Electricity bill escalation rate: value mode vs. schedule mode discrepancy

I am modeling a project that requires the electricity rate to change by different percentages in different years, so I would need to use the electricity bill escalation rate in schedule mode. However, I have found that the schedule mode is giving different results than value mode, even though I have tested using the exact same rate in both.

For example:
Test case 1:
Inflation rate: 2.5%
Electricity bill escalation rate (value mode):  -0.7% real (1.8% nominal)
NPV: $513

Test case 2:
Inflation rate: 2.5%
Electricity bill escalation rate (schedule mode):  1.8% every year
NPV: $-33,073

All other parameters are identical between both models. Theoretically, shouldn't the results be identical even though I am using value mode in Test 1 and schedule mode in Test 2?

I have attached the test file. Any assistance is greatly appreciated!

Hi Evan,

The calculations for "schedule mode" are described in the "Edit Table Data by Column" topic in Help, in the "Window Reference" section: samrepo.nrelcloud.org/help/edit_data_table_column.htm

See the attached .sam file and Excel workbook with details about these calculations.

Best regards,
Paul.

Hi Evan,

I think your point is valid since you just change one parameter and keep all the others identical. This way it could show which option (between the 2) works best. 

The only thing I can think of is there might be other parameters to include in your model to get more accurate results.

I hope this helps

Hi Paul,

Thanks for this info; it was extremely helpful!

I am attempting to add an input to the "Send to Excel with Equations" spreadsheet that would allow a user to input the rate escalation among all of the other inputs on the "Inputs and Outputs" sheet. However, I am realizing that the "Electric load annual growth rate" also has an effect on the results of this escalation equation.

I was hoping for some advice on implementing this feature in the excel workbook. If the load annual growth rate stays constant throughout the analysis, I assume that it shouldn't be too hard to figure out an equation, but I can't seem to figure it out.  Any thoughts would be appreciated!

Hi Evan,

For the Residential and Commercial financial models, SAM exports the annual "value of energy savings" to Row 97 of the Inputs and Outputs worksheet because the electricity bill calculations are too complicated to replicate in Excel. Because the effect of load growth is accounted for in SAM's internal calculations, I don't see an obvious way to make it an input to the spreadsheet.

Best regards,
Paul.