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Zdave94
The multi rate tariffs are only supported by SSE and OVO if memory serves, so most other suppliers would not have a scooby.
I'm assuming you are too young to remember the 'Heat Electric' adverts from the 70s, but when we had plenty of cheap electricity (more nuclear than we have now and coal being shovelled into coal-fired stations at a rate of knots) there were special deals on all-electric heating.
Southern Electric and Scottish Power (now part of SSE) offered specialist tariffs which had your regular Economy 7/10 which everyone can manage, but special rates per unit for running storage heaters at night, and heating up your hot water. This was when electricity companies and gas companies were completely separate industries, and the electricity companies were trying to get a bit more trade by offering to heat your home/water rather than you paying the gas board for the priviledge.
These deals have long since vanished as these systems have not been installed since the early 90's - I myself had such a system down in Hampshire in a new build in 1992.
So, only the few companies that offered these packages are capable of figuring out the extra rates and the complex tariffs involved.
I know the people who live in my old house (they bought it as a buy-to let when it was first built and I rented it off them for three years) and they had no end of palaver trying to get it updated.
It is doable, but takes a bit of work getting the wiring modified, and then the meter replaced. I did the electrics side of things, being an electrician, but the meter update was rather more complicated.
The process went something like.
1. I removed all the storage heaters and the 'heat rate' immersion heater.
2. I disconnected all the 'heating' wiring right back to the meter.
3. The electricity supplier had to be convinced that we wanted to do away with the SuperHeat deal and could they please come and replace the meter with a conventional dual rate meter. I explained that the 'all electric' heating system had been removed and demanded that the meter be replaced with a dual rate meter, which they eventually conceded to.
4. I added the appropriate MCB's to the existing consumer unit and rewired the immersion heater and a couple of storage heaters (it was a one bedroom 'studio house') to allow them to work properly but under the 'conventional half' of the meter, so working on the same day/night rates as the rest of the house.
5. The supplier then 'removed' the second MPAN leaving just a standard E7 setup with two rates and one standing charge.
Not impossible to do, but a bit of a bugger trying to get the energy supplier to play ball. Once they came round to our way of thinking, everything was much simpler all round, especially for the billing side of things.
Alternatively, your only real option is to go with a supplier that still supports these complex tariffs - SSE or OVO.