If you have a fairly old boiler in your home, you may have a hot water tank too. The hot water tank stores the hot water as the boiler produces it, which you can then use as and when you need it.
On the face of it, storing large volumes of hot water is not particularly efficient, since if you don’t use it, it will quite quickly get cold. It is the same principle as boiling a kettle. The more water in the kettle, the more expensive it will be to boil it. There is no point boiling an entire kettle of hot water for one cup of tea, since the rest of the water will quickly cool down and therefore it will waste money.
The major advantage of this type of boiler (and hot water tank setup) over newer combi boilers (which produce hot water on demand), is that you can still get hot water even if the boiler breaks down.
>>> Should I replace my conventional boiler with a combi? <<<
If a combi boiler breaks down you will have no hot water – that is the bottom line! If you have a hot water tank, provided it has an immersion heater, you can still produce hot water even if the boiler breaks.
Immersion heaters mean you can still get hot water
On top of the hot water tank is an immersion heater. This is nothing to do with the boiler; instead it runs on electricity directly and essentially acts as a huge kettle. This means that even if the boiler is on the blink, you can turn on the immersion heater at the switch and still warm up enough water for a shower or bath.
Heating water with immersion heaters is expensive!
The problem is that heating water with electricity is about four times the price of heating it with gas; therefore it is not advisable unless absolutely necessary!
>>> Solar PV and Immersion heaters – a match made in heaven! <<<
Often, the two most costly electric items in the home are electric showers (which a few of you might find surprising) and the immersion heater.
If you can keep the immersion heater turned off unless absolutely needed then you are going to save yourself plenty of money.
How do I know if my electric immersion is on?
The first thing to do is follow the wire (where possible) from the immersion heater element at the top of the hot water tank to the wall, where hopefully you will see a switch. If it is on, flick it off!
If you can’t see any wires, then the process is a bit trickier. Since immersion heaters use a lot of electricity though, they normally get fed from a supply directly from your fuse box. You should be able to see a circuit breaker of fuse labelled ‘immersion’ – if this is on the on position, flicking this will stop power going to the unit.
Immersion elements are great for emergencies, but expensive for every day use
Obviously immersion heaters are great as backup – but we really suggest trying to heat water with the boiler where possible. If your boiler is on the blink, you may be happy that you are creating hot water as you need it with the immersion heater. You need to remember that the increased cost you will pay for the electricity would probably cover the cost of calling out a plumber to repair the boiler!
There are a few problems with the accuracy of this article, and I’ll address the principle two:
First of all, an electric shower is NOT expensive. On average a five-minute shower with a 10kW shower will cost under 11p. Indeed, it’s even possible to pay just under 8p for a five-minute shower with a typical 8.5 kW shower.
Secondly, electric immersion heaters are not necessarily expensive at all. We get a year’s hot water by daytime electric immersion for just £219 a year. This gives us four showers a day, plus hand-washing. It’s all about control. You should always put an immersion heater on a timer, and adjust the timer according to the time of year.
The ‘cheapness’ of our hot water costs show why hot water solar panels can actually cost you money, not save it – even when that water is heated by daytime electricity. We would NEVER retrieve the costs back from a hot water solar panel array!
I was advised by my plumber recently that the cheapest way of heating the water for me, living most of the time in a house on my own, is not to use the boiler but to keep the immersion heater on contstantly, as he said it takes very little electricity to keep it hot, and much more to heat it up from cold. This sounds different from your advice. Could you give me your reaction, please?
dione
Your plumber needs to do a course in Physics!
I have a very old boiler and emersion heater. When I switch boiler off in summer, I then just switch emersion on. This year so far I have only put emersion on when needed. However, my Bill I have just received says I’ve used more electricity so far this year according to last year. I live my myself and now not sure if I shouldn’t keep switching emersion on and off, but leave it on all the time. There’s so much conflicting advice.
I have a old boiler which really needs replacing and I have all but given up on it.I live by myself and I will not be turning on gas heating this year.I am thinking of turning of the gas to save the standing xharge.Will I save money and how long does it take to heat he water?
i do not have a boiler just an emersion heater
Hi Dione,
So we would definitely not advise leaving your immersion heater on 24/7. This is because it is heating your water using kWh priced at around 13p. Whereas if you used your boiler it would be around 3-4p. Immersion heaters should only really be used when the boiler is not working, or you need an urgent boost due to high usage. For maximum efficiency make sure you have a cylinder thermostat so the water isn’t being heated beyond the required temperature.
There is one more fact that has been omitted in these discussions. Whereas gas for central heating is indeed about a quarter of the cost of electricity, in a condenser boiler, the water heating is not as efficient as the central heating. Hot water is produced at around 55% efficiency compared with around 89% for C/H. If this is true, then an immersion heater will cost only around twice as much as gas.
Gas still has the edge cost-wise, of course, but not by so much and the convenience of a hot water cylinder is,as explained worth the extra if used as a top=up for hot water in the cylinder.
