Hi kumkat:
I consumed 22Kw on the 2009-2010 heating season and for the moment 14Kw on 2010-2011 (thanks to the caulking of the conduits among others)
These units are weird and make no significant sense !!
14KW is a power watt = joule per second and therefore in a winter it must be in multiples of 10000KWh !!
Because the power of 14KW has worked for thousands of hours for example on the number of hours over 6 months is 24x6x30 = 4320h which gives 10KW of average power: 43200KWh
Probably you are less than half ???
But if you don't have a minimum of technical knowledge, you are ideal prey for scammers who talk nonsense!
In addition, low-end boilers such as the 12-year-old that you have are scams, with a real yield lower than what is written and designed to be changed every 10 years !!
More than 35 years ago I had a new boiler on my new house of the brand that you have, a real gas plant (why keep it simple when it can be complicated), uninsulated, which I changed before his death, in another insulated boiler, no more expensive, chosen for its technical simplicity and which 25 years later still gives satisfaction !!
Obviously it is not manufactured any more because too reliable by its simplicity !!
On another econology post, answering a question like yours on a well-defined boiler, I was surprised to discover that my boiler from more than 35 years ago, it continues to be done, almost unchanged , obviously, since it is an annuity for this type of boiler manufacturer with a lifespan designed to be changed often !!
All the faults of more than 35 years ago that annoyed me have been preserved !!
Boiler, not insulated, with instant hot water and expansion tank designed to be an annuity in repairs for plumber, and possible mode of regulation with external sensor, which is an absurdity !!
Also look at what I wrote about another brand on another post that I must find !!
But my simple boiler has become untraceable, since the few low-end manufacturers all have the same methods, designed for those who do not know the technique and have little money !!
Otherwise, to have better and simpler quality, you have to pay more, even if the boiler costs less to manufacture in reality, but since you don't have to change it often, you make the disappearance of the annuity in breakdowns pay dearly and in changes !!
However, often the breakdowns are secondary details that can be repaired yourself, driven by the expansion tank designed to lead to many troublesome breakdowns, which you can repair yourself !!
I am surprised at your sentence:
The heating body is starting to tire and I suspect it is the cause of my pressure losses on the network.
because in general the copper heating body has no reason to weaken with the gas which is not very corrosive, and in my opinion it is the expansion tank, which causes these problems, and 9 times out of 10, it is enough change it with a few small additional details and your boiler will work again for 3 to 5 years, lifetime of the membrane !!
It is all the interest to be interested in the technique, because if not the pro scammers take the opportunity to change the whole boiler, even for a fuse (numerous TV demos!) Or the expansion tank, him hyper- studied to die quickly !!
Me, I solved the problem, it became eternal, by mounting it as we did 80 years ago on simple boilers without electricity, in a word, as far as possible from the boiler !!
Result no more breakdowns !!
Look for my other responses to other post on gas boiler !!