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Original poster

Should water heating stay on all the time?

28 replies

Naz2009 · 05/11/2022 02:05

I've just moved into our new home and it has the old water tank system with air flow for heating. No central heater.
To have warm water there is a switch which says "warm water" should I keep this on all th time. Will this cost a lot as boiler is on all the time. I'm very confused by it all. Also is there setting to to turn water temp down?
I need help understanding this system.

OP posts:
Orangesare · 05/11/2022 05:02

If the water heating is via an electric immersion heater it will cost a fortune to leave it on all the time. Decide how much hot water you need and put it on a timer for twice a day

Orangesare · 05/11/2022 05:04

I’ve just read you have a boiler, set the boiler to heat the hot water two or three times
a day. If there is not a timer programmer get one fitted as it will save a significant amount of money

InterestQ · 05/11/2022 10:04

I have an immersion heater that I leave on all the time - I’m on E7 and I use 1kw of energy overnight even with the immersion on all night. Modern ones have a thermostat in so turn themselves on periodically so you have hot water on demand and the tank will be very well insulated but they reheat the water when it drops below a certain temp. It is quicker and uses less electricity to heat ‘quite hot’ water to ‘hot water’ then from cold to hot.

the expensive bit is reheating the water after a bath or shower. So if you use up all your hot water then the immersion element has to heat up the new cold water and that’s what costs a lot. I think mine uses up 4-5 kw after a bath.

PicaNewName · 05/11/2022 11:17

We have the immersion heater on a timer for 1 hr twice a day and it does make a difference to our electricity bill.

Sunshineandrainbow · 06/11/2022 06:46

I turn mine on overnight ever other night.
Just wondering though if I have a shower will the tank be then topped up with cold water reducing temp of the water in the tank?

Original poster
Naz2009 · 08/11/2022 06:41

Thank you for your guidance. I'm anxious about my bill now. As I had it on, all night and day for a good few days.
I've now turned water heating off and the hot water lasted around a day and half. So I will be only switching the water on for an hour in the day.
Luckily our shower is electrical. So I'm thinking it doesn't use the water tank water.

OP posts:
Dontfuckingsaycheese · 08/11/2022 06:47

Do you even need it on if you need an electric shower? Do you have a dishwasher? If so I’d be tempted to leave it off and just boil the kettle when you need hot. Unless you do a lot of hand-washing (hands/clothes/dishes) etc.

Orangesare · 08/11/2022 17:56

Yes when you use water from the tank it refills with cold.
I found it more expensive to have it on all the time than just a couple of hours a day.
As pp said if you have an electric shower and dishwater is there any point in using the immersion heater

Halstead · 08/11/2022 18:27

I have recently tried switching hot water from ‘on all day’ to ‘on for 1 hour a day’

The latter seems to be working out at £1 a month more expensive according to my gas bill (only using it for hot water currently, heating not on yet).

Original poster
Naz2009 · 09/11/2022 05:06

@Dontfuckingsaycheese @Orangesare I don't have a dishwasher and I have a baby and have endless bottles and pump to wash few times a day. Also all the other dishes and constants hands and face washes.

OP posts:
Original poster
Naz2009 · 09/11/2022 05:10

@Halstead I was speaking with my sister yesterday and she was saying to me "it will end up costing you more by switching it on for an hour rather than leaving it on all the time. When you on and off the boiler, it uses more power to switch on and costs more."

OP posts:
maudesvagina · 09/11/2022 05:17

We have a boiler and an immersion heater. The gas boiler heats our water on a timer so we don't ever need to turn the immersion heater on. Check if your boiler is heating your water - look at the panel on the front and maybe download the manual so you understand it better.

Orangesare · 09/11/2022 06:42

Twice a day for the boiler to heat the water is fine. My parents have there’s on 2 hours in the morning and two hours at teatime.

The boiler is the cheaper method of heating water and the immersion should be switched off.

The best way is to heat the tank up then test the on constantly for 24hours with a meter reading at the beginning and end and then test the on twice a day for 24 hours. Try and keep the useage the same

GasPanic · 09/11/2022 10:43

Halstead · 08/11/2022 18:27

I have recently tried switching hot water from ‘on all day’ to ‘on for 1 hour a day’

The latter seems to be working out at £1 a month more expensive according to my gas bill (only using it for hot water currently, heating not on yet).