Alan,
No my point did not include heat loss from the pipework from heating to tank. I was informed by my boiler installer that when the system calls for hot water to be produced, the water heating process by-passes the condenser. Now I have tried to contact Vaillant – which produced my boiler, for confirmation – or otherwise – of this comment: so far without an answer.
Mark,
You make an interesting point. Do you have anything to back up the 55% efficiency assertion? I am assuming you are referring to the loss of heat from the pipework from heating to the tank? I find it hard to believe that you will get a 35% drop in efficiency just by transferring the water to the tank. Any losses from storage in the tank will be the same if heated by the immersion or the gas, so it would only be heat lost during transport that you are referring to?
would be crazy leaving immersion heater on all day. Just use your boiler, make sure you have a timer as well as a cylinder thermostat though. And don’t forget the insulation.
what if you do not have a boiler only an immersion water tank. Would you leave it on 24/7 or when would you put it on?
Dione,
Absolutely make sure the tank is well insulated – that is a good point. Never, ever leave your immersion on. Not only is it more expensive per unit, but it will just keep boiling away all night costing you a fortune. I have seen people who have made this mistake spend a thousand pounds on electricity in a quarter!
This is really useful. We quite often switched on our immersion to heat up the water, but will now use the boiler going forward. Anything to save a few quid!
I have a 125 litre Heatrae Sadia Megaflo immersion tank in my one bedroom flat.
My electrician fed the electrical supply from the element into a basic timer (Fused spur timeswitch) by TimeGuard.
I am on economy 7 with OVO at approx 6p kwh night, 12p day and have my immersion on for 1 hour at 4am in the morning which allows me and my wife 2 medium length showers each per day, sometimes I use the one hour boost.
Great system and efficient as it can be with a timer on it
With regard to Barrys comments on underfloor heating I will cover that on the other blog.
Hello Jon
May I ask how many kwh it takes to heat your 125 litre tank? I’m just about to move in to a flat that only has electricity and am worried about the energy costs.
I appreciate your time.
Nikky
Hi Nikky, it depends on the starting temp of the cold water and the end temperature you are looking to achieve. Normally the immersion units are 3kW, so the formula is
Volume of tank x 4 x temperature rise / 3412
So it would be 125 x 4 x 50 / 3412 (where 50 is the temperature you want to raise the water by and 4 & 3412 are constants)
This is 7.3kW required – which with a 3kW immersion would take just over two hours to heat fully. Electricity is 14p / kWh, so per hour it would cost 42p to run therefore you are looking at about 80p.
Obviously the key is to really well insulate the tank and then you don’t need to worry so much, because the temperature you will need to raise the water by will never be 50 degrees because the water in the tank will still be warm.
Hi James, I have a client with a 250ltr pressurised hot water cylinder, top and bottom element fed from direct mains only,only two people in the house,they switch the bottom immersion off only using the top one which is always left on, there is no programmer fitted, is this the most economical method? Should they fit a programmer to top immersion or top and bottom or what would be best?
This is a really useful article. We had exactly this problem with our immersion heater. Told the kids to use in case of emergencies and then as soon as the shower got cold they would flick it on and then forget they had done it. This has happened about 10 times now so need to find a way to stop it!!
Tina
Hi Tina,
Thanks for your comment. I see so many properties where the immersion is left on and forgotten about – it is like pouring money down the drain. You shouldn’t really need to turn it on unless the boiler packs up, it just takes a little bit of discipline timing your showers – always a problem with kids!
Hi.
We have just bought our first home and the set up is very old (we bought it from an old lady who lived there for 39 years!)
It is all electric and there is no gas supply in the street.
We have night storage heaters and a hot water tank/immersion heater, but no boiler.
The shower is electric so heats up itself, but what settings would you recommend for us to use please? eg timer,temperature etc
There are only 2 of us so just need hot water for hand/face washing and doing the dishes etc.
Many thanks
hi i have the exact same situation and would like to hear the advice given
Hi Chris, congratulations on the new home! In terms of this set up, it is quite common, so the first thing is the storage heaters – these charge during the night on ‘cheap’ electricity and then emit the heat during the day. The first thing to check (if you want to keep the storage heaters) is that you are on an Economy 7 tariff – that gives you access to the cheaper electricity. Provided you are, you need to charge them during the hours that the electricity is cheap. You then control the heat output, so normally people will try and coincide this with when you come home from work (ideally just before so the home has a bit of time to warm up). In terms of hot water, provided the hot water tank is insulated, you should be okay using the immersion for one hour a day. You might prefer 30 mins in the morning (so it is warm when you wake up) and then an hour about 4 (to coincide with coming home). If you are at home during the day, storage heaters can be very expensive since electricity is more expensive than gas to heat the home, so if this is the case you might want to consider the switch. Let us know how you get on!!
Don’t forget to check the clock on your Electricity meter to make sure it is switching to cheap rate when you wish to use the most power for heating of home (night storage rads) or Emersion (tanked water). Sometimes these clocks wander (with respect to the correct time, especially if you have an old meter), depending upon the degree of inaccuracy you may want to report this to get it corrected (or not if it suits you better!).
