Estimate how long thermal storage associated with a heat pump system can support a steady heating or cooling load. Enter usable stored thermal energy, the average thermal load, discharge efficiency, and an operating reserve. Results separate deliverable energy from losses and reserve, helping you check peak-shifting or backup-duration assumptions.
Duration is the time a store can support the entered constant thermal load before reaching the reserve. If load varies significantly, a single average can hide short peaks, so model intervals separately.
This calculation applies to an explicitly defined thermal store. Ground loops and the surrounding earth require transient thermal modeling and should not be treated as a fixed-energy tank without an engineering model.
A 60 kWh thermal store at 90% discharge efficiency with a 10% reserve delivers 48.6 kWh. At a 8 kW load, estimated duration is 6.08 hours.
It models a thermal energy store supporting a constant load; it does not treat the ground loop itself as a simple battery.
A reserve represents energy intentionally left unused for operating limits or resilience.
Only if your entered efficiency is selected to include them for the modeled discharge period.
Use a time-weighted average load or calculate separate operating intervals.
No. Capacity and load must both use compatible thermal energy and power units.
| Input | Required basis |
|---|---|
| Stored energy | Usable thermal kWh before efficiency and reserve |
| Load | Average thermal kW during discharge |
| Efficiency | Fraction delivered from storage |
| Reserve | Fraction intentionally retained |