What should my control unit on off times be for best energy usage

It will depend on how much storage it has. There is a fair chance that it will need some topping up during the day or evening though.

Check what your 'low rate' times are on your electricity tariff. Your best bet will probably be to 'pre-heat' the house at the the 'low rate' e.g 4am to 7am then top up as required in the daytime depending on when you are at home. It may require a bit of experimentation to achieve the optimum result.

ideal times are your off peak times.

NT

If its off peak then you have to ask your energy supplier for that tariff and it is they who will tell you when they consider off peak to be, if that is not what you want and its not really a separate tariff, then it matters not when its on as you get charged the same. Brian

Which may vary rather a lot or very little depending on what sort of off peak time switch you have. A "teleswitch" should be fairly stable about when it switches and for how long it is on. A mechanical one will keep good time provided there is mains but power cuts can mess 'em up depending on how long the power cut is and how long the clockwork backup lasts. They can drift and give you off peak in the middle of the afternoon...

You really need to examine the meter/time switch and maybe observe when your off peak period actually is. I've never seen it on a bill and it would only be theoretical as well with a mechanical time switch.

I have recently moved to a house with teleswitched off peak heating. The supplier calls this "Total Heating, Total Control", but omits to point out that the "Control" is all in the hands of the supplier, ie the PES. I notice the system comes on overnight, and also at very random times during the day. I've also noticed that hot water and heating are controlled separately, through the same low rate meter. There are a limited number of other suppliers who will bill this system. I have changed to one which I reckon will save me about 6%. As I did in my last house, I'll continue to read the meters monthly and plug the readings into a spreadsheet, as this is the only way to be sure of what's going on. And of course it also means I can check my monthly DD to ensure I'm paying the correct amount.

E10 I think, gives you the 7 hours or so overnight and a further "boosts" during the day.

Compared to E7, E10 is very rare.

Dave, thanks.

According to SSE (for it is they!) my tariff is "Standard THTC". We'll see how things progress. On a bad day, SSE is a force to be reckoned with. I moved in May, and did a "best estimate" for what I should pay monthly to average out my payments. Two months later they sent my first statement, together with the "good news" that I was paying too much, and they were going to reduce my payments - by 26%.

Hardly surprising, in the middle of the hottest summer this country has had for years!