Surely immersion heaters are awful aren’t they? They are just like a massive kettle. I get having one for backup, but would never normally use it!
Hi Simon, thanks for your comment!
In our opinion electric immersion heaters aren’t great to be honest – as you say only to be used as a backup!
Hi I have a immersion heater and boiler but it’s not a combi boiler do I need my immersion heater on all the time to get hot water
Hello again, Alan
Have just received a reply to the question `Does the efficiency reduce for water heating?` from Vaillant; as follows:
Generally the answer is yes, it is all to do with the return temperature when using external 230V controls and the boiler maximum flow temperature is set to 75°. If the return was to come back at 55° it would be condensing but when it gets closer to the maximum it will stop condensing, this is when there is a benefit in using Vaillant controls you can range rate the cylinder kW output, maximum temperature and cylinder offset which will keep the boiler condensing for longer.
Hello, I wonder if you can help. My parents have no boiler/central heating. They have an immersion for hot water. They definitely need central heating putting in, would they be able to qualify for any of the free boiler offers? Would be grateful for any advice.
Hi! Please help! I live in an old house! In the Summer we have lovely hot showers but in the Winter when the heating is on the showers are Luke warm! I have to manually turn the boiler on as the control panel has broken so I am therefore unable to set it to come on early in the morning. Would it be more cost efficient to leave the boiler on all night (but turn the heating off) or put the emmersion heater on when I go to bed. To have the boiler and the heating on at the same time doesn’t heat the water efficiently. Thank you!
Pls help my immersion water heater switch won’t switch off it remain on with the light on in both the on and off position . I have to switch it off from the circuit breaker . How can I correct this does it have to do with the thermostat on top of the immersion element , if so what should I do to correct it thanks
Marcia the light you are referring to on the switch on the wall adjacent to the immersion heater, if it is then it sounds as though your switchfuse is faulty and will need replacing. I would suggest you contact a competent electrician to get it tested and if necessary replaced.
The Fused Spur may be incorrectly wired in backwards with switched O/P being used as the I/P from the mains (the Neon is normally placed across the switched O/P so it only comes on when the switch is on !), Thus the Neon will be on all the time irrespective of the switch position.
Hi
Good post with logically flown thoughts on using immersion heater!
I have 2 kw solar panels and with the summer setting in I will have output from them more enough to run other devices probably another immersion heating tank itself! Now we have switching devices in the market that can manage the excess power. I saw solarimmersion in my friend’s neighbour’s home. Does anyone have it and how is it performing?
You will need something like what John below is using. if the solar pv is only generating 200W in excess of what the house is using, then turning on a 3kW immersion heater will result in pulling 2.8kW from the mains. Since the o/p from Solar PV alters over time (Shade, Clouds etc) the exported energy has to be continously measured in order to work out how much power can be fired into the immersion. This is normally measured and switched much faster than the individual half cycle length of the mains supply which is 10mS, so we are talking around every 125uS! Power is switched for a fraction of a half cycle at a time in order to manage a 3kW load!!
Hi Richard,
I too have 2kW of solar panels and had them for over three years now. It has always annoyed me that most of the kW’s generated during the longer summer days are just exported to the grid unless using electrical appliances during the day. I recently came across articles about automatic switching devices. Recently I purchased a ‘Solar iBoost’ that is wired between your immersion heater switch isolater and immersion heater. There is a wireless transmitter fitted adjacent to your electric meter that sends information to the Solar iBoost. It then switches on the immersion whenever the generated solar power is over 200watts, so all excess power goes to the immersion. It is great, even on a resonable sunnny day I get a tank full of hot water. I still leave on my hot water cycle on the gas fired boiler, but this now comes on early morning but as most days the tank is hot from the previous days solar input, it rarely stays on for long.
My one bedroom flat only has an immersion heater, no boiler. I work full time Monday to Friday and only need hot water for a couple of hours after work each day (6-8pm). I had it on for two weeks straight without realising the potential cost so have now turned it off and will only switch it on for a couple of hours when I get home each night so I can wash etc. is this the most cost effective way?
Another query which is linked to the above is that my flat has storage heaters which i think must run from the immersion heater? If so is there no way of having the flat warm when u get home without leaving the immersion on all day? I get such mixed opinions from people it’s crazy. I don’t like coming home to a cold flat and having to wait for the water to warm up but at the same time I can’t afford to leave it on all day!
Thanks in advance.
Hi Giles, a couple of interesting points there.
From what I can tell, you have an immersion heater to produce your hot water and then storage heaters to provide your heating. These are completely unrelated – the storage heaters get ‘charged’ with electricity – they normally work with the Economy 7 tariff, where the rate you buy electricity at night is cheaper than the rate you pay during the day. They charge during this cheap period – and the electricity is used to heat bricks and the theory is that this heat is retained until it is needed within the heater – hence the output dial on the storage heater, this sets the rate at which the heaters give up their heat once charged. The main issue with the older storage heaters is that by the time you want the heat, it tends to have leaked out, which means you need to recharge them.
