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A HoCoSto storage is an underground energy storage facility. Energy is stored in water (storage medium), this water is heated or cooled allowing energy to be transported into or out of the storage.

The thermal energy, usually heat, is pumped from the HoCoSto storage to a TSA (heat exchanger) where it releases its heat to the heat consumer. A HoCoSto thermal storage unit can be used at temperatures from 5 °C to 90 °C. Within this temperature range, heat storage has an energetic content of 98 kWh per m3 of water.

The HoCoSto has insulation, waterproof foils and protective cloths on all sides. An aluminum space frame is placed in the storage. This frame gives the storage its carrying capacity to cover a this one. Once this deck is backfilled with a layer of soil, the land above it is usable again. This could include a lawn, a playground or even a parking lot.

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  • Source peakshaving: Here, heat storage is used to allow the heat source to produce heat as efficiently (or cheaply) as possible, or to resolve irregularity on the heat source side
  • Load peakshaving (Load balancing): This involves using thermal storage to handle peaks on the demand side. This has the advantage that all system components can be interpreted to average usage. Peaks on the demand side are met by storage.

Seasonal storage

Here heat storage is used to store sustainably generated energy in the summer for use in the winter. This is often done i.c.w. PV panels or solar collectors as an energy source. Seasonal storage is generally larger. Peak and seasonal storage can also be combined in one system. This avoids the need to purchase electricity at expensive times.


The heat pump combined with the buffer water can be used to produce cooling in the summer. The resulting waste heat is stored back in storage and used as heat.

Hot water and tap water

Through the heat network and delivery sets, both hot water and domestic hot water are delivered to the building or homes.