Hey there @dmacbrew  !

I have some very good news for you and I’m also happy to clarify this one.

As you’ve got Economy 7 on a Five-Terminal setup, the storage heaters are wired up in a way that means they only ever operate during the cheap rate unless you activate Boost Mode outside of those times. However, ALL your usage during the Off-Peak hours will be charged at the cheaper night rate regardless of what you’re doing, not just the storage heaters.

On the flip side, all usage during the Peak hours will be charged at the more expensive day rate.

Hope this helps. :)

Thank you Blastoise186 that`s what I thought, especially as I was still getting billed for off-peak use in the summer when the heating is off. Why then I wonder did the engineer (who was very good & seemed knowledgeable think otherwise?). He even pointed out the cables going into tthe meter..

Hard to say I’m afraid. I don’t have psychic powers and can’t read minds. :)

However, as luck would have it, I happen to know an OVO Engineer. @Lukepeniket_OVO has been with SSE for quite a long time and also does OVO installs these days. His experience proves quite useful in some of the more tricky cases where we’re struggling, but I try to avoid calling on him too often, because he gets pretty busy!

You know @Blastoise186 you can call on me whenever  

As Blastoise has already pointed out because of your 5 terminal set up then the whole property will switch over to the low rate during your off peak times.

There is only a select few areas and setups which don't swap the whole property over.

Hope this helps?

Well what areas/setups?

I've raised a query tonight about that answer by Blastoise186

Where? 

And perhaps more important, why? It’s clear enough to cover most cases. 

Assuming that the meter installed a year ago is a SMETS2 model, then there are two mechanisms at work: one that determines which meter register records consumption, and one that powers up the circuit for the storage heaters. The meter will start recording on the offpeak register at the start of the cheap rate period and switch to the peak register again at the end of it. The meter doesn’t care which circuits the electricity is passing through, so there’s money to be saved by running other power-hungry appliances - dishwasher, tumble drier, EV charger, for example - during the night. 

Having a separately switched circuit for night storage heaters is convenient for many users who are happy to just leave them on all winter, knowing that they’ll only heat up when electricity is cheaper.

If you have doubts about your own arrangement, feel free to give us some details of it.

"Unless you activate boost mode outside those times" is the point. With the assistance of my recently installed smart meter I think I have deduced that Boost mode refers solely to the speed of heat release from the storage heater - whenever it's released. This would mean that if boost mode is applied during the nighttime then more energy will simultaneously be required to recharge the bricks. If the storage heater is indeed hard wired ONLY to the off peak meter (seems to be the case you're making) then it's reasonable to assume that there's no way the storage heater will switch behind the scenes to Peak rates

There are 2 things to be aware of:

1. Fan assist which gives the heaters an increased flow of the heated air and
2. A boost of additional power which can happen (depending on wiring) if the stored heat runs out before the next off-peak timing.

Fan assist is a normal feature and uses a small amount of additional power while in use. 
A heating boost can take significant additional power if engaged. 

There is no ‘offpeak meter’. There is a meter which records usage on its peak register during the daytime and on its offpeak register at night. 

I suggested you tell us a bit about your system.  This is what the manual for the Landis+Gyr E470 E7 meter says about the boost function:

So, using commands at the meter, it’s possible to switch power to the heater circuit outside of offpeak hours if necessary, e.g. during a cold snap when the heaters run out of steam early in the evening. Any electricity used outside the offpeak period will be charged at the higher rate.

I’d also like to remind readers that there is another type of Boost Mode at play - please do not confuse them as they are totally different.

Five-Terminal Smart Meters with Economy 7 functionality enabled often have a Boost Mode feature to enable the secondary load i.e. storage heaters/immersion heaters to run during Peak hours for a certain amount of time - but this is charged at Peak rates. When activated, the secondary load is energised for a pre-set amount of time before being de-energised again until either Boost Mode is triggered, or the Off-Peak hours kick in.

This is not the same as what a heater has on it.

Just to be clear, there is also a difference in wiring depending on what is used/required. 
The Boost from the meter uses the 5th terminal and switches power on for the pre-determined additional time. 
A boost switch on the heater requires a supply from the peak wiring circuit if used in that fashion but the result is similar in that power used is charged at peak rates 

Info all appreciated! I have a very early storage heater without fancy controls: so simple a child can operate. Only adults seek clarification about their operation! Rgds