Is it cheaper to heat water with immersion or gas?

wittynamegoeshere

Snookie12cat said:

RobM99 said:

As an aside, is your cylinder insulated?

Yeah, brand new Megalow Eco so it should be the best it will ever be right now. 

I'm intrigued, why do people have hot water cylinders installed these days?  Was a combi-boiler considered as an option?

I fundamentally don't get the purpose of heating a vast amount of water every day just in case you might need it then leaving it to go cold if you don't.

Snookie12cat

wittynamegoeshere said:

Snookie12cat said:

RobM99 said:

As an aside, is your cylinder insulated?

Yeah, brand new Megalow Eco so it should be the best it will ever be right now. 

I'm intrigued, why do people have hot water cylinders installed these days?  Was a combi-boiler considered as an option?

I fundamentally don't get the purpose of heating a vast amount of water every day just in case you might need it then leaving it to go cold if you don't.

I moved in recently and it was already here, but it sprung a leak and surprisingly was under warranty so we were given the £1200 tank for free.
We thought about a combi but I like the idea of future proofing the house. If you get solar panels you can heat your water for free. You get a heat pump you need a tank. Because it was free we figured best to keep it. 

Snookie12cat

Alnat1 said:

It might be better to have one longer period for heating the water by gas, rather than 2 short ones. Your brand new tank should lose very little heat, so the water will stay hot for 24 hours if not used.

We heat ours for 40 minutes each morning, does a couple of showers, hubby's shave and a bit over. It used around 3.5kWh over summer, now around 5kWh I think, as the incoming water is colder. Harder to tell as the heating's on too

Our tank is 170L. If I heated it in the morning for say 40 mins instead would that give enough water for a 20 min shower in morning and 20 mins shower in evening? I guess I worry that if I dont heat it twice a day then there wont be enough water. 

Is your water at night hot enough if you have not heated it since the morning and do you think its cheaper doing it this way?

k_man

Snookie12cat said:

Alnat1 said:

It might be better to have one longer period for heating the water by gas, rather than 2 short ones. Your brand new tank should lose very little heat, so the water will stay hot for 24 hours if not used.

We heat ours for 40 minutes each morning, does a couple of showers, hubby's shave and a bit over. It used around 3.5kWh over summer, now around 5kWh I think, as the incoming water is colder. Harder to tell as the heating's on too

Our tank is 170L. If I heated it in the morning for say 40 mins instead would that give enough water for a 20 min shower in morning and 20 mins shower in evening? I guess I worry that if I dont heat it twice a day then there wont be enough water. 

Is your water at night hot enough if you have not heated it since the morning and do you think its cheaper doing it this way?

All systems are slightly different, so you would only know by testing.
But, a modern cylinder should not lose significant heat between morning and night.
Also, with gas water heating, there is a overhead/wastage getting the system upto temperature each time, and you get this twice, if heating water twice a day.
This can be as much as 2 - 3 kWh. I noticed this when I used to heat water 3 times a day, and realised the lunchtime heat was using nearly as much as the other 2, even though virtually no hot water had been used.

If GCH is already on, then this effect is minimised, as the system is already warmed up.

I have mine now set to come on for 90 minutes once a day but it is only ever heating water for about 45.
Being on for longer means there is always a full tank, just in case more water than normal is needed.

ETA: just noticed this, a 20 minute shower is a long shower, and will use a lot of water. So one full hot water tank/heating cycle may not be enough for 2x.

Snookie12cat

k_man said:

Snookie12cat said:

Alnat1 said:

It might be better to have one longer period for heating the water by gas, rather than 2 short ones. Your brand new tank should lose very little heat, so the water will stay hot for 24 hours if not used.

We heat ours for 40 minutes each morning, does a couple of showers, hubby's shave and a bit over. It used around 3.5kWh over summer, now around 5kWh I think, as the incoming water is colder. Harder to tell as the heating's on too

Our tank is 170L. If I heated it in the morning for say 40 mins instead would that give enough water for a 20 min shower in morning and 20 mins shower in evening? I guess I worry that if I dont heat it twice a day then there wont be enough water. 

Is your water at night hot enough if you have not heated it since the morning and do you think its cheaper doing it this way?

All systems are slightly different, so you would only know by testing.
But, a modern cylinder should not lose significant heat between morning and night.
Also, with gas water heating, there is a overhead/wastage getting the system upto temperature each time, and you get this twice, if heating water twice a day.
This can be as much as 2 - 3 kWh. I noticed this when I used to heat water 3 times a day, and realised the lunchtime heat was using nearly as much as the other 2, even though virtually no hot water had been used.

If GCH is already on, then this effect is minimised, as the system is already warmed up.

I have mine now set to come on for 90 minutes once a day but it is only ever heating water for about 45.
Being on for longer means there is always a full tank, just in case more water than normal is needed.

ETA: just noticed this, a 20 minute shower is a long shower, and will use a lot of water. So one full hot water tank/heating cycle may not be enough for 2x.

