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Most efficient method for water heating?


johnnyboy
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Hi all,

Just a quick question on the subject of hot water, we currently use about €70 per month to heat just water by oil fired boiler system. Would it be any cheaper to heat by electric immersion heater.

Just for background info, normally just the two of us here and water used for washing, showering and washing pots and pans etc.

Currently have the plombier here trying to fix our solar water panels, which he has always insisted are working as advertised! Not as of this moment though, as there seems to be a blockage up at the panels.

Would be good to get any comparisons of people in similar circumstances for usage/cost.

Many thanks in advance,

Johnnyboy.

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Your figure of €75 per month equates to €900 per year.

That is almost exactly what we pay for all electicity, for two of us, including hot water, electric oven, microwave, washing machine, tumble drier (a high consumer), as well as all other appliances.

If you are using €75 p.m. worth of oil just for hot water it doesn't appear that the solar water panels are contributing anything.

An electric immersion water heater is the most efficient in terms of using the power supplied for it, although in terms of cost efficiency many systems might be more efficient, from boiling a kettle on a fire to solar panels, but might not necessarily be so convenient.

 

 

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Efficiency means getting as much of the energy out as possible as hot water compared to the energy put in as fuel, in those terms electrical heating being close to 100% efficient is the winner over any other fuel where a lot of the heat dissapears up the flue.

However other fuels can cost a lot less per unit of energy so that in the UK for instance its cheaper to produce domestic hot water using gas as a fuel than an electric immersion heater.

I am all electric here in France, heating, cooking, hot water etc, I have an HP/HC abonnement and the hot water and most of my heating is off peak, averaged throughout the year my costs have been €60 per month, maybe this last year a little higher.

Editted, just seen that the last posting speaks of "cost efficiency" probably explains it more concisely than my rambling.

€75 per month for hot water alone is a hige amount!

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By coincidence I was chatting to a plumber about this yesterday at one of the properties where I do maintenance.

Its a truly enormous dwelling with a fuel bunker in the basement feeding a boiler literally the size of a small van. Various electric circulation pumps feed dozens and dozens of radiators and various different zones of under floor heating. For hot water, the heating circulation pumps stop and another pump circulates the hot fluid through a heat exchanger in the water tank which is a six foot high cylinder.

The enormous distances between the boiler room and the furthest bathrooms would mean you would have to run the tap for ages before getting hot water through, so the hot water cylinder is plumbed into a continuous loop around the building and back into the cylinder, pushed by yet another electric pump, with short spurs off the loop to each hot tap.

He said that when he fitted the system at the previous owners request 20-odd years ago, fuel was very cheap and this was acceptable. However nowadays with fuel getting on for a Euro per litre and only ever going to increase, its madness.

He said that a decent quality electric cumulus is about the best you can get today with regards to cost effectiveness and convenience and if its at all possible to supplement this with other systems like solar, then even better.

The building is due to be extended further, adding 3 more large under floor heating zones in an adjacent building, which is planned to be run from the same boiler. The building is half finished and big feed pipes have been laid from the boiler room to the site. Whilst the current boiler has the capacity to run this extra load, he reckons is will drain the fuel tank in a matter of a couple of weeks. If it were his money, he said he would go for a second boiler in the new building that burns wood pellets or sawdust, which he reckons is going to become the Next Big Thing in France as oil and electricity prices rise.
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I am far from up to date as far as relative costs of gas and electricity in the UK are concerned, but I am not sure if your assertion about gas being cheaper is completely valid.

Maybe the actual cost of the energy is lower, but the cost of the installation, together with the purchase and construction of the flue, has to be amortised, and a large amount of heat simply goes up the flue.

From what I have heard from friends in the UK, if condensing boilers are used, which I believe are now compulsory, the condensed combustion products cause corrosion of the flues, which have to be periodically replaced, adding considerably to maintenance costs.

 

 

 

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You are right, I did not account for that at all!

I have just fitted a Combi condensing boiler to my UK property, it should cost less to run than the 45 year old previous boiler but its only the tenants that benefit, not the person who paid the money for it!

I recently found that the very  tendance multi-flue pebble effect gas fire that seems to appeal to everyone but me is only 50% efficient, 3kw output from 6.2kw input, more than half the heat goes straight up the chimney.

Interesting re the flues, mine is very short and just goes through the wall so should be cheap and easy to replace.

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You can't really seem to win in any situation involving flues.

I installed my first pellet stove with a gasketed joint, stainless steel, double wall flue, as specified by the (Canadian) manufacturer.

I had to install it through the roof as through the wall was into the street and a flue outlet wasn't allowed.

At that time (2008) the flue supplier, a qualified French expert, refused to supply gaskets for the joints, even though I had specified and paid for them in advance with my order, saying they were illegal in France and it was illegal for him to supply them, despite my showing him the manufacturer's specifications for the flue, in French.

So was forced to accept delivery, but had to source and get the (silicone rubber) gaskets from Italy, where they were and are quite standard, so the total delay in getting the stove fitted was nearly 2 months...

