When your talking about hot water, I assume you are talking about domestic hot water i.e. showers, taps etc. Our house has undefloor water heating so it’s important to differentiate these two…
When it comes to domestic hot water, you can really optimize the heating of it if and only if you have sufficiently big tanks. Our ground source heat pump has a 180 liter tank but in addition to this, we have a 300 liter boiler so the total capacity is 480 liters. This is easily enough for our household for more than 2 days. So in our case I can easily heat the domestic hot water when the electricity is cheapest. Our Nibe ground source heat pump can produce logs to an USB stick so I have learnt that it takes about 1 hour per day to heat the domestic hot water. The boiler usually takes 1.5 hours so I find the cheapest 2 hours and use those to heat the water in the boiler.
When it comes to heating the house, overheating today because tomorrow is expensive is most probably going to cost you more money than what you can save, unless you have very, very thick concrete floor which can preserve the heat very well. The air in the rooms does not preserve the heat almost at all so it’s just pure waste of energy until you can store it somewhere.
I’m about to release a new version of the heating optimization algorithm in the next coming weeks which is by far the best I’ve had so far. That uses a bit of overheating if the weather forecast says that there is going to be a big temperature drop. So instead of being reactive and waiting the temperature drop, the algorithm increases the calculated heating need before the temperature drops. And obviously uses the cheapest possible hours to do so. I’ll inform about this new release in this thread when it’s available:
Cheers,
Markus