In terms of the immersion, again this runs off electricity. Based on the fact you are on economy 7 (am I assuming that based on the storage heaters), you should definitely heat the hot water during the night – maybe from 4am – 6am. This means that it will cost less to charge because the electricity is cheaper. This should provide all the hot water you need for the day to be honest (if the hot water tank is in anyway insulated). If you then need more hot water, just flick the immersion on for an hour or so.
Hi, I just moved into a property and amount of electricity my boiler is consuming is huge. Am spending about 10 pounds a day. Is there any way you can help me to save a bit. Thanks
Hi Paul,
It sounds like you immersion is on 24/7. This is not a great idea! Find the plug for the immersion and switch it off! You only need this on for an hour or so to heat a full tank of water. Keeping it on all the time is like continuously boiling a kettle.
After that you are going to need to give us a bit more detail – electric boilers are very unusual. You normally get gas boilers with hot water tanks that have electric immersion backup. If you have no electricity in your home then yes – the immersion is going to be producing your hot water but ideally this should be put on a timer so it comes on for just a couple of hours a day to help minimise your energy bills!
Even a well insulated foam encapsulated hot water cyinder can lose about 2 units (2 KWH) of electricity per day, often referred to as ‘standing loss’. The tank our builder put into our new house about 10 years ago only seems to be very poor only having about 25 mm of insulation on it and the inside of our airing cupboard was always very warm. For about £15 I have cut the hot water heating costs considerably. Firstly I have covered all the hot pipes with foam pipe insuation (cut with a sharp kitchen knife and mitre the corners on pipe bends for a neat job) occasionaly held in place with insulation tape. I then bought a 75 mm tie on foam jacket from screwfix – it is in six panels so that you can allow for pipes. Do NOT cover the immersion heater but take the insulation round it. So my tank now has 100 mm insulation and now only a warm, but not hot airing cuboard.
As a long since retired gas engineer, I’m not sure I entirely agree with some of the replies.
Of course the immersion should be controlled by a time switch, but leaving it on all day, or even all night to, won’t cost the absolute fortune digested. A well insulated storage tank will loose about 2kw per day, or about 30p although perhaps poor plumbing might increase this. Then there is the question of thermostat settings. Current advice is to keep the setting low, to reduce the afore 2kw heat loss, BUT and its a big but, if you find yourself washing under a running tap, or running the tap for long periods waiting for the water to become hot, that’s not actually cold water that’s going down the drain, but hot water that has gone cold, and it’s being replaced with cold water at the cylinder, which you will now have to heat. My advice would be to set the thermostat so that the water is actually a little too hot. That way you can start to collect the initially cold water, knowing that the following hot water will bring it up to the temperature you actually want.
And one final point. When comparing relative costs, I assume we are talking about town gas because LPG is considerably more expensive.
Hi I have recently put my electricity metre readings into my energy account and had a massive shock with the amount I have been charged for my electricity. I live in a rented flat and there is no boiler only an immersion heater. We had it on continuously for six months without knowing how much it costs.
I have read the information provided here and I understand putting a timer on the heater, is there a timer already fitted to the heater or do I have to purchase on? The immersion heater is not plugged into a socket, there is just a switch like a light switch so can’t add a timer plug. Also how long does the water in the tank stay hot for if I let it heat up for an hour or so?
Hello everyone,
Me, and a couple with an 8 months baby have just moved into a property which has both boiler and immersion. Also, the master bedroom is en suite and the shower has a pump which gives a really good flow of water.
The problem is when we use the boiler to heat up water, hot water is available everywhere else, but not so in the en suite. what could be the problem here?
The second issue is that in order for the central heating to operate, we have to switch on the hot water as well. Does this make any sense, because in all other properties i have been the hot water and central heating were operating independently.
I look forward for your comments. Thanks a lot.
Jay
Hi, my flat which is privately rented has an electric immersion heater only as no gas supply. The pipe (overflow?) which leads outside the flat seems to be leaking since I turned the water off to have a washing machine installed as had the wrong stop connector!!
How do I get this sorted please or will I have to call out a plumber?
Thank you.
Hi I have an immersion tank don’t know much about them ,the switch is on and you only get a quarter of bath full of hot water however it is a small tank but does not sound or fell like water or much is in the tank itself what could be the issue ?
Our rented house has a hot water tank with an immersion heater..We have no gas in the house. There is a back boiler connected to the old solid fuel Rayburn range, which .provides hot water when the stove is lit in Winter. We do not use the stove the rest of the year. Is there any way we can reduce the price of our hot water?
Hi, Am looking at moving into a flat with an immersion heater (no gas) and what I thought would be a storage heater but now believe it is not storage and economy 7 would not be useful. In fact E7 is not installed. What is the best way to use these? There is a shower but don’t know if it is hot water heated on the fly or comes from tank. Thanks.
