Can hot water store excess solar energy?
Yes. A water heater can shift some electricity use toward solar hours by preheating within safe temperature and equipment limits. The tank stores thermal energy for later hot-water demand.
Why a heat pump changes the math
A resistance element turns electricity directly into heat. A heat-pump water heater uses electricity to move additional heat from surrounding air, so it can often deliver substantially more heat per unit of electrical input. Site temperature, space, noise, condensate, recovery rate, controls, and installed cost still matter.
When dedicated PV resistance remains interesting
The PVDHW concept becomes more relevant when the system is off-grid, DC coupling simplifies a specific project, thermal storage is inexpensive, or PV energy would otherwise be curtailed. It should be compared against flexible grid-connected operation—not assumed superior.