Using a Digital Twin to Cure Hospital’s Energy Waste and Elevate Patient Care

The main mission of any hospital is healing. However, this core purpose often clashes with the harsh reality of operational costs. Have you ever asked yourself what the hidden cost is of prioritising human comfort ahead of operational efficiency? In a large Slovenian General Hospital, management faced an impossible balance. The main conflict was straightforward: the hospital’s heating and cooling controls were too slow, forcing staff and patients to open windows when rooms became too hot. But how do you maintain an ideal therapeutic environment, where staff and patient comfort is a priority, while simultaneously reducing the immense financial burden of energy waste? 

With prior, traditional efforts having no effect on this deeply ingrained operational failure, the hospital needed to move beyond “please, close the windows” emails and implement a solution that provided data-driven accountability for every euro lost. That’s when GreenTwin was brought in to provide the objective, verifiable cure.

The Vow vs. The Leak

Hospital management is always driven by two critical, often conflicting, demands: 

• Patient outcomes 
• Fiscal responsibility

In the Slovenian hospital, this conflict was expressed through pure waste. Because the building’s radiators were incorrectly set, valves were often left wide open. The only way the staff could adjust an overheated room was to open a window. This created an operational failure where energy conservation became a suggestion, not a strict policy. The management knew the problem was serious, but without any way to prove or track the exact financial loss caused by this behavior, they couldn’t justify the necessary investment. The challenge was that massive energy waste was hidden in plain sight within the core need for patient comfort, making it an impossible cost to cut.

The Challenge: Accountability Without Conflict

Everyone can fix a radiator. But this is just a temporary fix. The real challenge was creating a long-term system that enforced accountability without conflicting with patient care. The hospital needed to quantify the double-loss scenario:

1. The unnecessary expense of overheating patient rooms (and, as a result, lowering the comfort of both staff and patients)
2. The catastrophic heat and energy loss from windows left open while cooling was running

Without clear data, their annual HVAC budget was completely exposed to human habit and guesswork.

The Solution: A Data-Driven Cure

The solution started at the source: GreenTwin built a new digital data layer over the existing infrastructure to capture the reality of the thermal environment. By working on one of the hospital’s nine buildings, the team installed a strategic network of sensors, focusing on the points of conflict:

• Window Sensors: to track the status (open/closed), the duration, and the frequency of window openings
• Temperature Sensors: to record internal and external temperature fluctuations
• AC Monitoring: to measure A/C control switch status and power consumption

GreenTwin’s smart network turned the physical building into a constantly learning digital asset. For two months, we measured the data, creating an evidence-based digital twin that exposed the dynamic losses. Using advanced algorithms, the system could perform a dynamic loss calculation that proved the financial drain:

1. Overheating loss: the system calculated the temperature difference between the real, high room temperature and the optimal setpoint, measuring the energy waste due to incorrect radiator settings that caused excessive temperature difference between inside and outside temperature. The bigger the difference, the bigger the loss.
2. Ventilation loss: by calculating the necessary ventilation time for the room and subtracting it from the actual window-open time, GreenTwin isolated the pure loss caused by leaving windows open unnecessarily while heating or cooling was active

To guarantee credibility to the management, GreenTwin applied a 60% safety factor to the measured losses before extrapolating the data. This rigorous evidence allowed the hospital to scale the verified data across its entire campus, predicting a total annual potential savings of €317,000 – approx. 16% of their entire heating and cooling budget.

The Cure

But this was not the end. The data was the justification for the cure. The hospital used GreenTwin’s analysis to immediately implement a zero-tolerance, automated policy that permanently solved the root cause of the waste.

First, they installed thermostatic radiator valves that are managed directly by GreenTwin. This allowed the hospital to set specific, optimized thermal regimes tailored to the room’s function (e.g., patient rooms are set to a comforting 22°C, while archives are reduced to only 16°C). What’s more, if staff attempt to manually override this optimal temperature, GreenTwin instantly resets the valve to the default policy.

This centralized control provided an additional benefit: Intelligent Anomaly Detection. The system can now identify waste without dedicated window sensors. For instance, if the room’s setpoint is 22°C, but the actual temperature drops dramatically to 16°C, the system instantly alerts that a window is open. Similarly, if the temperature inexplicably rises to 24°C during the heating season, the system will recognise that the staff is using unauthorized heaters.

Conclusion

The GreenTwin project proved that the path to massive energy savings is not always through replacing machinery or hardware, but through data-driven policy and precise automated control. By eliminating the need for manual intervention, the hospital is on track for the projected annual savings of €317,000. Moreover, since implementation, zero complaints about room temperature have been registered. The system delivered a 16% reduction in OpEx while simultaneously fulfilling the core mission: ensuring a consistent, therapeutic environment for patients. The vow of healing and fiscal responsibility has been fulfilled.