Electricity rates, energy charges with billing demand kwh/kw tiering question

Hi, We have a particular use case where we are analyzing total energy savings under two different rate schedules for a PV and battery system.
One is called schedule 6 which is simple energy + demand charges as described here .  This runs fine in SAM.
The other is schedule 6A which is tiered energy with billing demand kwh/kw, using current month kW along with simple off peak kwh charges (which happen to be negative) as described here .
There are several typos in the 6A download but in the end I believe energy charge table should look like the screenshot below .
However, SAM simulate fails with errors...from the log:
exec fail(lib_utility_rate_equations): The energy rate table defines 2 tiers, but one or more periods have 1 tier. All periods must have the same number of tiers.
Simulation pvsamv1 failed :exec fail(lib_utility_rate_equations): The energy rate table defines 2 tiers, but one or more periods have 1 tier. All periods must have the same number of tiers.

I have tried various combinations of adding duplicate rows to get two tiers for periods 1 and 3 but SAM always throws errors related to Max Usage Units.  

Can SAM team recommend the correct way to enter the 6A rate schedule?

 

Hi Peter,

When using images in posts on this forum, please use the Attachments button to attach a image files (you can then insert them into the message if you want) instead of copying and pasting the image into the forum editor. The latter approach does not always work reliably.

When using data from the OpenEI Utility Rate Database, it is always a good idea to compare the data imported to SAM with the data on the OpenEI website as you are doing, but also to compare the data to the actual rate sheet from the utility company. There is always plenty of opportunity for error (or misinterpretation) when working with rate data.

I could not see your screenshot, but here is an example of an energy rate structure that causes that error:

 

To fix the error, you could either add a second tier to Period 2, or remove Period 2.

For the 6A rate schedule in your example, you could define the rate table like this (use this as an example, please refer to the OpenEI data and rate sheet to get the correct numbers). For the periods with a single tier, I used two tiers with the same rate:

 

 

Note that I added up the rate and adjustment values from the OpenEI table because SAM does not have separate columns in the table.

When you run a simulation in SAM, be sure to look at the results on the Data Tables tab under "Electricity Rate Data by Tier and Period" to check that SAM is calculating the rates as you expect.

Best regards,
Paul.