Hi we just moved into a new property and were told that the heating was an immersion heater and gas central heating, we have a tank for the hot water and I boiler which I have never heard working,
The problem we have is, the hot water must be set to the same time as the heating, how do we know if it’s gas or electric Emerson supplying the heating? Would we need to request a Plummer to come and look at it?
Any help would be good.
It is so annoying that everything in my flat is electric including the immersion to heat hot water. If I use one hour of heating the water I have used £3.00 on the electric each day and for someone who is on low income is finding it hard to use this immersion.
Hi David, have you tried insulating your tank? In addition you need to put your immersion on a timer – a 3kW immersion element will cost about 40p to run each hour and 1 hour should be sufficient to heat a cold tank up to temperature. I would therefore suggest running this just for an hour in the morning and an hour in the evening – bringing the cost down to just 80p. Getting a basic timer on the immersion would allow you to set this up rather than having it running all day (unless you are happy to do this manually).
Hi James I need your expertise.
I need to replace old immersion heater and I have a choice : either a 210l pressurised tank for all hot water needs or a 90l pressurised tank for sinks and an electric shower.
The flat is a short holiday let. Some days 4 people , some 2ppl, some none.
What would be the cheapest way to install ?
I only have an immersion heater, no boiler. So I use it to provide my hot water for baths and hand washing. We have an electric shower so this works independently. Our immersion is thermostatically controlled so it will never boil all night. When it reaches its temperature it turns off. I have recently fitted a timer but I’m not convinced letting it get cold then heating it back up is very efficient. I’m thinking, if the tank is well insulated, I may as well leave it on so it can come on for a few minutes an hour to keep it at temperature. My three bedroom house is very old with solid brick walls so not particularly well insulated, we have electric rads and a large electric underfloor heating system and our bills are never more than £150pm. I also don’t have servicing costs. I think I’m certainly better off than my friends on oil.
I am adding solar panels, giving me free electric in the day. I have a standard gas boiler and an insulated HW cylinder with top immersion heater. I prefer a combi boiler, but plumber has said the standard is more efficient to run underfloor heating, and if I get a new cylinder with bottom immersion, I can heat water free in the day. I think this is a waste, and am thinking of localised hw heaters at sink and shower. Is this a good idea? If I keep the existing inefficient cylinder and boiler, both only 4 years old, then I have saved a lot of money in new equipment.
I put my immersion on last nite as ran out of credit on my metre 3 hours later the water is freezing anything i could check myself before I call someone
Hi Kelly, Do you mean you ran out of gas credit? The immersion should produce a tank full of hot water in 1-2 hours depending on the size of the tank and how big the immersion unit was.
Yeah, it was on for 3 hours still no hot water gave up in the end, I’ve got a tribune tank solar panels connected to it
My son lives in a rented flat with night storage heaters and an immersion heater, he is a single lad out at work all day but with everything being electric his bills are very high, he has a shower which required the immersion heater to be put on every time, would an electric shower installed be cheaper to run
Hi.. ive just moved into a property with a dimplex electric panel heating system and an electric immersion heater. It has a timer on it but i have no idea how to use it.. it only has 1 dial you can turn… so confused please help
How can i tell what time my emersion comes on
The switch is on if it is in at the bottom. The heater is on if the light on the switch is on. The heater is on if there is a noise coming from the tank. There is also an expansion pipe because as water heats up it expands and needs to be returned to the cold water tank. if you feel this pipe it will give you a good indication as to how hot the water is.
There is either a switch (which when you turn on turns the immersion on) or they are sometimes on a timer – if this is the case there should be clock somewhere near the immersion unit that you can then use to dictate when the immersion heater comes on.
Hi. I have just moved into a property which only has electric. The water tank has two switches ‘top immersion’ and ‘bottom immersion’ the lettings agency turned the top on and left it on, but i was a little worried leaving either switch on will incur high costs. There is no timer so I can’t put the hot water on a timer so I have been turning the switch on and off which is very annoying. Is this necessary or is there another way?
This tends to be for when you are on an Economy 7 meter – i.e. you pay two different rates for your electricity. A cheaper night time rate (approx 6-7p / kWh) then a more expensive day rate – 15-17p / kWh.
What happens is that the two immersion elements are using the two different rates. In an ideal world, you are heating the water using the cheaper ‘night time rate’ electricity. You then leave the day time immersion off and use it purely as a boost function if you happen to use all the hot water in your tank before the next evening.
Despite being switched on all the time, the immersion units have thermostats to ensure that they don’t heat the water to an excessive temperature, so you shouldn’t be paying too much for it to be on, although you may wish to insulate the tank further to minimise heat loss if possible.
Can you tell me, please, if it is possible to have a short top immersion heater in the hot-water tank, to heat a small amount of water for washing up and hand-washing, and a bottom immersion heater to switch on, only when wanting to fill the bath? This would would save having to heat the whole of the tank of water, when only a small amount of water is needed.