I have seen info that says modern cylinders lose about 1 kWh a day, or 10p in gas terms (assuming 100% efficient heating). Older ones lose more maybe as high as 4 kWh per day. So if it was possible to remove all of that loss from a modern cylinder you are looking at 30 days x £0.10 per kWh = £3 a month, or £12 a month max with an older cylinder (the actual calculation is more complicated than this but it gives a rough idea of the possible maximum). There is probably quite a lot of heat loss as well from the pipes around the cylinder but I can't guess how much. I got some of that grey pipe insulation from Screwfix and insulated all the pipework in the airing cupboard that was hot to touch to reduce the heat leak.

In winter the "waste" heat from the hot water cyclinder isn't really wasted as the cylinder is just like a giant radiator and so it heats the airing cupboard/house. You can use the airing cupboard to dry off clothes or towels and save energy that way. In summer of course the extra heat is not wanted so better to try to stop it.

Where I started to find I saved money on water heating was only boiling 1 tank every 2 days. There was enough left over in the tank after the use on day 1 and it was hot enough not to need heating again and day 2 because the tank was so good at stopping heat loss. I think you need a cylinder of size about 50 litres x #people in house to do this.

Overall I would say that I agree there are not huge amounts of money to be saved by optimising hot water heating, especially if you have a modern cylinder. But if I had an older one that £12 would get me an extra 8 hours of CH per month for free if I could save the money.

Original poster
Naz2009 · 09/11/2022 19:27

This is my boiler/ heating system

Should water heating stay on all the time?
OP posts:
Original poster
Naz2009 · 09/11/2022 19:36

@GasPanic thank you so much for all that information, you have been very helpful.
This id my water tank and I like the idea of drying clothes there.

Should water heating stay on all the time?
OP posts:
AssignedSlytherinAtBirth · 09/11/2022 19:37

Just a note to say be careful about turning the temp down - when I asked our boiler guy about that he said it needs to be hot (I can't remember how hot) in order to kill the bugs and prevent Legionnaire's disease developping in the system.

Singleandproud · 09/11/2022 19:43

I don't have a water tank but I have an electric shower for washing and dishwasher so I just turn my boiler off weekdays, DD prefers a bath at the weekend so turn it on for that and that's about it. If I didn't have a dishwasher I'd probably use kettle water. It takes ALOT of energy (4,200 Joules per kilogram per degree Celsius) to heat up a water tank.

Singleandproud · 09/11/2022 19:52

Legionnaires bacteria is killed at 60 degrees C so getting the system up to that temperature and running the tap (or infrequently used shower or other water appliance) for a couple of minutes should reduce any risk of contracting that.

Original poster
Naz2009 · 09/11/2022 20:25

@AssignedSlytherinAtBirth that's worrying. @Singleandproud thanks for advice.
The water comes out hot whilst the hot water is switched on. I don't think I can actually control the temp of the water.
I do miss my combi boiler and central heating.

OP posts:
maudesvagina · 10/11/2022 10:08

Those little red bits on the circle control your timer not sure whether pushed towards the middle switches on or off but the manual will tell you if you hear the water via this you shouldn't need to turn your immersion heater on.

GasPanic · 10/11/2022 10:16

Singleandproud · 09/11/2022 19:43

I don't have a water tank but I have an electric shower for washing and dishwasher so I just turn my boiler off weekdays, DD prefers a bath at the weekend so turn it on for that and that's about it. If I didn't have a dishwasher I'd probably use kettle water. It takes ALOT of energy (4,200 Joules per kilogram per degree Celsius) to heat up a water tank.

This.

There was someone on another thread I think. Was much cheaper to boil the kettle to do the dishes than boil up a whole hot water tank.

So say you have your showers in the morning and do the dishes at night, I reckon it would be cheaper to boil up the water in the morning and use that, but then just boil the kettle for the small amount you need for the dishes.

Basically you only want to boil up a full tank of water if you are actually going to use it all.

nannybeach · 21/11/2022 10:54

Singleandproud, electricity is measured in kilowatts, not killagrammes

Singleandproud · 28/11/2022 07:23

@nannybeach
I was referring to the electrical energy required to heat a full water tank.
Joules is the unit of energy.
Degree C the unit of temperature.
The specific heat capacity is how much energy is required to heat 1 kg (1 litre) of a liquid by just 1 degree C. The specific heat capacity of water is 4,186 J/Kg /degree C.

So to heat a full water tank you would be putting in 4,186 Joules x however many litres of water in the tank x by how much you want to increase the temperature by. That is a lot of electrical energy. Which is why if you are just using hot water for washing up its better to boil a kettle and not heat the whole tank up.