Demand costs not included in Electricity bill when there is excess credit

Hi,

I am modeling a 4 part rate with a NCP and TOU demand charge, as well as TOU energy charges. I noticed when running the macro "Value of RE" that the Total Bill is not the sum of the individual components (i.e. fixed, energy, demand). This impacts both the Year 1 and PV of Annual Costs, as the savings compared to no system calculation is based on the incorrect total bill, which in turn affects the NPV of annual costs.

When I looked into the individual simulation, I noticed that the demand charges are not included in the Electricity Bill category (which appears to correspond to the Total Bill value in the macro) when there is an excess energy credit. This can be seen by looking at the monthly data table. In the attached file, the January charges for TOU demand ($28.3075), flat demand ($20.1095), energy ($28.4054), and fixed ($10.25) all add up to the electricity bill ($87.0724). But in March, when there is excess generation, the TOU demand ($22.2725), flat demand ($15.8223), energy ($0), and fixed ($10.25) does not equal the electricity bill ($10.25). It appears that in this case, the demand charges are not included in the electricity bill calculation.

This does not appear to occur in a energy-only TOU rate.

Separately, the summary report of the "Value of RE" for energy only TOU is a bit misleading. In this case, the total year 1 energy is $209, and the total year 1 fixed is $150, but the Total bill is $331. This is correct, because there is a $28 credit left at the end of the year that balances this, but the result table does not make this clear.

Thanks,
Kevin

Hi Kevin,

Thank you for reporting this issue.

I think the problem only applies to the "Value of RE" macro with the "Monthly total excess credited to next month bill in $ at sell rate(s)" option, when the total PV generation exceeds the load for one or more months.

We are investigating, and I will get back to you when I have more information.

Best regards,
Paul.

Hi Kevin,

We have fixed this problem and will include it in an update patch we hope to release in the next week or so.

github.com/NREL/ssc/issues/118

Thanks again for bringing it to our attention.

Best regards,
Paul.