Hi @Mariafa ,
You’re comparing apples and oranges here:
When you use district systems in OpenStudio, the energy use that you get out is the thermal energy of the hot and cold water (effectively, you’re externalizing the whole heating and cooling plant from the EnergyPlus calculation). Conversely, the energy use of a heat pump is electricity. So, if your heat pump is producing hot water and has a rated COP of 3.3, the energy use of the district system will be 3.3 times that of your heat pump when it’s operating at its rated conditions. Clearly, in your case, it’s not operating at these rated conditions all of the time, which is how you end up with 2 times the energy use instead of 3.3 times.
Does that make it clear what is going on?