Water heating

  LinH 13:28 14 Nov 2010

A question for the economists here:

At present we have our water heated twice a day for about two hours each time. The question is, would it be as, or more, economical to leave it on permanently?

If it helps the water temperature is set at about 55ish degrees C and the house is occupied for most of the week.

Nothing serious here, just interested in what others think.


  Forum Editor 13:38 14 Nov 2010

on how you heat the water.

If you have an electric immersion heater in a water storage cylinder then it would be better to leave it on all day.

If you heat water via a central heating boiler, and the water is stored in a cylinder with a primary coil inside, it would pay to leave the boiler timer set to constant on the hot water programme, and let the cylinder stat cycle the boiler on and off to maintain the temperature.

If you had a combi boiler the question wouldn't arise, because you would heat water on demand, and this is the most economical method.

  LinH 13:57 14 Nov 2010

FE: We have the second option i.e. cylinder with primary coil by gas.

I find it interesting because when discussing it with friends their opinions seem mixed, some tend toward the permanent option whilst others prefer the on/off scenario.

I could, of course, try each option for a quarter to see the difference in bills but things like price increases/decreases, summer/winter usage etc would make it tricky to definitively quantify it.


  sunnystaines 14:09 14 Nov 2010

we use on/ff as needed

  lotvic 14:35 14 Nov 2010

I've got same setup as LinH and set at 55c as well.
I also keep wondering which is best way to do it. At present have to put it on for an odd hour extra when a bath is run for instance - darned nuisance when I forget and then run out of hot water.
Been thinking of changing to a combi but wonder how long it will be before costs break even (installation costs) as present boiler is less than 2 years old and still under guarantee.
I moved into this place a year ago and need new bathroom design and could do with the space that cylinder cupboard takes up.

  peter99co 15:51 14 Nov 2010

I have a water heater on at 6.00 (Economy7) for 1 hour and at 18.00 for half hour. Seems just right.

  spuds 15:58 14 Nov 2010

We also have the same method as LinH and lotvic, and after asking the same questions with energy advisor's, we seem to get slightly different opinions. In the warmer months we have timers set for 2 hours in the morning before we get up, and then set for about 6pm for an hour. Not being big hot water wasters, we find the above adequate for our needs.

In the colder months, then we leave the 'whole' system on, which balance itself out, depending on the house 'set' temperature and the water 'set' temperature.

Should there ever be a problem with water heating on our property, we have an immersion heater with timer in the water cylinder. But I cannot recall ever having to use this. One thing that the experts agree, this would be the most expensive way to heat water for domestic use, more so if the water is allowed to get cold and you heat from the start.

  spuds 16:03 14 Nov 2010

One thing that I forgot to mention, is that I was seeing a report the other day regarding certain types of solar heating.

Some of the people involved were able to provide for all their needs of heating, lighting etc and even sell back surplus electricity to the national grid.

Perhaps that might be the way forward?.

  LinH 16:59 14 Nov 2010

An interesting spread of replies that more or less mirrors similar discussions had with friends.

I'd just mention to spuds that we also have a standby immersion heater and although rarely used it proved invaluable recently when the pump went u/s. You can live without heating for a few days but without hot water, definitely not. So spuds, don't get rid of it just yet!

Cheers all.


  natdoor 18:28 14 Nov 2010

I believe that the recommended temperature is 60 C to avoid the risk of Legionaires' Disease.

  Forum Editor 18:34 14 Nov 2010

is a simple one - what's the point of heating water, only to let it cool, and have to be heated all over again?

The boiler will consume less gas if it is allowed to cycle on and off, maintaining the water at the required temperature, rather than having to work hard to heat water that has been cooling all day or all night. The only justification for the twice a day heating cycle is if the hot water in the cylinder is used up each time. In that situation you'll be heating water from cold anyway.

The other factor in all this is the amount of efficient insulation around the cylinder - if you don't have a spray-lagged cylinder make sure that you have a high-efficiency blanket that completely covers it.

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