Hi Susan, sadly I can’t answer your question directly however if you’re looking to save resources (protect the environment) or save money then why not just boil the kettle for the washing up and wash your hands in cold water? Waiting for warm/hot water to arrive at your taps from the tank wastes a lot of water and don’t forget that the ‘cold’ water you’re wasting is being replaced by cold water into the tank reducing the tank water temperature and requiring more electricity to heat it up – it’s not just the warm water that is replaced 🙂 (Of course if you’re talking about hand-washing clothes then just use a kettle again).
Yes
I have just moved to rented accommodation and have and electric immersion boiler. It has two switches both commented to roughly the middle of the water tank. How do I know which switch does what?
Hi, we have just bought a house which runs from Immersion hot water and economy 7 storage heaters only. We are unsure how the immersion is controlled but we are definitely on the economy 7 night / day rates for the house.
there is a single on off switch about mid way up the hot water tank upstairs. should this be left on or turned on and off as required?
ALso down in the kitchen there appears to be two further controls and we are not sure which if any we should be using and how.
one has switch options (almost looks like light switches) these are labelled on / off (should this one be left on all the time or as and when required?), and to its right another labelled sink / bath.
Then above this, there is another control this time labelled economy 7 (looks pretty 1980s vintage) with a dial for summer/ winter and timer, an on / off button and a boost 1 hour dial..
Which switches should we be using, and which should be left alone?
any help would be much appreciated we are so confused Thanks
how long would a 210 litre megaflow take to heat up using an immersion switch?
This depends on a few things – firstly the size of the immersion element (typically 3kw in megaflo). It also depends on the temperature you want to heat the water too – but typically we recommend between 50 degrees and 65 degrees although Legionella is killed at 60, so ideally you heat it up to that temperature every so often even if you normally heat it only to 50 degrees centigrade. The last thing is the starting temperature, becuase obviously the higher the starting temp the quicker it will heat up. In this example lets use a starting temp of 20 degrees (so roughly room temperature) and heat to 60 degrees, using the 3kw immersion. This would take about 3 and a half hours to heat up – and would use about 10.25kWh of electricity, which at 12 pence per unit would cost £1.23. Hope that helps!
If I switch on the I ersion heater at night economy 7 and turn it off in the morning will it be cheaper rate?
Hi Groom, The Economy 7 cheaper rate period typically falls at somepoint between 10pm and 8.30am, but that period can vary across the country. i.e it could be from 11pm until 6am. You need to check with your energy supplier – but provided you are turning on the immersion during these hours then you shouldn’t have a problem. When people are on economy 7, they often have two immersion elements linked through into the hot water tank – one which is for the cheaper night time tariff and the other which is for the evening tariff, in which case provided the ‘cheaper tariff’ immersion is on, you should never pay a premium rate for producing hot water.
I have just come across this. We have a 120l tank with an immersion heater. I have left it on for the last month. Our electricity was probably £5 a month more than with it off, It is hard to say accurately at this moment as we have a oil fired boiler for heating and of course that uses electricity as well. So far I have found that the immersion is miles cheaper than gas for heating water. And even more cost effective than using the boiler for hot water via the heating system as with ours you have to have the heating on to get hot water .
Hi. I have been using the top ‘element’ in my immersion heater for several years now. The bottom ‘element’ which I understand is the economy 7 one was switched off due to a problem which I now think was because it was on a timer set outside the economy 7 hours when no electricity was coming through! The top element is on a timer for one hour in morning abd one hour at night which generally suits my needs for showers, washing up etc. A bath will take 2.5 hours of heating and doesn’t produce a full bath. What I am curious about is whether my top element is in fact heating the whole tank or just the top half and so I will never get as much hot water as if the bottom was heating up over night, coming on via Economy 7? This may seem a daft question!
Hi Louise,
It is unusual to ever get a whole tank of hot water – basically the element heats the water regardless of where it enters the tank and the hot water floats to the top of the tank. When you run the tap, this hot water travels to the tap from the top of the tank and cold water replaces it at the bottom of the tank. So basically it is irrelevant where the elements enter the tank!
But importantly it is worth heating the hot water tank on the cheaper evening tariff if you are on economy 7, and a jacket is certainly worth investing in to try to limit heat loss through the cylinder itself.
hi, i live in a 3 bedroom bungalow with just my wife, we have a gas boiler and a emersion heater we do not use the central heating as it is too expensive so we use a portable convection heater in the room we are using at the time. my question is this if i cancell my gas and turn on my emersion heater on a timer would i save money, everything in my bungalow is on electric i only need gas for hot water. thank you paul
Wow, don’t do that! Heating with gas will be far cheaper than heating with electricity. Just turn down the radiators in the rooms you aren’t using. Similarly to think of deliberately using an immersion heater for everyday hot water when you have a gas boiler is nuts, it will be far more expensive.
Is it cheaper to keep an immersion heater on all the time or to switch it on say once a day for a few hours?
