Electric 'flow boilers'....
These used to be called 'electric boilers', but now the manufacturers seem to
want us to call them 'flow boilers' for some reason. (My English teacher at
school would have called this redundancy.)
Anyway, 'flow boilers' are little more than an immersion heater in a pipe.
They have some sophisticated electronics in them apparently, but I'm not sure
why they need 'sophisticated electronics'. I'm not a fan of electric flow
boilers (can you tell?)
They were developed and marketed originally by a company called Amptec, from
Basingstoke, to allow a wet central heating with normal radiators to be powered
by electricity. The trouble is, this is normal, day rate (i.e. EXPENSIVE)
electricity. Amptec made some false claims about low running costs and were
driven into insolvency (I believe) by a series of customers successfully suing
them, and the company has now been taken over by HeatRae Sadia.
HeatRae Sadia are planning a major marketing push for Amptec boilers again
now, but because of the huge running costs I expect them to remain a specialist
niche product. I've never seen one fitted in a real dwelling.
See HeatRae Sadia's Amptec page here
Trianco (the oil boiler manufacturer, not the model train people) also make
two electric boilers, both called "Aztec". See them Here.