Maybe a silly question about heating water

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Mers1

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All,

Forgive me if this is a stupid question. A while ago I had heard that it was cheaper to leave you immersion on "sink" all of the time rather than turning it on when and as you wanted hot water. I have just heard this argument again this weekend, Is there any truth in this????

Any views greatly appreciated.
 
If you leave the immersion on all the time then your bill is going to be huge. It is better to heat as much water as you need when you need it and then use it. If you are on a night/day meter setup then you will probably be better off heating water during off peak hours (between 11PM and 8AM or 12AM and 9AM).

If you want to check for yourself then maybe try leaving the immersion on for a week and monitor your electricity usage at the meter. Then try heating water on demand for a week and compare the two. Obviously other electricity usage and environmental factors will skew the results but it should give you some idea of the cost of leaving the immersion on all the time. Expensive way to check though!
 
My thoughts also Clubman! it was really to see if anyone had done this and if in fact it was cheaper.
 
If you have a well-lagged tank, you should be able to leave it on.

Immersion have thermostats. Even tho its 'on' constantly, it is only using power when the immersion kicks in when the temp drops below the setting.

So, if you are well lagged you are not losing much heat except for the little bit that is airing your clothes anyway, plus whatever hot water you draw off.

The immersion may kick in for a couple of minutes every so often but its the total time that counts out of the 24 hours.

So I don't see why it should be huge.

I asked my plumber about this before and he agreed.

BUt if anyone has done the experiment then fair enough, I stand corrected.
 
I would be interested in somebody doing this experiment and reporting back. I would be pretty sure that in the two scenarios that I outlined the "heat/use on demand" one would be the cheaper by a long shot even with good insulation unless the "on demand" times were coming thick and fast throughout the day/week.
 
If you put x watts of power into the tank, whether in several short blasts or one big blast, then surely it amounts to the same thing?

The only way you end up putting extra in is through the amount that escapes through the lagging which should not be much - but most people consider this not to be waste as they want some heat for clothes airing.

Some people even leave the lagging off for this reason but that is overkill.

If you only use hot water once or twice a day then I guess it could save a bit , although inconvenient unless you are v regular and set up timers to suit.

- but if anyone is at home all day then the inconvenience makes it a real pain to be switching on and off constantly.

Of course if you have night rate then you should definitely NOT leave the immersion on full time, as approx 50% of your usage will be day rate, for no good reason.
 
Okay, several short blasts are the same as one big blast from a KW usage perspective.

However - there will be a greater energy loss if it is left on all day(asuming my logic is correct on this). The greater the temperature differential between two things the great the rate of loss of temperature. So if you keep heating it up so it constantly very hot, then you will be always lossing at the greater rate. [I think it's Newton, but think a cup of coffee, if you take milk and know that you won't be drinking it for 10 min, you add the milk in at the start - not just before you drink it to minimise the heat loss]

Now if it's incredibly well insulated - that's one thing. I'm thinking the factory insulated. IMHO leaving the insulation off so you've a warm boiler is mad - a bit like turning on the ring of the cooker and standing with your hands over it to warm them up. If someone

There's a thread here that goes through some of this.

Since reading through some of these threads I now only ever use the sink option, on for 10 minutes is enough to heat it up for a shower for me.

Note - check the temperature of your hot water too - if it's too hot so you need to mix it with cool water to have a shower, then you're over heating it and are just throwing money out.
 
Even a factory lagged tank will lose heat through the immersion elements caps, the connecting pipes etc.
 
A well lagged large cylinder; heated by time control to demand is best, a small volume will drop to low tempature faster. Heating to demand is critical in summer as any heat loss in winter is a gain to the building.

Per kW electricity is; twice as expensive oil; 3 times that of natural gas; and 4 times that of woodpellet
 
OK, I agree with dem_syph esp on the basic thermodynamics bit.

Some great info in these posts, and I am going to turn down my stat as it has made me think about heat loss at higher temps.

But I just wonder what I am meant to do if anyone wants to wash their hands in hot water every time they use the bathroom or just in general washes their hands? Do they flick the immersion on for 3 minutes beforehand? Likewise each time for washing breakfast, lunch, dinner, supper dishes.

And then sure any extra hot water is in the tank until the next time, so it kind of defeats the purpose.

