DHW To Reheat or Schedule? What's the most economical?

Unfortunately we don’t get a cheaper tariff at night. On my controller it has “Reheat Temp” it is set at 40. Does that mean when the tank temp drops to 40 it will reheat, or does it it will reheat to 40 when the tank temp drops to a certain temp. In the first scenario what temp would it reheat too, how would I control this? In the second scenario how would I control the temp it drops to before reheating? We do have solar and an  i boost which is great for heating the water. Unfortunately we don’t get much sun in the Highlands, especially Oct to April.

Hey @Boots and Bens,

Moved this topic into the ‘smart home’ category so it get’s more traffic. 

Just tagging in some fellow heat pump users to see if they can help @Chip370 @Nick Challacombe @Old Timer @RAJ @christianedward @M.isterW 

I believe that reheat is more efficient but that's just anecdotal. However, if you have a tariff that offers cheaper electricity at certain times of day that makes it more economical to schedule the water heating. There are loads of tariffs that offer this so it's worth shopping around, particularly if you also have a battery.

If your reheat temp is 40, when the water around the sensor reaches that temp the heat pump will heat the cylinder back to your chosen temp (that is normally 50 or 55). Remember it only takes the temperature from a single place in the cylinder so you might have plenty of hot water even when the sensor is reading low.

Thanks, I maybe will lower the reheat temp to 30.  No reduces tariff with So Energy. What can you tell me about batteries? I am guessing they are very expensive and you need to live somewhere very sunny for them to be economical?

That's a good reason to move to a different energy company.

Batteries are pricey but you don't have to be in a sunny place for them to be worthwhile. It depends how much electricity you're generating. We are mostly self sufficient in the summer because the battery gets us through the night. In the winter it allows us to use all of our generated electricity instead to sending some to the grid. I sometimes charge the battery on cheap rate electricity to get us through the expensive periods, which saves us money. If you want to make your battery work harder, there is at least one tariff on the market that actively encourages you to charge your battery when there's excess electricity and discharge it to the grid at peak times. So there are plenty of ways to make it financially viable.

This excerpt from the Daikin manual explains schedule +reheat. The hysteresis value is 10 degrees by default so when the tank temp falls below reheat - hysteresis (40-10=30 in my case) the reheat function is triggered. 
The example of 60 deg for hot water is unnecessary high ! Mine’s at 49.
You also have to bear in mind that the heat pump can only do one thing at a time so the space heating goes off when it’s doing the hot water. 
 

@Boots and Bens if you set reheat to 30 it’ll only ever come on when the tank drops to 20 !!

Ok so set at 40 it will reheat at 30, why the 10 degrees difference, what the point in setting for a reheat temp you want and then it does not do that until it is 10 degrees below that?

?  You say it will heat up to whatever the set temp is, is that the set comfort temp or eco temp? Or is a temp that cannot be changed?

Sorry dont really understand the graph I do have the manual with that in, what to the  shower symbols mean, when a person showers.  We don't use the shower that often, at most once a day one person and a couple of days a week not at all. Probably use more water for washing up. So my thinking was if I changed the set reheat temp form 40 to 30 then it would not heat until it dropped to 30 and hence not as often, Thank you very much for advise and patience