I see that the French manufacturer (Poujolat) of the flue I bought now produces a double wall st-steel flue specifically for pellet stoves, complete with, guess what? - yes, gaskets.

 

The instructions for installing the stove suggested taking the inlet air from the anulus of the chimney, thus pre-heating it and recovering some of the heat usually wasted, so I connected the 2" air inlet pipe to a suitable tee purchased with the rest of the chimney. This also has the effect of considerably cooling the outside surface of the flue within the house, which I thought was a good safety feature as well.

However, the resultant cooling of the exhaust gas by very cold air in the depths of winter causes increased condensation of tar and other products near the top of the flue, which are quite difficult to move during the annual cleaning.

If the flue has to be damaged during cleaning I prefer to do this myself, so I do it from the top, where I can see what is going on, but this a bit of a PITA.

A short flue through the wall would be far better, even if slightly less efficient.

 

 

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So does the type, design and length of a flue alter the efficiency of a gas fuelled condensing boiler then?

I confess to not really knowing how they work, very unusual for me to buy and fit something without fully understanding it but it was a winter breakdown and I had to drop everything and return to the UK to get the heating and how water up an running again after my tenant came close to burning the house down by tampering with the gas fire destroying it and nearly the house in the process.

Tampering being the manufacturers words, anxious to avoid any responsibility, failure to use in accordance with very poor operating instructions is nearer the mark.

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crikey!!! 75euros per month for hot water....we pay 50euros for all our EDF per month....(we burn wood for heating, otherwise everything else is EDF. I'd get yourself a good mid-range price water tank from any good Brico shop, get your EDF onto HC and HC and have the Cumulus wired up during the cheap hours....you'll have all the hot water you good want, if you get the right sized tank!!!!! As for the solar panels, are they really doing anything?????
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[quote user="Chancer"]

So does the type, design and length of a flue alter the efficiency of a gas fuelled condensing boiler then?

[/quote]

I don't think it makes a great deal of difference to the efficiency of a gas boiler, although I'm sure there are limits specified for installation..

In the case of a pellet stove, I'd rather have a shortish through-the-wall flue, for simplicity and lower cost of installation, and for ease of cleaning.

The length is not too important, so long as it is less than the maximum specified. A longer flue increases the amount of heat recovered with a balanced flue setup, but, as I indicated, tends to increase the amount of tar deposited.

 

 

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My balloon cost's me €10/mth for what is effectively unlimited hot water, as in we've never once run out even when we had 8 in the house this Summer.

I installed it as an alternative to using my oil boiler and a consequence 1500lt of oil will last me up to 3 years whereas previously I'd have been lucky to get 1.5 out of it.

I use flat rate electricity and the balloon is on a timer set to come on between 3 and 6am, it only consumes what it needs during that time of course.

If I'd done it when we first bought the house I'd have saved enough now to buy a replacement for the 18 year old boiler !

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[quote user="nomoss"]

From what I have heard from friends in the UK, if condensing boilers are used, which I believe are now compulsory, the condensed combustion products cause corrosion of the flues, which have to be periodically replaced, adding considerably to maintenance costs.

[/quote]

Unless you opt for a super efficient Keston boiler which uses standard PVC plumbing pipe for the flue as the gasses are that cool when they leave the boiler because more of the heat is sent where you actually want it.

http://www.keston.co.uk/our-products/system-range/system-30kw/

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We have a Chaffoteaux Fluendo instant hot water heater running off of propane gas. Lovely hot water in kitchen and 2 bathrooms whenever. We run it on the standard size propane bottles and use, at most, 6 a year which is under 180 euros a year. Very economical.

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Where do you get propane bottles for €30, a typical price around here for the standard 13kg bottle is nearer €40 (e.g. Mr Bricolage €37.70)

€37,70 x 6 = €226 so based on that my electric solution is getting on for 50% cheaper with no gas bottles to lug about either (or pay deposits on in the first place) [;-)]

I don't know which model of Fluendo you have but the cheapest one seems to cost about double that of a typical 200lt chauffe eau électrique along with potentially significantly higher installation cost's too unless you DIY. There is also the legally required annual flue cleaning to factor in.

I still have hot water during power cuts too, a very frequent phenomena around these parts !

Hard to see any advantage to going that route then.

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We have three electric hot water tanks installed, would not have anything else. Cheap to buy, easy to install, virtually no maintenance (you are supposed to check the operating of the security valve). To avoid a long cold leg, we installed a smaller one in an en suite a long way from the upper main tank. All heat up on over night cheaper rate.

The old three phase one we have just replaced was well over 30 years only. One thing to consider is the hardness or softness of your water which will help dictate the sort of heater element you need.

A replacement 150 litre tank was only slightly more than our neighbour pays for the yearly contract clean of their gas combi boiler.
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Many thanks for all the interesting replies, much food for thought!

Had a quote recently to fit an immersion heater in the existing ballon which came out at €1,400 approx, was thinking of going down that route until I got the devis.