Thank you for your informative article about immersion heaters, which dispels the common misconception that it is cheaper to leave them switched on. My wife and I live in rented accommodation and have no boiler but just a standard copper tank with immersion heater which is poorly lagged and quite old. The immersion heater seems to pack in every year or so requiring replacement and is inefficient because, as we don’t have a bath, we are heating a huge amount of water, just for hand washing and dishes for two people. I would think the solution would be to have a high power electric water heater fitted over the kitchen sink which would be used for both hand washing and dishes. I would value you opinion in the matter.
Regards
Chris
Hi. You say more than once “Keeping it on all the time is like continuously boiling a kettle”. But it isn’t. The power isn’t continuous. The thermostat keeps the electricity at a trickle feed effectively.
Also, if the cylinder isn’t against an outside wall, the heat loss to the air isn’t all lost, in winter at least, as it is contributing to heating the house/flat.
I’ve only got an immersion heater on economy seven. Am I better off leaving it on constantly or turning it off which means each time I turn it on it has to reheat the whole tank? I’m in a rented flat so have no other options?
Hi,
So I have a Emerson storage heater thats on eco 7, in a studio flat. Recently had a new kitchen fitted and they had to drain the system to fit the pipe work in the kitchen and since then it hasn’t worked. It used to come on at night heat up, so be hottest in the morning and cooler at night. Now just always cold. Woke up as I know when it’s on and the light to say it is on, wasn’t on, so changed the fuse in that still nothing any suggestions?
If I have a solar optimiser can I keep my immersion heater on permanently?
I’ve moved into a rented bungalow, no gas, electric wall heaters and an electric boiler in attic (immersion I assume). There are solar panels to reduce the elec costs – although the landlord keeps the money from elec returned to the grid. The boiler is in the attic. I found zero hot water until I pressed the boost button & wait 1-2 hrs – even then only 2 kitchen sinks full at 41dC max. I have arthritis and get muscle spasms and a bath for me is essential to manage/reduce the latter. I’m now a month in without this & on stronger pain meds etc – annoying! t Persuaded landlord to fit a basic timer switch as coming home & waiting 2 hrs seemed unreasonable. Now set to come on 2hrs am AND 2 hrs in pm. Progress, although I work shifts with an irregular pattern so need to keep adjusting timer isn’t ideal
Key issue – unlike what I’m reading, the water isn’t remaining hot or even warm by midday (timer am: 6-8am) I get cold water to wash hands, not ideal for achy wrists AND still only 2 basins full of hot water (41dC) after 2hrs def not a tank full. Plumber says tank set to 60dC and says boiler is pulling 10a instead of 13a.. I’m getting a bit desperate as impacting health & constant electrician plumber visits.
**will def check pipe & tank insulation”” IDEAS Please?! Wondered re Hive active plug to make faff of changing times easier but doesn’t help with piddly amount of hot water/temp not that high? Massive thanks in advance 🙂
I have had to turn my whole heating system off as the radiators are stuck on (even tho the heating is turned off) and are pumping out heat every time the hot water is on and we’re in the height of summer. So I’m now using my emersion and manually turning it on and off as it has no timer option. My question is, how long do you think i should leave the emersion on to heat the tank sufficiently for the day? The tank is 4.5’ tall and about 25” in depth. It is lagged but only with a thin 1” tight fitting cover.
Fix your mid position valve newer ones have a manual bypass as a short term solution.. About 70 quid. The immersion stat will mean it’s not on permanently unless you use it or you have rapid loss from a poorly insulated tank.
No one has mentioned using a combination of an immersion and gas in a well insulated system. I have a fully vented system with a gas boiler. The heating is TADO controlled with smart TRVs a Central Thermostat and Boiler controller. it geolocates my phone and sets heating patterns accordingly with a frost cycle and summer maintenance cycle. I have a magnetic filter. I have a timeguard smart immersion controller. My tank is well insulated as is my house. in summer my tank loses about 25 percent temperature in 2 days without heating. So in summer my immersion tops up the hot water over night for 30 minutes. I have never ran out of hot water. Using a 27 inch 3kw heater. people forget that the immersion has its own thermostat so on 24/7 is not accurate as electronic stats have an upper and lower tolerance unlike a bimetallic thermostat this means water can be kept within a range and therefore the heater is off most of the time. Not running the gas in summer except on a short daily cycle and having no loss through central heating in summer saves me about 20 percent on my gas bill which has a higher standing charge than electricity. Water heating solar on a single panel costing 500 plus 300 inastallation haa reduced my uncles summer water heating costs to 4 pence a month. I live on my own so having an automated system cost me 500 to self install. The trvs are 60 pounds each. The boiler control and Stat were 199 and the immersion controller was 70. In 8 months it has saved me about 30 per cent on gas compared to last year even with tariff increases. it. Might not work for everyone but it made my system a lot more efficient overnight. My house is always warm in winter with the added gimmick that I can control it with Alexa.
