[evandev]

With an air to water heat pump, you typically add a buffer tank that among other things helps keep preheated water warm. It is basically a hot water tank so doesn't last through the night

However for other hydronic applications such as solar water heaters there is typically a thermal storage tank which can help store heat like a battery.

Keep in mind a few things. One is some heat pumps are now operating down around -22*F. Second is geothermal is a water to water heat pump that isn't affected as much by the limitations of air temperature (but has other limitations). Third is radiant heat flooring with tubes in concrete acts as a thermal storage tank. Finally heat pumps for heating work best at low temperature hydronic water and can also be used for other applications such as DHW (domestic hot water) which needs to be at slightly higher temperatures than a buffer tank has.