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Hot water-on a timer or on constant?

(36 Posts)
mckenzie Mon 07-May-12 17:03:30

We usually have the hot water on a timer, just like the central heating. It comes on first thing, goes off when everyone has left for school / work and comes back on in the evening. At the weekends, it's on all day.

DH has just had a cold shower because we forgot that its bank holiday Monday and not the weekend and so now he wants to leave the hot water on constant so that he never has a cold shower ever again.

I say that it's a waste of energy and money but he is saying that it's proven that it's actually more cost effective to keep it heated all the time rather than allow it to cool and then re heat it.

Anyone know the facts about this please?

educatingarti Mon 07-May-12 17:18:23

It is more expensive to have it on permanently.

janek Mon 07-May-12 17:32:25

i agree.

OctoberOctober Mon 07-May-12 17:43:17

I have heard the same thing being true about the heating, cheaper to keep it warm than reheat entirely although I'm not convinced.

Re the hot water, a combo boiler gives hot water on demand without unnecessarily heating water you 'might' need - definitely worth considering if ever replacing boiler.

insancerre Mon 07-May-12 17:45:58

or get an electric shower

Fizzylemonade Mon 07-May-12 17:48:47

This was an answer to a question I asked on another thread, the short answer is it is better on a timer, the long answer from a boiler engineer is this

"modern hot water cylinders are very well insulated and if heated up and left hot, they lose (depending on who you believe) between 0.5kWh/day or 2kWh/day in heat leakage.

That's between 2p and 8p worth of gas per 24 hours. It also helps to lag the hot pipes with Climaflex or similar. You can put one or two red insulating jackets around even a factory-insulated cylinder if you have room, it will cut heat losses slightly more. Due to temporary energy-saving subsidies, you can buy jackets for £3 at the moment, so I'd certainly put two round a plain copper cylinder.

If you run the boiler HW on a timer morning and evening, it will prevent the boiler running repeatedly for short periods each time you fill a sink, which is inefficient. Cylinders usually hold about 100 litres of hot water (about a bathfull) so let the boiler run before and during the times you will be having baths and showers, and it will stay hot the rest of the time.

The lovely boiler engineer reckoned that a modern boiler will take a modern cylinder from cold to hot in about 20 minutes.

Hope that helps.

PuppyMonkey Mon 07-May-12 17:50:57

Combi boiler is what you need.

rubyrubyruby Mon 07-May-12 17:53:29

Message withdrawn at poster's request.

Housewifefromheaven Mon 07-May-12 18:00:29

I saved a fortune (£80 per month) gas by switching the hot water on to an hour in the morning, and an hour in the evening from having it on all day grin

PigletJohn Mon 07-May-12 18:19:32

you must have a very inefficient system then, HWfH.

Seona1973 Mon 07-May-12 18:21:55

we have ours on for a few hours in the morning and a few in the evening and that gives plenty of water for washing/dishes, etc. Does your shower not heat the water for you as ours does?

Duckypoohs Mon 07-May-12 18:30:53

We have an electric shower and only put the boiler on for an hour a night, that's enough for any baths needed, sometimes it's a bit lukewarm for washing up, but just top up with the kettle.

Our gas bills are small in the summer, about £45 a quarter at the most.

MushroomSoup Mon 07-May-12 19:26:18

We have our water on constant but after reading this I'm turning it off!

PigletJohn Mon 07-May-12 19:47:50

50p a day for me in summer, two hours morning and evening. Would have to put it on extra, if people have baths at other times.

Fizzylemonade Mon 07-May-12 19:58:12

When I quoted above I quoted from PigletJohn's advice on another thread, PigletJohn knows what she/he is talking about.

There have been lots of boiler questions on Property/DIY to which PigletJohn has shared her/his extensive knowledge.

Not stalking you at all PigletJohn grin

PigletJohn Mon 07-May-12 19:59:43

I can see you, behind that tree.

mckenzie Mon 07-May-12 20:43:47

thank you everybody. Our system is about 9 years old. We have a boiler downstairs in the utility room and then something upstairs but I don't think it's a tank as such. If the hot water is on (i.e. couple of hours in the morning) the hot water won't run out at all. But oif you use it when the timer is not on, it will run out if you have lengthy showers like my DH does!!

I think I might just go and turn it back to the timer mode without telling him and plead ignorance if he gets a cold shower next bank holiday smile

PigletJohn Tue 08-May-12 00:24:08

I bet you have either a HW Cylinder with a rigid plastic foam insulating shell on it, or a Megaflow or similar with a white metal casing. Megaflows give high-pressure showers and can easily use 10litres/minute of HW .

Your boiler programmer probably has an "advance" or "change" button on it that you can use to put the HW back on "just for today" without changing the time settings.

mckenzie Tue 08-May-12 09:33:31

I think we have the mega flow PJ. It happens about once a year, that one of us forgets its bank holiday or we are showering when we wouldn't normally be and we get a cold shower. I don't think that's s good enough reason to leave it on all the time. Huh? DH seems to think st cheaper to keep it hot constantly than to let it get cold and re heat it. What do you think?

PigletJohn Tue 08-May-12 10:01:28

I agree with

Fizzylemonade Mon 07-May-12 17:48:47

blackteaplease Tue 08-May-12 10:05:23

We have ours on for an hour in the morning and evening and it's fine for two/ three showers and a couple of rounds of dishes/ or an evening bath plus toddler bath before running out. However we have an advance button and it only takes 30 mins to heat the tank back up so we use that if we have visitors.

I wouldn't leave it on all day as that's going to cost a fortune.

rubyrubyruby Tue 08-May-12 10:07:22

Message withdrawn at poster's request.

blackteaplease Tue 08-May-12 10:11:48

rubyrubyruby you won't necessarily have to override to have a shower during the day, only if you have used up the full tank of hot water. If you aren't using much, it will stay hot in the insulated tank.

rubyrubyruby Tue 08-May-12 10:13:57

Message withdrawn at poster's request.

PigletJohn Tue 08-May-12 10:16:15

blackteaplease I wouldn't leave it on all day as that's going to cost a fortune

As long as it is properly insulated and there is a thermostat on the cylinder, it will cost a matter of pence rather than a fortune. If not, then you need to correct those defects. But yes, it will be more efficient to heat it twice a day, since it saves the waste of getting the boiler and pipes hot again whenever you use a few gallons of HW in the sink.

During the winter, when the heating is on and the boiler and pipes are hot, it doesn't matter since any heat escaping will contribute to warming the house.

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