Hot water demand in your PartL project is calculated through the NCM databsase.
From the NCM modeling guide:
"For hot water the energy demand must be taken as that required to raise water temperature from 10°C to 60°C based on the demands specified in the activity database. The activity database defines a daily total figure in l/m²/day. If users of DSMs wish to distribute this demand over the day then the daily total should be distributed according to the occupancy profile"
The SBEM calculation engine calculates the hot water demand based on activity type and floor area of the relevant space. Setting occupancy levels will not effect the hot water consumption levels. Note that some activity types can have a relatively high HWS requirement; for e.g. Changing facilities in training centres.
Further consideration; If you are find that modifying your HWS system, or adding a solar system to the HWS generator for a zone but not seeing changes to results, this could be that you have the system assigned to a zone that has no requirement for a HWS system. For e.g. A residential care home, HWS systems should be assigned to zones containing Bedrooms rather than zones dedicated to Bathrooms.