I think there is a commonsense factor but also a convenience factor at play here.
 
eamonn123456 said:
But I just wonder what I am meant to do if anyone wants to wash their hands in hot water every time they use the bathroom or just in general washes their hands? Do they flick the immersion on for 3 minutes beforehand? Likewise each time for washing breakfast, lunch, dinner, supper dishes.
Click to expand...
You might be better off boiling a kettle for some or all of those purposes.
 
Yeah true for washing dishes, no loss of energy from hot water lying in the pipes, but for family handwashing?? Not sure that makes much sense, from a convenience, hygiene or safety p.o.v.

Each to their own tho, lots of good ideas coming out.
 
Once you use soap I would assume that cold water will work just as well to wash your hands?
 
eamonn123456 said:
Yeah true for washing dishes, no loss of energy from hot water lying in the pipes, but for family handwashing?? Not sure that makes much sense, from a convenience, hygiene or safety p.o.v.

Each to their own tho, lots of good ideas coming out.
Click to expand...

Why would you need hot water to wash your hands?
 
Sorry, I understood that ClubMan was advocating boiling a kettle of water for handwashing purposes.

I guess one can use cold as long as one uses soap, so no actual *need* for hot water for any hygiene purpose.

It's just a little luxury that many people take for granted, just like a hot bath or warm shower or electric light ;-)

And yes of course we can traipse around with kettles of boiling water for shaving and whatever. Not a great option if you have children or elderly people in the home. Each to their own as I say.

Definitely gonna start boiling the kettle for dishes tho - at least you know exactly how much you have boiled that way, and no need to waste any.
 
Do you have a back boiler Eamonn?

Maybe not cold enough yet, but we have found that when lighting fires obviously the house is heated and hot water provided but also, there is generally enough hot water the next morning for shower/shave and even enough for about one basin of hot water for dishes the following evening.

No-one in the house using water during the day though.

Our immersion is on timer these days for the mornings and the only other time it's really used is for the occasional bath. Generally, we would boil a kettle for dishes when required.
 
I am interested in the outcome of this thread as I am having similar problem with new house. Immersion heats the water [even after 15 mins ok for 1 shower].
I have been told by builders [as I asked them to install timer on immersion] to turn on the gas boiler to heat water[ and turn down thermostat on walls that work the radiators] - this will heat water in tank more efficiently than immersion, and will not heat the rads.
in practice - 1 hour of gas being on only gives me a lukewarm shower.
I have tried it with rads on at its the same.
do you think there is something wrong or is that normal for gas. not sure myself as never had gas before. thanks
 
Warm water is recommended for washing hands - 40 degrees. So is washing your hands for 20 seconds - and very few people do that!

If I'd kids, I'd be more concerned about them scalding themselves - you can control your house, but when they're out... Unless you've a mixer for your taps the water may be too hot for them.

My gas/electricity bills are lower now than 8 years ago down to changing habbits. I still have warm showers, hot tea and electric lighting. For this I'm okay with washing my hands in cooler water - I get a warm glow from knowing I use less energy ;)
 
pinkie123 said:
I am interested in the outcome of this thread as I am having similar problem with new house. Immersion heats the water [even after 15 mins ok for 1 shower].
I have been told by builders [as I asked them to install timer on immersion] to turn on the gas boiler to heat water[ and turn down thermostat on walls that work the radiators] - this will heat water in tank more efficiently than immersion, and will not heat the rads.
in practice - 1 hour of gas being on only gives me a lukewarm shower.
I have tried it with rads on at its the same.
do you think there is something wrong or is that normal for gas. not sure myself as never had gas before. thanks
Click to expand...

Something's set up wrong. 15 minutes is sufficient for 1 person for the shower in my opinion. I'm assuming that you've a lever in beside your tank that you switch between heating the whole system and just the water? This needs to be set to the water only. Then turn the thermostat up so that the gas boiler will stay on for the 15 minutes. All it is, is a sensor checking the temperature of the room - it's designed for the heating versus monitoring the temperature of the water. So when you're turning it down, the boiler is going off so you're not heating anything.

*disclaimer - I'm only a user. I'm assuming that there isn't a way of changing the specific temperature that a gas boiler will heat water too. My systems 10-15 years old and I'm pretty sure that's how mine works.

When looking at prices of gas/electricity and which is most efficient there are different rates for both - don't take what someone else tells you, work it out for your case. Similarly - check you're on the correct rate for your use levels.
 
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