Allow compensation rate within TOU tiers

[steverep]

Is your feature request related to a problem? Please describe.

SAM currently only allows a flat compensation rate that applies for net metering. From the documentation:

For the purpose of annual net excess compensation, monthly excess generation is calculated from the monthly total generation and load, regardless of time-of-use (TOU) periods.

PECO has net metering, but on their TOU rate plan, the annual cash out is done at the "price to compare" within each TOU tier. See https://www.peco.com/cdn/assets/v3/assets/blt1b5616c79bacadb4/blte7bf67602d7799ef/64cb648f5b39c52180713adf/S1-Solar_Net_Metering_Time_of_Use_10212021.pdf?branch=prod_alias.

Describe the solution you'd like

It would be helpful to be able to specify the compensation rate within the same tiers that are used for electricity charges from the grid. SAM seems to already bank everything separately, so I hope this would be a straightforward improvement.

Describe alternatives you've considered

Using one of the other compensation types (e.g. net billing or net metering with $ credits), but I don't see a way to accomplish it (at least certainly not simply).

[brtietz]

@steverep thanks for filing! I agree there isn't a good way to model this cash-out structure in the current software. Are you aware of any other utilities with this cash out structure? That'll help inform whether we add another option directly under "metering and billing" or implement a checkbox more similar to the roll-over credits.

[steverep]

I'm not aware of others, but I'm really only familiar with PECO. I would suspect that other Exelon companies and/or other PA utilities might have the same structure.

A simple checkbox wouldn't work though as the cash out rate is not the same as the meter rate. The meter rate includes distribution charges, whereas the cash out rate is just the generation charge. I guess the checkbox could just turn the flat rate input into a matrix though if that's what you meant.

[steverep]

Just out of curiosity I checked how PPL handles net metering with TOU pricing. It's unclear from the documentation I found whether they pay out the banks at different rates, but they also have a policy of using the banks that is also hard to model in SAM. It appears they may pull from a peak bank to offset off-peak hours within any given month.

[steverep]

Checked the TOU plan for Duquesne (DLC) today, and they also cash out based on the TOU period like PECO. However, they apply excess credits to a given bill like PPL, which again also cannot be modeled in SAM AFAIK.

[brtietz]

This is enormously helpful, thanks for adding those links to the issue. I'm meeting with some folks on the URDB team next week and will bring these up at that meeting.

[steverep]

No problem 👍🏻

As an aside, PECO's residential rates in the database are wrong. They are bookkeeping over 5¢ of adjustments in all the rates, but in reality all of those are baked into the price except for the transmission service charge and the distribution charge.