5kWh to the consumption - ie nearer 50%. Sounds like you are getting off lightly with only 30% FL!
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Richard.
That's an interesting guideline figure for 24hrs elec. As I mentioned earlier we have an elec monitor and yesterday it showed 15.78kwh total so yes looks to be almost 50% up on the average. The last 7 days look terrible at 126kwh so close to double average.
Further investigation needed.
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A 9kW shower won't use that amount of power all the time that the shower is being used. The water temperature will be thermostatically controlled.
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It will.... at 30°C temp rise, 9kW only generates 4.3l/min of hot water - which is just about acceptable for a shower (and why combi boilers are generally around 30kw - otherwise it would take all week to fill the bath!). When an electric shower is on, it's on at full whack (unless you press the low power button, but I never understood why they have those - it's only just bearable on high power!). To my mind electric showers have very little to recommend them!
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>> When an electric shower is on, it's on at full whack
Yes,. it's the flow rate that determines the temperature ie. turn up the flow rate to decrease the temperature (because the water is spending less time in contact with the heating element).
EDIT: that's on the average electric shower - I think you can buy more expensive ones with proper thermostatic controls as L'esc says
Last edited by: Focus on Tue 15 Jun 10 at 08:37
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"Yes,. it's the flow rate that determines the temperature ie. turn up the flow rate to decrease the temperature (because the water is spending less time in contact with the heating element)."
Sort of.... Q=M cp DT. Q (heat load) is fixed (9kJ/s in this case) cp is fixed* (heat capacity of water - 4.186 kJ/kg °C) so as M goes up (Mass flow, kg/s) DT (temperature change) has to fall to keep the equation in balance. So yes, the time will be reduced, but there will be plenty of area to transfer the heat, so the heat balance equation governs.
* OK the pedants amy argue that it actually changes as the water temp rises but the effect is small. The density changes too, so there is more volume outlet.
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>> but there will be plenty of area to
>> transfer the heat, so the heat balance equation governs.
Don't understand what having 'plenty' of area has to do with it - I mean, it's just a constant. Can you explain?
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>>To my mind electric showers have very little to recommend them!
>>
I avoided fitting one. Instead I have a gravity fed shower that I suspect uses about the same amount of water as a bath.
It took me a lot of installing but I like a shower that has a good flow and I do not want a high impact spray. Tank on stilts and a long twin 22 pipe run to an Aqualisa ( large bore hose) on the ground floor.
To hell with the expense ( I think it dumps two gallons before it is up to temp).
Feeling smug as it has no electric bits, I had to change the thero cartride recently ( not cheap).
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>> Instead I have a gravity fed shower that I suspect uses
>> about the same amount of water as a bath.
We have a power shower that takes hot water from the tank, in what looks and sounds like large quantities. So I use a jug and moan at everyone else :)
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>> Richard.
>>
>> That's an interesting guideline figure for 24hrs elec. As I mentioned earlier we have an
>> elec monitor and yesterday it showed 15.78kwh total so yes looks to be almost 50%
>> up on the average. The last 7 days look terrible at 126kwh so close to
>> double average.
According to my electrical monitor thing, our power consumption has been 79kw for the last 7 days. The biggest daily electrical gobbler upper in our house is the Dishwasher.
Last edited by: Zero on Tue 15 Jun 10 at 09:06
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Get a washing up fairy.
Pat
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>>Get a washing up fairy.
Doesn't give the same sparkle.
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I will waterproof the shed for you to live in, when can you arrive?
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>> Get a washing up fairy.
You called? :)
Actually SWMBO has been complaining recently because when we had our current kitchen fitted I said we didn't need a dishwasher. Now we are trying to sell our house and potential buyers always ask where it is :(
Last edited by: Focus on Tue 15 Jun 10 at 09:44
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For us, ignoring the current running cost issue, the elec shower has sorted issues we've had for a while. The good lady gets up very early for work most days and always baths/showers. With our old setup of the bath with hot from the c/h tank if someone had used loads of water later at night there were howls of protest at 5am due to no hot water.
Also we didn't have a shower at all and we all wanted one... as the head of water is minimal in our upstairs bathroom it would have needed the expense of a pump even if we'd thought of a tank fed shower.
So the bathroom revamp was designed around an elec shower off the cold feed so there was guaranteed hot water any time of day. This is a massive benefit to us.
In truth we are heavy elec users anyway I guess. 90% of clothes are tumble dried all year round, we have a dishwasher and the girls seem to have their hair straightners on all the while.
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"girls seem to have their hair straightners on all the while."
I was surprised to find a while ago (god I'm sad...) that SWMBO's straighteners were only 35W - so you can encourage that!
I can see that there are occasions were fitting an electric shower is a good idea - such as your retrofit FL - but I've seen many modern houses with combi boilers where electric showers have been fitted. Eh???
Me, I junked the gravity HW cylinder and fitted a thermal store - much better (but at a price...) The increase in the efficiency of going to a condensing boiler at the same time just about offset the increase in gas consumption for going to a mains pressure shower.
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Shower vs bath - running cost? - L'escargot
