PV inverter power loss

Hi all

I'm trying to figure out how inverter power consumption works in SAM for flat plate PV.

My simulation is giving me negative hourly energy at certain hours, so I'm assuming that is a result of inverter power consumption at night time. But how is this calculated? It's not just the inverter power consumption loss given in the results from what I can tell. For instance, during the first hour of operation, I get:

Hourly energy = -2.60568 (kWh)
Inverter night time loss = 329 (Wac)
Inverter power consumption loss = 2941.14 (Wdc)

Can someone please explain to me how they relate to each other? Inverter consumption starts off at 2941.14 Wdc but then drops during operation. The inverter's spec in SAM says 1815.26 Wdc during operation. So why is the inverter using more power at night when it's not doing anything than during the day?

Thanks.

Hello,
How SAM calculates the inverter's self consumption depends on the option you choose to model the inverter. For the "Inverter CEC Database" option, which I think is the option you are describing, the "Power consumption during operation" parameter on the Inverter input page in SAM is a nominal value. SAM calculates the actual hourly value as a function of the Sandia inverter model equation from King (2007) . In other words, the inverter's actual self-consumption depends on both the nominal value and the inveter's operating conditions.
The self consumption power also depends on the number of inverters in the system. The nominal value on the Inverter page is a nominal value.
Best regards,

Paul.