Smart meters + direct unvented water cylinders + THTC. Any advice welcome!

Again, thanks! That's great to know, the guy i spoke to earlier today when quizzing i don't really think got my point, didn't really seem to think any form of boost may be needed with the new system, but likely explained it as clear as mud to him. Really appreciate the advice there, I'll check in with them again this week 

No worries, glad to help.

It just so happens that I have a few magic tricks of my own. One of which is that I’ve got direct contact with a Smart Meter Engineer. Perks of being on this Forum - we can reach him anytime. :D

Brill, keep up the good work! Lots of confusion and concern out there....thanks again.

This system is designed for households where when everyone has had a bath, there’s no hot water left to wash up with. It will work in exactly the same way with a smart meter. When it’s on Timed, the immersion heater will get its power from the switched circuit that is only live during offpeak hours*, along with the storage heaters. If you run out of hot water in a peak period, you can use the boost to heat a bit more, at peak rates, obviously. 

*  If the main immersion heater were on a constant circuit, i.e. with power 24 hours a day, it would have its own time switch to limit its operation to offpeak times. There may be a second  heating element near the top of the tank that gets its power from the constant feed to provide the boost function.   

​@Firedog thanks also. Next step is to look at the tariffs. Domestic 8 is 8 hours overnight, Economy 9 and 10 split over three sections off peak through the day. I don't know how effective the latter two would benefit our set up though - ie High Heat Retention Quantum radiators still using off peak through night, to be timed through the day. And also that the price difference between peak and off peak doesn't seem to be much difference for the 9 and 10. Standing charge same for all 3 by the looks.

IIRC Quantum works pretty well on E7/Domestic Economy, E9 and E10. It should ultimately be down to whatever else you’ve got and how that needs to be charged up.

​@Blastoise186 thanks, yeah just the water cylinder the main other thing. No panels or heat pumps to factor in.

Got it. E10 might work but definitely discuss with OVO as they have more data access than me.

Heat Pumps DO NOT work well on these Multi-Rate Tariffs though - they’re best on Flat-Rate.

Brill, certainly will do when speak again. Much appreciated thanks.

These are very different plans with different prices. Which is most suitable depends a lot on your lifestyle and on how far you’re prepared to go to pay more for more comfort.

You say you’re in the West of Scotland; the mainland coast stretches from the Solway Firth to Cape Wrath and is served by two electricity distribution companies (DNOs). Scottish Power does the southern bit as far as the Firth of Clyde (region 18), while North of that it’s SSEN (region 17). Their offpeak timings and the prices are not the same.

Another factor is your current THTC set-up. Some plans included a 24-hour  lower Heating rate, so it cost no more to run a 2kW fan heater at 9 in the evening than at 6 in the morning. This all changes with the new single smart meter arrangement; all usage during offpeak hours is charged at offpeak rates, whatever it’s used for, while all usage during peak periods is charged at the higher rate regardless of what for. 

If your storage heaters are working satisfactorily - i.e. they accumulate enough charge overnight to keep them pumping out warm air all day, and they’re big enough to keep the space warm, then Economy 7 could be the best option, with its attractive offpeak rate. It is after all the storage heaters and the immersion heater that will be taking the lion’s share of your total consumption.

If on the other hand you find that there’s a need for extra heat in the evening, one of the other plans may be better, because they both allow for heaters to be run at offpeak rates for a few daytime hours. The unit price is quite a bit higher, though, so you’ll have to dig out the slide rule and do some serious sums to work out how best to keep comfortable at an affordable price. 

Sadly, there is no ‘one size fits all’ answer to the question of which tariff would be best.