As for the solar panels, I've just been informed by one of the guys that they think the collector panels themselves are blocked. Deep joy. No wonder the system has not performed. We had another entreprise come and do some troubleshooting and they confirmed that the expansion tank had a leak on the air side of the diaphragm and that as it was around the visual indicator, it may well have been there for a long time. That would explain why we had to get Mr D**khead back at least once a year to top up the fluid, always leaving saying that "toute marche bien". I begged to differ, but was made to feel as if it was me that was not quite right!

He only came back yesterday after receiving the letter from us and "Que Choisir" to look at the problem. He last came 8 weeks ago, topped up the system and left saying he'd be back in a couple of days!

I await further news with trepidataion.

Johnnyboy

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Well Johnnyboy

When your solar system does eventually get up to speed and there is really no reason why it shouldn't (perhaps with the exception of .... installers who are not great at their job) then you will have the advantage over most if not all of the previous posters. The future for them is certain - certain to feature rising costs and as they have chosen these bought fuel systems with no thought for the future, then, up and up and up it will go (the cost of their fuel).

Whereas yours (and mine ) will never change not so long as we live - our cost was (virtually)NOTHING when we installed it; it is NOTHING today and it will be NOTHING in 50 years to gain all the energy we can from the sun to heat our water. We have chosen to take advantage of the radiation which is available to everyone, only not everyone want's it (something I really don't understand). I'm more than happy that my 120 tube system has paid for itself in cost savings, more than happy that it does for most of the years HW and more than happy that it contributes to the heating of house besides (especially during these glorious sunny winter days). I'm a happy man, hope that you will be too.

Fuel prices can do what they like... I'm OK Jack;

O

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[quote user="Oracle"]

We have chosen to take advantage of the radiation which is available to everyone, only not everyone want's it (something I really don't understand).[/quote]

Maybe you would understand better if your house roof faced north, or you didn't expect to live another 50 years[:D]

 

 

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Have to say I am always sceptical about claims that things effectively cost nothing.

I have just done a quick calculations which is as follows.

One hot water tank in my house runs only at night. The current price, (looking at my most recent bill) is around 6.5 cents per Kwh (including taxes). My tanks have 2kw heaters so thats 13 cents per hour. Although they run for 8 hours per night they probably heat for around six (or even less but I am being generous) which makes it 78 cents per charge. The system runs for 365 days per year which makes the total cost 285 Euros per year. This also assumes I use every single drop of hot water when in reality I probably use half a tank per day on average so it should be cheaper.

The average price (from looking around the Internet) is about £2,500 for everything you need to fit a solar water heating system which is about 3,000 Euros. Now it needs to be installed and I have no idea how much this would cost in France but lets say another 2,000 which includes any decoration and making good which takes us to around €5,000. Just in case in case I have overdone it a bit which I don't think I have I will ignore the running costs of the circulation pump.

Right now lets say it will produce hot water for 10 months of the year. By that I mean hot enough to bath, shower etc with no other heating source. This means I have to take for comparison purposes two months of my current system which makes the total 237 Euros for ten months per year.

So 5000/237 = 21. That means I can stay where I am for the next 21 years and it will make no difference if I use solar heating or electrical heating for my hot water.

If anyone wants to correct my calculation I won't be offended as it has been done quite quickly since I am renovating a bedroom at the moment and just took a few minutes out to try and work it out.

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Quillian

Yes an attempt but too pessimistic.

If you rely purely on cost/payback calcualtions to make this particular decision, then you could probably convince yourself of anything. Just get the right numbers and it looks great or conversely like a disaster. Most of the people who buy solar are a fair bit more sophisticated than that, including me, I use reason too.

So if you are stuck with your pêncil and your calculator then consider the following;

  • whole of life cost, including increases in the price of energy
  • you didn't say how much water you need but let us say its 200lt -€5kis on the high side, €1000 installed is also possible
  • more and more home owners think that its a responsible choice, home value increased.
  • Its a simple system, very little or no maintenance or replacement cost.

there are lots of other reasons, but you either like it or you don't.

O

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I haven't read the thread carefully - just to add my comment that we have a condensing boiler run on gas, installed in 2006, and the best thing about it is the supply of hot water.

We use the boiler for hot water, heating the house, and cooking. 2000€ pa.

Plus installation, but we got a big refund from the Impots.

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Well yes I am. I wouldn't install something just for the sake of saying I am 'green'.

Even if I were to say that with the increase in French electricity prices the time dropped to 11 years it still wouldn't be worth doing because if you want to cut bills in general the money can be more effectively spent on other things which give a much better return.

We have 200L tanks (four of them but thats because we are running a business) and we use, as I said in my previous post, around half a tank per day. So if anything I have made my electric water heating price about double than it really is but I wanted to look at 'worse case'.

When I build my 'retirement' house from scratch it would be something I would seriously consider as my aim would be to live almost 'off grid'.

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I like your calculations......I have seen many a Brit and Frenchy go down the solar panel road. I hope they do it for the eco-green thing, because as you say, 20 yrs to get your costs back!!! Even if it was ten yrs, it still aint worth it given that the average stay in a house in France is 7yrs!!! EDF is going to have to increase radically in order for these alternatives to become attractive....
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