Monthly grid to load vs monthly use with system

Thanks. I didn't see this editor option before for this. Attaching now. 

Hi Nathan,

For the "Buy all / sell all" billing option, all of the power generated by the system is sold to the grid at the hourly or subhourly sell rate, and all of the load is supplied by the grid at the hourly or subhourly buy rate.

Can you tell me specifically what result you are concerned about in the file you sent me? Maybe I am not understanding your question.

Best regards,
Paul.

My main concern is the formula you posted, which makes total sense, does not align with numbers seen.

Electricity Use with System = Electricity Load - Energy to Load from System - Energy to Load from Battery - Energy to Grid from System

For January, we have the following: -4067=5403-1484-501-2125, which doesn't add up. There should not be an overly negative usage when PV doesn't even generate the total system load. 

Hi Nathan,

The "Electricity use with system" variable is not a very good indicator of grid power. It is intended to help understand the bill calculations for the net metering options where the billed electricity "usage" can be different from the physical grid power used to meet the load because of net metering credits. SAM doesn't actually use that variable for any calculations. For the buy all / sell all metering option it is set to minus "System AC energy".

The "Electricity to/from grid" variable is a better monthly output to use to see how the system is working regardless of the billing option.

Sorry that these variables are a bit confusing.

Best regards,
Paul.

Thanks, that seems to be a better variable to look at. Things are starting to make a bit more sense. I've watched the parametric videos on youtube to try and understand how to set things up, but I might be missing something. I've set up my my model from a single-run standpoint, specifying dc and ac capacity. Does this override any setup in a parametric run? I've set the desired PV dc array size to 20, 30, and 40 kWdc, yet the results are essentially the same for system dc energy for each run. 

Hi Nathan,

Please see this post on parametric simulations and PV sizing:

sam.nrel.gov/forum/forum-general/2808

Best regards,
Paul.