Thank you - I googled how much water does a 20min shower tank and it suggested the whole tank! I have however fitted one of those restricted heads and because our water pressure is insanely high we don't need the tap on very high to get a good shower, so if I was using the entire tank I would be disappointed. 
Ill try heating it once a day and see how we get on. We do not always need it every night either so are heating it for times is not even used.

Ha ha, yes - my son LOVES a shower, twice a day... he is autistic so we tend to let him have that because he loves it so much. Thank god our water is capped! 

Apodemus

Snookie12cat said:

Alnat1 said:

It might be better to have one longer period for heating the water by gas, rather than 2 short ones. Your brand new tank should lose very little heat, so the water will stay hot for 24 hours if not used.

We heat ours for 40 minutes each morning, does a couple of showers, hubby's shave and a bit over. It used around 3.5kWh over summer, now around 5kWh I think, as the incoming water is colder. Harder to tell as the heating's on too

Our tank is 170L. If I heated it in the morning for say 40 mins instead would that give enough water for a 20 min shower in morning and 20 mins shower in evening? I guess I worry that if I dont heat it twice a day then there wont be enough water. 

Is your water at night hot enough if you have not heated it since the morning and do you think its cheaper doing it this way?

By my calculation, if you started at 55C and want to shower for 20 mins at 40C, with a shower flow rate of 6L/minute and a cold water temp of 10C, you'd use about 80 L of hot water out of your 170L tank.  Even if it is set for 65C, you'd use about 65L.  When that hot water is replaced in the tank by cold water, it will bring your tank temperature down to either 41C or 48C.  With no further heating or heat-loss you would struggle to get an evening shower out of that, you certainly would be adding very little cold to the flow! 

And all that is with incoming water at 10C, the situation would get worse as water temps get colder through the winter.  Just how cold depends on where you are.  My mains supply can get as low as 4C...!

So in your circumstances, I'd stick with the second boost to water heating in the evening.

Alnat1

Our heating comes on at 6.30 and the tank is set to heat 8.00-8.40. I'm no expert but it seemed to me, if the boiler was heating the tank when the house was up to temp. it might use a bit less gas as it was already warmed up. 

mksysb

wittynamegoeshere said:

Snookie12cat said:

RobM99 said:

As an aside, is your cylinder insulated?

Yeah, brand new Megalow Eco so it should be the best it will ever be right now. 

I'm intrigued, why do people have hot water cylinders installed these days?  Was a combi-boiler considered as an option?

I fundamentally don't get the purpose of heating a vast amount of water every day just in case you might need it then leaving it to go cold if you don't.

Because when your combi breaks down, you'll have no hot water until it is fixed.  With a tank you have a backup immersion heater.

[Deleted User]

mksysb said:

wittynamegoeshere said:

Snookie12cat said:

RobM99 said:

As an aside, is your cylinder insulated?

Yeah, brand new Megalow Eco so it should be the best it will ever be right now. 

I'm intrigued, why do people have hot water cylinders installed these days?  Was a combi-boiler considered as an option?

I fundamentally don't get the purpose of heating a vast amount of water every day just in case you might need it then leaving it to go cold if you don't.

Because when your combi breaks down, you'll have no hot water until it is fixed.  With a tank you have a backup immersion heater.

And if you do solar thermal, or use a diverter on solar pv, or get a heat pump, you don’t need to re-plumb and install a tank.

wittynamegoeshere

mksysb said:

wittynamegoeshere said:

Snookie12cat said:

RobM99 said:

As an aside, is your cylinder insulated?

Yeah, brand new Megalow Eco so it should be the best it will ever be right now. 

I'm intrigued, why do people have hot water cylinders installed these days?  Was a combi-boiler considered as an option?

I fundamentally don't get the purpose of heating a vast amount of water every day just in case you might need it then leaving it to go cold if you don't.

Because when your combi breaks down, you'll have no hot water until it is fixed.  With a tank you have a backup immersion heater.

Yes, but I also have just one car, washing machine and hoover.  I don't have a backup for everything just in case, especially not if it's going to cost more.

I didn't want to get into the usual gang wars that seem to go on around here, where it seems that many are avidly pro or anti any subject that happens to come up, and will argue to exhaustion.  Just interested in why people still have cylinders having read that it was new, and a sensible answer was given that makes absolute sense.

Personally, having moved from a house with a combi to one with a sillynder(!), I find them very annoying and inefficient.  I was used to having limitless hot water with no planning and not paying to heat water I don't want to use, so it seems like a very backward step from my perspective.

We used to have occasional issues with the old combi - the diaphragm that detects hot water flow is prone to wear and needed replacing a couple of times, not a big deal and it's an (advanced!) DIY job.  Conversely diverter valves on cylinder systems seem to also fail quite regularly and it's at least as complex to fix, probably more so I don't think there's an obvious winner as far as reliability goes.