NEM Aggregation (SCE)

[gvl]

I've been trying to understand how billing works for accounts with different TOU rates aggregated under NEM. Multiple calls to SCE proved to be an exercise in futility. This is a description of how billing works:

Billing Methodology
SB 594 requires a proportional allocation billing methodology that must be computed
monthly. SCE will bill each metered service account participating in NEM
Aggregation individually, according to the billing provisions applicable to all NEM
customers. However, for accounts participating in NEM Aggregation (which will all
be placed on the same billing cycle), the energy consumption (kWh) registered on
each account’s meter will be reduced, for NEM billing purposes, by a proportional
allocation of the energy that is generated by the Renewable Electrical Generating
Facility and exported to SCE’s grid, as registered on the meter of the service
account directly interconnected to the Renewable Electrical Generating Facility. For
example, if the account directly interconnected to the Renewable Electrical
Generating Facility consumes 50 kWh, aggregated account #1 consumes 150 kWh,
and aggregated account #2 consumes 200 kWh (making the total consumption of
the NEM Aggregation arrangement 400 kWh) , the directly interconnected account is
allocated 12.5 percent (i.e., 50/400 kWh) of the energy exported to SCE’s grid by the
Renewable Electrical Generating Facility, aggregated account #1 receives 37.5
percent (i.e., 150/400 kWh), and aggregated account #2 receives 50 percent (i.e.,
200/400 kWh). SCE will require that the customer designate one account in the
NEM Aggregation arrangement to receive any remaining kWh not allocated due to
rounding after the proportional allocation described above is completed.

Since an NEM Aggregation arrangement (which consists of the account that is
directly interconnected to the Renewable Electrical Generating Facility and all
aggregated accounts) may include a mix of residential, commercial and/or
agricultural accounts, and, therefore, time-of-use (TOU), non-TOU and tiered rates,
all accounts in an NEM Aggregation arrangement will be metered at the 15-minute
interval level and the exported generation will be proportionally allocated in kWh at
the 15-minute interval level.

Say I have two accounts/meters A1 and A2, and solar is on A1. The solar system is sized for both accounts so that A1 will normally be a net producer. Does the above imply that in this scenario all energy that was exported to the grid in a particular billing period will be allocated to A2? Or does it mean the allocation will be based on the actual consumption as seen by the meter which is never 0 due to usage that exceeds solar output such as at night, so some generated energy will still be allocated to A1? Additionally it is not clear how credits are calculated for A2, is it done using A2's TOU rate in this example? I would think so.

My actual problem is that I need to decide whether or not it will be beneficial to aggregate my household and my EV charging meter under the NEM agreement. Yes ditching the EV meter and charging the car from my home meter would simplify things a lot, but I want to understand how aggregation works first before making the final decision.

[inetdog]

My reading of your quote (and IANAL) is that any surplus generated by A1 at any time period during the billing cycle will be allocated between A1 and A2 based on the import billing associated with that meter. And both the export and import numbers are the value of the real time import and export counters in the meters, not the net value at the end of the billing period.

If both A1 and A2 import 50kW and A1 produces an export (not NET export) of 40kW, then 20kW of export is credited to A1 and 20 to A2.
If A1 does not have any import at all, then all of the export credit will go to A2.
If A1 has a net import of 10k on its own, then it will not be as simple as allocating the entire export to A1 only.

It certainly will make a difference if you have a net surplus over the two accounts or if you have TOU or EV rates in the picture for the two metered services.

[sensij]

Here is a screenshot from their FAQ that is applicable to your question:

SCE.JPG

Keep in mind allocation is done on 15 minute intervals. At night, all of your accounts are net consumers, so all usage is valued at whatever the TOU rate is for that time period.

During the day, if you don't aggregate, let's say you are on TOU-D-A. If you generate 1 kWh over a 15 min period on-peak in summer, that would be credit worth $0.46. If you do aggregate, that 1 kWh will be proportionally split between the accounts. If the proportion is 50%, 0.5 kWh would be worth credit under the TOU-EV-1 plan, ($0.36267 * 0.5), and the remaining would be a credit for the original plan, or ($0.46 * 0.5).

Based on my experience on trying to figure out the proportioning scheme for TOU-D-T, it won't make sense without looking at an actual bill, with no disrespect toward the logical explanation inetdog offered. The example provided in the link above doesn't provide enough detail to be sure I understand.

