Using The Hot Water Tank As Energy Storage

Feeding surplus solar power into the grid pays badly at our tariff, so using it ourselves is clearly the better option.

My current experiment: treating the hot water tank of the heat pump as an extra store for that surplus. Water holds heat well, and we need hot water anyway.

An automation sets the target temperature of the tank depending on how much the panels are producing at that moment. All the data sits in Home Assistant and the heat pump can be controlled remotely, which is what made this possible at all.