keep your immersion heating on all the time or only when needed?

kah22

It's an old chestnut I know but perhaps I'll give it another outing

So the question. Is it best to keep your immersion heater, or oil, on all the time and have hot water on demand?

Now here's my situation: I currently living alone and recently had my heating and plumbing upgraded. My hot water tank is completely encased in what appears to be cork, my boiler is a modern condensing boiler. The hot water and heating are separate.

As you'll appreciate living alone I don't really use gallons and gallons of hot water. Really all I use it for is washing the floor, general cleaning, rinsing cups, plates and the like and personal hygiene: shaving, washing face and hands - that sort of thing.

There seems to be three possibilities: leave the oil or electric on all the time and have hot water on demand Or only heat water as you need it. The third possibility would be use a kettle for all of the small you jobs eg washing, shaving, rinsing plates that sort of things

So oil or electric on all the time or only when you are going to use it?

globalds

if you heat a tank of water and don't use it for a bath ..how long does the tank stay hot enough to be usable after the immersion heater is turned off ?

I am thinking a timer for an hour two times a day might be better than leaving it all day.

CashStrapped

The insulation on the hot water tank is key to answering this question.

If the hot water tank is very well insulated then it should lose very little heat over the day.

Can the hot water be heated by both condensing boiler and the immersion? Or just one?

If both, the you have to decide which fuel is cheaper. I am not clued up on oil prices so that is somthing you have to work out yourself. What does the oil boiler cost to run per KWH?

If the hot water tank is electric only then you have to consider the following.

1. Most immersions have an adjustable thermostat inside them, so you can set it to the temperature you want.

2. Contrary to what most people think, once the hot water tank has reached the chosen temperature, the immersion turns off anyway.

3. If the hot water tank is well insulated, it should stay very hot all day. Therefore the immersion will not turn on very often, if at all.

4. The only time it will turn back on is when you use some hot water and it needs to re-heat and bring new cold water up to temperature.

5. If however the insulation on the tank is useless, it will lose a lot of heat and the immersion will keep on coming on to maintain temperature. In that instance you should only put the immersion on when you need it.

6. If the hot water tanks primary heating method is the oil boiler, then the immersion is only a backup. This means the immersion may only heat up a small percentage of the tank. So really you have to go back to the first question. How much is the cost of your oil boiler per KWH?

JJ_Egan

Personally i find the key is using the hot water .
Take a gallon out and its replaced by cold water likewise a couple of hours later and next morning you have a tank of cold water .

OP can easily measure cost via meter readings .

In a similar situation i boil a kettle on the gas for most minor jobs .Hot water via gas heat a tank about once a week .

PasturesNew

Only turn it on when you need it.

You don't keep turning the kettle on for 2 minutes every hour in case you want a coffee do you?

HappyMJ

kah22 wrote: »

It's an old chestnut I know but perhaps I'll give it another outing

So the question. Is it best to keep your immersion heater, or oil, on all the time and have hot water on demand?

Now here's my situation: I currently living alone and recently had my heating and plumbing upgraded. My hot water tank is completely encased in what appears to be cork, my boiler is a modern condensing boiler. The hot water and heating are separate.

As you'll appreciate living alone I don't really use gallons and gallons of hot water. Really all I use it for is washing the floor, general cleaning, rinsing cups, plates and the like and personal hygiene: shaving, washing face and hands - that sort of thing.

There seems to be three possibilities: leave the oil or electric on all the time and have hot water on demand Or only heat water as you need it. The third possibility would be use a kettle for all of the small you jobs eg washing, shaving, rinsing plates that sort of things

So oil or electric on all the time or only when you are going to use it?

I leave it on all the time. I want hot water to be available all the time.

It doesn't cost that much more as the cylinder is well insulated so as soon as I've filled the bath I can hear the boiler reheating the cylinder getting the water hot again ready for another bath if I need one.

Electric immersion cylinder's usually have two elements one at the bottom of the cylinder which is left on all the time and set at a higher temperature heating the whole cylinder at night at E7 rates and one at the top heating a small amount of water if the whole cylinder is used which should be enough to wash your hands and wash the dishes with. This water though is heated at expensive day rates so the thermostat is set lower than the bottom element so it rarely comes on.

Bigphil1474

When I were a kid, my dad had an electric immersion heater in a house where he had to put 50p in the meter every so often. He used to go ape if we left it on more than 30 minutes, but he always was a bit tight - gravy sandwiches anyone. Fortunately, I have gas heating/water and the water comes on for an hour in the morning and an hour in the evening, and we have hot water whenever we need it most of the time. Odd occasion it's not quite hot enough yet, I use an electric kettle to wash up. Perhaps an experiment is called for - let us know how you get on.

boatman

Use a dishwasher every 3 days and use electric shower, can fill the basin using that.

matelodave

As said above if your tank is well insulated it will lose around 2kwh a day when it's hot. So if you heat it all day it will cost you around 2kwh whereas a cooler tank will lose less heat (laws of physics) so letting it cool down overnight means it loses less heat. Also bear in mind that everytime the boiler kicks in it has to get hot and then circulate hot water between it and the tank, so the less frequently that it does it then less energy is wasted.

We heat our tank for around an hour and a half a day - just before we get up and it stays hot enough for a couple of showers pus any other ablutions during the day, water for washing up or cleaning and there's still enough hot water for a couple of showers the next morning (although the last one might be a bit short).

We only heat the tank to 45 degrees as well so we actually use most of the water in the tank as it doesn't need diluting with cold.

There's a flow restrictor on the shower and neither of us have long lingering showers so we don'y actually use a lot of hot water anyway - about 15-20 litres each.

Try it out yourself, just heat for an hour a day and see how well it lasts, if not enough add another half a hour or so until it does, perhaps in the evening if you like a bath before bedtime - bear in mind that 1 kwh of leccy is around 12-13p whereas 1kwh of oil is only about 5-6p a kw. You do the sums