Bearing in mind our Bathroom Hot Water comes from oil… even Queen Elizabeth (whichever) would have to prove a real need for a hot shower… cold water is OK, especially using the bucket system 
Since self installing an array of 8 PV panels (cost 2.8k), we have had free hot water and plenty spare electricity. All spare electricty is used to heat hot water (250l ballon) and then the remainder is exported to the grid. We have exported more electricity to the grid than we have imported. Unfortunately, we are not paid for our exports.
We have an air source heat pump so in summer we use the spare electricity for air conditioning.
Here is the data, unfortunately the database was corrupted so I lost the Nov - March data. The orange is generated electricity, blue is imported electricity and purple is exported.
The tubes are so much more efficient because of the vacuum (think thermos) so heat loss is minimised, often you need to loose additional heat or cover the tubes.
Thats why they can generate hot water in Antartica, they use light very effectively.
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Then why do it? Maybe get a home battery supply and inverter and use it all yourselves.
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the tubes through the panels were great and we got our money back in a couple of years… that was a win-win.
Sadly never could find it here in France, although we looked and looked.
Why are you not paid?
The costs to enable you to earn money through exporting outweigh the benefits. Similarly a battery to save the last 3kWh I import every night/early morning does not justify the costs. You can have a “virtual battery” offered by Urban Solar (https://www.urbansolarenergy.fr) , but again, the costs are not justified. I am happy to export in the summer but in winter there isn’t much left to export after using the air source heat pump for heating.
When we install ours that is certainly what we will do, especially if EDF is struggling and there are power cuts. Why give power to them and then find there are times when we are cut off?
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Sorry my mistake, thought you were exporting more. Speaking of batteries, whilst not perfect being lead acid (space, weight and capacity) fortunately two large UPS’s were recently scrapped at work so I helped by reducing their cost for removal and for my forthcoming solar project. 
I intend to use solar thermal for water heating as its much more efficient than PV in that area, would love 60+ tubes to take the load off the underfloor etc.
SuePJ. Unfortunately if you are connected to the grid and you use PV panels, if there is a power cut, your panels will stop generating electricity immediately. This is intentional to protect workers who may be working on the wires.
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Not water, it’s a special liquid that can tolerate extremely high and low temperatures. Very efficient so far.
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Is it cost effective? It certainly is more space efficient. Solar PV may be less efficient but much cheaper to install and less maintenance? Plus you produce electricity which can be used for other things besides heating.
Obviously a more modern idea… our set-up was back in late 60’s early 70’s…
Cost efficient? I weighed it up with PV and using the emersion but it worked out that with a huge amount of water it’s cheaper for us to use panels. PV next year with storage so we can be independent of price hikes. Most of our bill is behind the scenes stuff and it sticks in my craw not being in charge of my own money. Power cut tomorrow for 5 hours while they work on something in the whole area and again on Friday while they put it back. Time like this it’s handy being off grid.
I can now very much vouch for the goodness of cold showers Before the pump went out of action I took some cold showers out of choice, following Wim Hof, but now I don’t have an alternative, I am now quite used to cold showers - every cloud 
And I’ve mastered having a complete ‘shower’ with 6 x 1.5 litre bottles of water - not sure I’d like to be doing this in the depth of Winter though 
We have a very similar system. It didn’t cost us anything extra to export the electricity except the yearly TURP charge, which I think is around €36. We earn about €250 per year for our exported electricity and like you pay almost nothing for our how water as excess is diverted to the got water tank before being exported.
I assume your installation was done professionally. There are numerous hoops you have to jump thru if you install the panels yourself and wish to export electricity which increases the costs. I opted to keep the installation costs down so my payback for my system is around 5 years.
I am thinking that a Citroen Ami would be an ideal way to use all excess electricity generated. Pity the car battery cannot be used to power the house overnight.
It would, but wait a while and bi-directional battery use will come, some have it already, possibly the little renault but that failed to get any stars in the EuroNCAP so I would avoid it.
Yes, ours was done professionally three years ago. We had 2.1Kw in 7 panels added to the existing 2Kw. We also had a new box to control all the microinvertors and various electronic gizmos to monitor the flows of electricity and divert excess to the water heater. We also had to have the existing installation brought up to spec as it wasn’t. Curiously, after the refund from Prime Energie (paid over 5 years, so were still getting it) we won’t in the end pay that much more than the price you quoted.