Understanding TSOL report: "DHW heating energy requirement" vs "Annual energy requirement"

[Koffi]

I am using TSOL with configuration A7.1 - DHW thermosyphon system with electric water heater to model a thermosiphon system. In the simulation report, I am trying to understand what "DHW heating energy requirement" and "Annual energy requirement" represent.

Observations:

• For large loads, both values are displayed and are equal, and in some cases they are different but nearly equal

• For smaller loads, the "DHW heating energy requirement" disappears from the report entirely. Only "Annual energy requirement" remains

My questions:

1. What do these two fields actually represent? The difference does not appear to be losses, since losses are reported separately elsewhere in the report.

2. Why does the "DHW heating energy requirement" field disappear for lower loads? Is there a threshold (e.g., solar fraction > 95%) that changes the report format?

Thank you for any insights.