Billing demand lookback with TOU "Included in Billing Demand" of zero causes unexpected results

[cpaulgilman]

Describe the bug

See https://sam.nrel.gov/forum/forum-general/4849-billing-demand-potential-discrepancy.html

billing-demand-lookback-issue.zip

The attached default PV / Commercial is modified to enable billing demand lookback and set "Included in Billing Demand" in the Billing Demand by Time-of-use Period for Demand Charges table to zero:

This causes unexpected billing demand with system results.

Consider adding SSC error check to display error when Billing Demand by TOU table has no TOU periods included in billing demand. Suggested message:

"The ur_dc_billing_demand_periods matrix must include at least one TOU demand period from the ur_dc_tou_mat matrix."

Note that this is required even when Charge ($/kW) in the TOU Demand Charge table is zero for all periods.

To Reproduce

1. Open attached .sam file (see above).
2. Run simulation.
3. On Data Tables tab, under "Electricity Rate Data by Year," click Billing demand with system (kW) and note billing demand in Years 2 and later is set to minimum billing demand of 100 kW.

Operating System and Version

Tested in SAM 2024.12.12 and SAM 2023.12.17 r2

Windows 11

[cpaulgilman]

Help revision for SAM 2024.12.12 r1 with note to explain requirement:

[brtietz]

Help revision for SAM 2024.12.12 r1 with note to explain requirement:

That note text looks great, thank you!