Hi Nick…your combination electric and gas systems sounds interesting. I was visualising of adding 5 cheap solar panels (say 1KW in total) to a 1KW immersion heater which attaches to the hot water tank. I have no background in heating and realise it can get quite complex. I guess I would need 5 solar panels, an inverter, one immersion heater, some way of connecting it to the water tank and some kind of controller. Not planning to use solar for anything else. Do you know what products I can use (like brand, product name).
Hi all,
Immersion heater has stopped working all together and it’s looking like we’re going to have to get another one installed. Found this article, https://www.priceyourjob.co.uk/immersion-heating-installation-cost/, which suggests it’s not an expensive job., labour-wise but was wondering if any of you guys could let us know if these figures were about right or if they’re a way off.
thanks, Sharon
The intelligent controller gets to work whether or not you’re in the house, meaning you automatically get hot water with electricity you would otherwise be exporting.
Our Coid water tank in the loft leaking do l need one to feed the immersion heater or can you feeditdirectly from the mains
Hi we have a conventional boiler and since putting the heating on we’ve noticed the water temperature isn’t as hot for a warm bath. The only difference this year to last is we noticed the plumber had left the hot water cylinder immersion heater on so we turned it off. British Gas repaired our boiler and the engineer turned the boiler heat setting down. Which do you think has caused the water not to be hot enough – the immersion heater being switched off or the boiler being turned down? The boiler is on heat setting 4 from 6. Without the heating on the hot water is perfectly hot enough to have a warm bath.
Is there a thermostat on the hot water tank? If so, try turning this up!
Hi I had 2 new elements put on my immersion heater last February and my bills are so high and the water is constantly hot.( thought it was because the elements kept it hot ) the booster switch off and I haven’t used it all year. Why is the water constantly hot and my bills so high ( 3 times as much) 🙁
Please advise. I have emailed the company who fit them but No reply as of yet.
Have a Immersion Heater with a timer, but would like to move timer so thats its higher on the wall (at moment its at ground level) can this be done by adding either a fused spur or a junction box to allow for the cable to be extended
I have a combi boiler installed.It is excellent for hot water but I can’t get hot water in my bath and I wondered if I should invest in an immersion heater for my baths only
i have just has an airsource punp installed should i keep the immersion heater on all the time ? thanks
If you have a combi boiler which breaks down (not happened yet thank goodness) and you have an electric shower you will always have hot water from the shower just not from the taps. We have one shower as electric and another fee from the boiler for that reason. Another bonus is that both showers can be used at the same time without loss of water pressure.
Hi
My electrician turned my immersion heater on to test it. He forgot and left it on. I didn’t know it was on until almost 2 weeks later. He has offered £45 to cover the cost. I have no idea (no smart meter) if this will cover it. He says because it’s not my primary hot water source it wouldn’t have been actively hearing very much. I only have the boiler heating water 2-3 times a week for 20mins at a time, so I think the immersion heater will still have been heating quite a bit. How do I calculate how much it has cost me? I can’t even rely on typical bill usage as too recently moved in. My electricity costs 21.22p per kWh, my tank is 114ltrs set at 60degC. I’d really appreciate some help please.
I wonder if the differential changes in summer when the Central heating is off. The boiler has to heat up from scratch whereas in winter it is already on. I use gas and 25 mins early each morning gives enough hot water for two showers and incidental bits of washing. According to my smart meter that is 3,78 kWh and costing 54p at the new inflated gas prices as of June 2022, Also does the heat exchanger heat the water more or less efficiently than a direct heating element as with the immersion?
If there’s an electrian/plumber on this forum, can you help or advise me what is the problem please?
We have air source as there is no gas here, the tank is in airing cupboard & has an immersion in it aswell. I have been switching the air source off after the water becomes hot enough to use because it is very expensive to leave on 24/7. The big problem we have is with the immersion, I tried using it when air sourse is off to see the difference with costs & it didn’t heat the water up. The immersion when switched on is suppose to boil hotter once a week to stop us from getting legionnaires disease. As we haven’t been getting any hot water through the immersion, do you think the immersion is not wired in properly or it is broken?
Is one hr day rate cheaper than leaving emersion heater on 7hrs night rate?
My boiler is off and doesn’t work, but I have an immersion heater, will my pipes be saved with this cold weather.
My boiler is off and doesn’t work, but I have an immersion heater, will my pipes be saved with this cold weather.
Very interesting reading on this forum. I have a slightly different question. I have a new Ideal boiler and also a hot water cylinder with an immersion heater. I turned off the immersion heater but sometimes when I’m using the boiler for hot water only I realise it’s not turning off when the water should be well up to temperature. If I then turn the thermostat on the cylinder down a little then the boiler turns off. Can I safely turn the cylinder thermostat all the way down?
Another cost effective way is to set your immersion heater thermostat just a slightly lower temperature than what the boiler heats your water, this way the immersion heater won’t cut in at the same time while your boiler is running and only if boiler shuts down.