Back in UK around 1975, we had 2 panels installed on the roof, which provided all hot water requirements throughout the summer - no oil needed - and in winter they pre-warmed the cold water feed to the Balloon, reducing the oil needed. There was a valve to switch between the 2 systems.
In that installation - we got our money back in 5 years - quicker than quoted. hurrah.
I was hoping Chris would give us some more details of his situation and how he got interested in electric boilers as a solution. It might well be that, in his particular circumstances, they are a good idea.
These boilers are “efficient” which might have caught his eye but that’s only in terms of transferring heat to the water within the boiler - it doesn’t fix losses elsewhere and, as Robert says, using electricity to heat water is about the most expensive way of doing it. Modern gas boilers also reach efficiencies in the high 90’s percentage-wise, even modern oil boilers can be pretty high.
To compliment the link Robert posted, Selectra also has some comparisons:
I haven’t verified the figures - that for electricity seems slightly high, but if we take them at face value, in Peter’s case assuming a COP of 3 in the winter months he might expect his bills to fall by about 33%, if he only gets a COP of 2 then he might not save that much (but that is probably a bit pessamistic, especially averaged over the whole year). In Chris’s case (also currently with an oil-fired boiler) one might expect his running costs to double with an all-electric solution unless he does something to mitigate this.
Of course, as noted above he also needs to switch from a single phase to three-phase supply to use the Heatrae sysem for his heating & DHW.
Sorry John, not quite following you there - are you just talking about the fact that monophase supplies are 12-15kVA at most, needing three-phase for anything more (in the UK urban domestic supplies are usually 100A, but it is sometimes less, especially in rural locations).
As I said above if you really want to do it with an electric boiler (and I agree it does not seem the best solution) the Heatrae Amptec units would parallel to give a workable solution.
and we with a similar sized property spent 1,000€ last year for heat light and power even with a heat source pump running warm air in winter and cold in summer.
Not bad - we’ve 150m2 (plus a bit) and, were we there all year, I think we’d be closer to Dan’s 1600€
Ours is a new build wooden house - external walls 200 thick with rockwool insulation, 200 density insulation in the concrete floor (wood composite flooring) and 200 in the roof. All internal walls are wood frame with 100 rockwool insulation sandwiched between the rooms.
We do have a single Godin wood burner in the lounge which heats the whole house in winter but have found since installing the heat source pump that we have lit it much later than we used to. When the burner is going full tilt, we have to open the house up right through to what we call the garden room which is on the north facing part of the house before we start stripping off 
The mind boggles Graham…
hope you put the cat out first ?
We have inefficient electric radiators. We mostly use our woodburner and only put our hot water tank on for 2 hours on alternate days.
I would love a proper heating system but assume for our 3 bedroom house with a salon and kitchen/family room it would be a lot of mess and expensive to install. I have no idea of costs. Is their any merit in just staying as I am but with an extra wood/pellet burner?
Also what electric radiators should I be looking at?
How good/efficient is your house insulation ?
Do you have tiled floors etc ?
we considered that until I read somewhere that there is a risk of listeria from water heaters which do not maintain or return water to the optimum temperature in a timely fashion.
Add to that the equation (which I’m sure @anon88169868 will comment on at some time) about the cost advantages between leaving the water heater to switch on automatically during the heures creuse (cheap rate) daily to top-up the contents of the cylinder to temperature and heures plein/creuse in a situation of need ('cos the water has gone colder than desired) which might require more electricity usage to restore a colder cylinder to optimum - if you see my point.
The loft is well insulated, not sure about walls. The floors are tile /laminate.
We don’t have any cheap rate electric. Also our heater for the kitchen sink is a small one which we never turn off. Our large water tank is just for personal hygiene.
Our laminate floors are constructed as a sandwich - light oak finish upwards, cheaper wood downwards and an insulate in between. We also laid an insulating material down on the concrete floor before installing the parquet which stops the ‘tap tap tap’ on the concrete as you walk over it (I’m no Fred Astaire).
More like Fred Dibnah !
Electric radiators are efficient at turning electricity into heat. What they may not do is give you a great comfort feel as they don’t radiate very far 1 meter at best probably less. a small fan assisted radiator is the same efficiency but the comfort factor is vastly improved as warm air is forced around the room giving a quicker warm feeling.
Hi Paul, it’s more to do with the 80-100 amp on tap we have in the UK. In France you need a big abandoment for something you may only use in winter (electric heating for example)
If you have AMPTEC boilers on a large available supply no issues but France’s supplies are just not set up for that although I will be looking into the electric car charging tariffs to see if that give more flexibility.
That’s interesting as I want new laminate. Could I put new laminate on top with insulation
in between?
probably… no reason I can think why not 
Might have to trim the bottom of the doors?
Probably.
Probably a bit complex to generalise completely - depends on tank size, insulation and usage pattern but some points to consider, in no particular order are:
You pay to heat the water you use, obviously
You pay to replace heat energy which is lost from the storage tank - this will depend on the water temperature, or rather the difference between the water temp and the environment and the amount of insulation - the bigger the difference the faster the heat loss - so keeping water constantly at 80°C will use more energy than keeping it at 60° Allowing the water to cool for a while, then reheating will use less energy than maintaining a constant temperature because the average temperature is lower and hence losses to the environment are lower - this is especially true if the tank cools down fully between heating cycles (but then you’ve got no hot water).
The better insulated the tank the less the heat lost.
Too large a tank will cost you money as you heat water you never use - BUT - a larger tank will cool more slowly as it has a smaller surface area to volume ratio.
So, ideally you want to keep the water cool and heat it just before use, and preferably just heat what you want to use - this line of thinking leads to point of use instant heating systems.
Best pattern of use with a tank is probably heat overnight on heures creuse, use all the stored hot water in the morning for bathing, do the pots once a day either in the morning while the tank is hot or in a dishwasher (modern ones just heat the water they need), also on heures creuse and leave the water in the tank cool (and not losing heat) during the day.
If you must have hot water in the evening heat it just before you use it