Electricity Rate adjustments for rate change mid-month

Hello,

I live in Arizona and use Salt River Project for electricity. I am exploring my PV options and running simulations on various configurations.

I imported rate schedules from the OpenEI database for E-13 and E-23 Rate Plans via SAM's Electricity Rates page. These plans have seasonably adjusted rates. The data I see in SAM appears to accurately represent these plans except for an important detail. According to SRP's rate schedules:

Summer is defined as the May, June, September and October billing cycles. Summer
Peak is defined as the July and August billing cycles. Winter is defined as the November
through April billing cycles.

I spoke with an SRP representative for clarification and learned that the rates are based on the last day of each billing cycle. For example, my closing date is the 5th of each month. My July bill will be based on energy use from June 6 through July 5. SAM will calculate billing using Summer rates for 6-30 June plus Summer Peak rates for 1-5 July. SRP will bill me using Summer Peak rates for the entire period.

Is there any way to adjust calculations to be based on billing month rather that actual calendar month?

I'm a retired software engineer with over 5 decades of programming experience. I am open to suggestions on how I might do this myself.

Thanks

Hi Steve,

SAM's electricity bill calculations are based on calendar months. It is not possible to change the start and end day of the month. This approximation should be good enough to make the kind of high-level decisions about system size, battery dispatch, etc. that SAM is designed for.

The source code for the electricity bill calculations is here: github.com/NREL/ssc/blob/develop/ssc/cmod_utilityrate5.cpp

An overview of the SAM code repositories is here: github.com/NREL/SAM and here: sam.nrel.gov/about-sam/sam-open-source

Instructions for building your own version of SAM from the open source repositories are here: github.com/NREL/SAM/wiki

Instructions for contributing code to SAM: github.com/NREL/SAM/blob/develop/CONTRIBUTING.md

Best regards,
Paul.

Thanks Paul,

Before I learned about SAM, I used the PVWatts Calculator web appblication to simulate energy production and used the generated csv file as input to my own Python scripts. I wrote some Python classes to model billing specific to SRP's rate plans which account for the shifted rates schedules.

After posting my original message here I realized that I could export "generated_power.csv" from a SAM simulation and use those data with my own python scripts.

Since I am using this to make decisions on installing Solar on my house, I may just take this approach rather than trying to make SAM do what I want. I do really appreciate that all of the simulation outputs can be exported from SAM and that it has libraries for a broad range of PV system components.

Best regards,

Steve