Hot Water - Settle An Argument Please!!

pappadruid

Hi All!

Im hoping someone can give me a definitive answer on this one! Basically, a friend of mine says that when heating hot water it is cheaper, and uses less gas, to leave your hot water on permanently rather than having it on a timer to come on twice a day for example. He says it uses more gas to heat the water from cold, whereas if the water is on permanently, the water is kept at a steady temperature which uses less gas to maintain that temperature. Can anyone shed any light on this??

Sorry if this has been asked before.

Looking forward to the replies on this one!

Thanks all!

Swipe

Why not ask your friend if he also leaves his kettle on permanently. Same principle, he is wrong.

Cardew

That question is asked several times a year about heating and/or Hot water.

It is amazing how many people like your friend believe the 'Urban Myth' that it is cheaper to leave it on 24/7.

Apart from the kettle analogy, let us take the case of you going away for a year.

Would you leave the water on 24/7 for the whole year "because it uses more gas to heat the water from cold"?

How about a month?, A week? A day? - all exacty the same principle.

Theis is a quote from the Energy Saving Trust.

Question

Is it more economical to leave my heating on 24hrs in the winter?

Answer

No. It is a common misconception that it is cheaper to leave your hot water and heating on all the time. Boilers use more power initially to heat water from cold, however the cost of this is greatly exceeded by the cost of keeping the boiler running all of the time.

The best solution is to programme your heating system so that it comes on when you need it most (possibly early morning and in the evening), and goes off when you don't need it (when you are out of the house or asleep). There are a range of controls that can be used and your heating engineer will be able to provide you with the most appropriate solution.

Depending on your circumstances it may be necessary to keep the heating on all day during winter but it will cost more than if you turn the heating off when you don't need it.

That said it doesn't cost a huge amount extra to leave your HW on 24/7 provided you have one of the modern foam lagged HW tanks.

These, filled with water at 65C, lose around 2kWh in 24 hours(they are tested to a British Standard). Given that they are always likely to have some warm water left in the tank, the actual difference between timed and 24/7 is probably around 1kWh to 1.5kWh a day - say 3p to 5p.

In any case that heat is not realy lost as it warms the fabric of the house.

Pincher

I was doing a coursework presentation for a first year Computer Science BSc, and said: "If you remember from your Physics "O" Level, ....." The audience reacted in a hostile manner, and jeered that I was being obnoxius and rude by assuming science undergrads had studied Physics.

That's why they drive 4X4s, because if they went to the shop without SatNav, they would get lost and die of dehydration.

Chrysalis

some boilers are dumb in that they have no sense if the water is already hot, like mine it does not turn off if water is boiling. So in my case leaving it on 24/7 would defenitly not save money and would actually be quite expensive.

Even if there is a thermostat simple logic suggests it will not be cheaper unless maybe you use hot water quite frequently in large quantities such as multiple baths spread throughout the day.

For me I go for large periods without having hot water heating on at all and simply use the kettle or wash with cold water, I only have hot water for baths or if its on anyway for central heating.

I expect the most efficient way is those new types of boilers where they turn themselves on by demand, so you turn the hot tap on and then the boiler kicks in then within a few seconds you have running hot water, the boiler immediatly turns off when the tap is stopped.