Intervening only on a single system (e.g. boiler room) often does not produce the desired effect because many other factors were not taken into consideration (e.g. conditions of use, temperature set points, etc.).
In such cases, you can look for a complete solution that integrates the entire system or building into one energy solution which minimizes energy consumption by gathering all relevant information (window openness, limitation of temperature set points, day and night mode, peak power management, etc.).
Under such conditions savings of about 20% are achieved, which of course depends on each individual case.