My solar PV system, produces a significant amount of unused electricity.
I have a Thermal store based heating system .... providing mains pressure DHW off one heat exchanger and underfloor heating from the other ... the water content of store being circulated around the boiler when heat demand is called.
A consideration is to install a 2nd hot water cylinder, and use the excess PV power to feed an immersion heater .... creating a large store of heat.
Any call for DHW will result in thye incoming cold mains being pre-heated by this store .... when store is depleted, the normal heat exchanger function within the Thermal store would maintain DHW supply, topped up if necessary by boiler.
I did ask a few weeks back about just using Solar PV excess direct into Thermal store immersion, but as this is kept 'at temp' don't really see a way to easily do that.
This pre-heat method would seem a suitable alternative ... and using the mass of the water as an energy store.