Rate structure with Demand charges over base KW per month

  • sfccsolar
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10 Feb 2013 02:20 #1262 by sfccsolar
Rate structure with Demand charges over base KW per month was created by sfccsolar
PNM NM has commercial rates with "special" features. Its not clear if SAM can handle this or what if any workaround there is. Or perhaps using the SDK which is its own project.

E.g. Rate 4B, which doesn't seem to download properly from OpenEI,org into the tables, has Demand charges OVER a certain base for the customer (500kw). If you have a peak in the billing month of 1500kw, then charges are say $10/kw over 500kw so in this example $10,000.

Using hourly or (15min) data for KW is clearly overestimating the costs, as expected.

Additionally - is there any detailed description of the handling of Savings estimated, of the PV in a 'peak shaving' contribution during the solar resource window? I think PNMs peaks are only counted in the "on-peak" 8am to 8pm time period. Does the program actually recalulate the NET kw-peak/month, accounting for the solar contribution in each time bin.

I assume if it does, the 15 min data comes much closer the actual peak (if the hourly data is an average kw peak/hr)

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  • Paul Gilman
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11 Feb 2013 21:55 #1263 by Paul Gilman
Replied by Paul Gilman on topic Rate structure with Demand charges over base KW per month
Could you please spell out the acronyms PNM and NM so that I can test the utility rate download?

SAM does not model the type of demand charge you describe. You can specify a fixed $/kW amount, but not as a difference between the peak demand and a base value.

In the "peak shaving" scenario you describe, how is "on-peak" defined? In SAM, the peak demand for a given month occurs in the time step for which the load kWh (over the time step) is the maximum for the month.

Best regards,
Paul.

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  • sfccsolar
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11 Feb 2013 23:07 #1264 by sfccsolar
Replied by sfccsolar on topic Rate structure with Demand charges over base KW per month
Certainly
In the Utility database it appears as
Public Service Co of NM (New Mexico)

It didn't appear to address this demand charge by design to either.

PNMs Rate 4B uses an 8am to 8pm On-Peak billing rate and demand charge window.
I did not enter the KWH hourly data in the first test - just hourly demand data
I wasn't sure if it would do an average kw/hr to arrive at kwh / hr.

Should I use the normalize function here ?

I guess our results won't be accurate even then due to PNMs type of demand charge


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  • sfccsolar
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11 Feb 2013 23:10 #1265 by sfccsolar
Replied by sfccsolar on topic Rate structure with Demand charges over base KW per month
I also added the PNM Rate schedule 4B
in case its of interest.

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  • Paul Gilman
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25 Jul 2013 19:38 #1266 by Paul Gilman
Replied by Paul Gilman on topic Rate structure with Demand charges over base KW per month
Hello,

The Beta version of SAM (SAM 2011.7.12) includes a reworked Utility Rate page that downloads rate data from the new Version 2 of the National Utility Rates Database . The Utility Rate page in SAM 2013.1.15 and older versions worked with Version 1 of the database.

The new version can represent rate structures like the Public Service Company of New Mexico Rate No. 4B that have a tiered-time-of-use demand charge. I tested the rate import function in SAM, and the rate structure seems to import correctly:

A (Customer Charge) imports the PNM Owned Transformer charges as a single fixed monthly charge because SAM does not have inputs for separate monthly charges:

Fixed Monthly Charge = ( $8,735 * 3 months + $7,100 * 9 months ) / 12 months = $7,508.75

B (On-peak Period Demand Charge) again imports the PNM Owned Transformer charges for billing demand above and below 500 kW during on-peak hours to the Time of Use Demand Charge inputs at the bottom of the Utility Rate page:

Period 1 (off-peak) Demand Charge = $0/kW
Period 2 (on-peak Jan-May, Sep-Dec) up to 500 kW Demand Charge = $0/kW, over 500 kW Demand Charge = $14.2/kW
Period 3 (on-peak Jun-Aug) up to 500 kW Demand Charge = $0/kW, over 500 kW Demand Charge = $17.47/kW

C (On-peak and off-peak Energy Charge) imports to the Energy Charge inputs:

Period 1 (off-peak) Energy Charge = $0.03658/kWh
Period 2 (on-peak Jan-May, Sep-Dec) Energy Charge = $0.05531/kWh
Period 3 (on-peak Jun-Aug) Energy Charge = $0.07043

This assumes that there are no power factor adjustment charges (D) and does not account for other applicable riders (F) or special tax and assessment adjustments (G).

Note that the rate sheet defines on-peak hours as applying to Monday through Friday, so the on-peak periods are not on the weekend matrix in on SAM's Utility Rate page.

Also, I've only copied the visible digits from the Utility Rates page in the values I show above, but SAM imports the full values. For example, the Period 1 Energy Charge appears to be 0.03658, but if you click in the cell and use the right arrow key to scroll to the end of the number, you'll see the full value of 0.0365815.

I've attached a SAM file (Beta version 2013.7.12) to your original post that shows how the new version of SAM correctly imports data for that rate sheet.

We'd really appreciate your feedback on the new Utility Rate page in the Beta version. If you have time, please download the Beta version from the Downloads page and let me know if you have comments.

Best regards,
Paul.




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