You could probably make the decision without fully understanding the proportioning. Just look at the extremes... if 100% of the kWh generated during the day are valued at TOU-EV-1 rates, what would your monthly aggregated bill look like? How about if 100% of the kWh are valued at TOU-D-A rates? For the sake of simplicity, I would leave TOU-D-T out of it for now, since it is much more complicated to calculate. With proportioning, your real aggregated bill should be between those extremes.

Once you have the bounded estimate of your aggregated bill, you can compare that to what your bill would be if you scrapped the EV meter and just ran under a single TOU account. With any luck, the billing under the single meter will not land in the bounded range, so the choice will be clear.

Keep in mind that aggregation costs $5 / mo, with a $25 setup charge per account. That is a decent headwind to overcome.

Do you have a 15 min (or hourly) breakdown or projection of your usage under the two meter plan?

[gvl]

My reading of your quote (and IANAL) is that any surplus generated by A1 at any time period during the billing cycle will be allocated between A1 and A2 based on the import billing associated with that meter. And both the export and import numbers are the value of the real time import and export counters in the meters, not the net value at the end of the billing period.

If both A1 and A2 import 50kW and A1 produces an export (not NET export) of 40kW, then 20kW of export is credited to A1 and 20 to A2.
If A1 does not have any import at all, then all of the export credit will go to A2.
If A1 has a net import of 10k on its own, then it will not be as simple as allocating the entire export to A1 only.

It certainly will make a difference if you have a net surplus over the two accounts or if you have TOU or EV rates in the picture for the two metered services.

With real time import counter the quote makes more sense, in particular the statement about the 15-minute interval metering for all accounts and not only on the one that exports.

In my case A2 is on the EV-TOU rate, if I'm interpreting the quote correctly the credits for the energy allocated to it will be calculated using this EV-TOU rate. If so aggregating doesn't sound like a very good deal in this scenario as EV-TOU rates are lower than domestic TOU when the sun is up and EV charging is mostly done at super-off-peak at night, and I will be better of just with a single meter. Sounds like aggregation works best for accounts that are on the same rate schedule. I wish SCE could explain it in layman terms to their customers, it almost feels like they are purposely not helpful.

[gvl]

...
Keep in mind allocation is done on 15 minute intervals. At night, all of your accounts are net consumers, so all usage is valued at whatever the TOU rate is for that time period.

During the day, if you don't aggregate, let's say you are on TOU-D-A. If you generate 1 kWh over a 15 min period on-peak in summer, that would be credit worth $0.46. If you do aggregate, that 1 kWh will be proportionally split between the accounts. So, 0.5 kWh would be worth credit under the TOU-EV-1 plan, ($0.36267 * 0.5), and the remaining would be a credit for the original plan, or ($0.46 * 0.5).

Based on my experience on trying to figure out the proportioning scheme for TOU-D-T, It won't make sense without looking at an actual bill. The example provided in the link above doesn't provide enough detail to be sure I understand.

You could probably make the decision without fully understanding the proportioning. Just look at the extremes... if 100% the kWh generated during the day are valued at TOU-EV-1 rates, what would your monthly aggregated bill look like? How about if 100% of the kWh are valued at TOU-D-A rates? For the sake of simplicity, I would leave TOU-D-T out of it for now, since it is much more complicated to calculated. With proportioning, your real aggregated bill should be between those extremes.

Once you have the bounded estimate of your aggregated bill, you can compare that to what your bill would be if you scrapped the EV meter and just ran under a single TOU account. With any luck, the billing under the single meter will not land in the bounded range, so the choice will be clear.

Keep in mind that aggregation costs $5 / mo, with a $25 setup charge per account. That is a decent headwind to overcome.

Do you have a 15 min (or hourly) breakdown or projection of your usage under the two meter plan?

Can you think of a situation when getting credits on the TOU-EV-1 plan can be beneficial? 95% of all charging is done at night on the super-off-peak rate. Sounds like it is a lose-lose situation to aggregate in the TOU-D-A case, just need some conduit work to hook up my charger to the main panel.

[sensij]

Nope. Especially since the cost to charge at night under TOU-D-A is $0.11/kWh, pretty much the same as TOU-EV-1... I see no benefit to aggregation if the base rate is TOU-D-A.

I guess if your net meter was on a standard TOU-D tier plan, it is possible that the TOU-EV-1 credits would be worth more than the base credits. I'm not sure that would result in a better outcome than TOU-D-A, but I suppose it would be possible if you have heavy on-peak usage after the sun goes down.

[gvl]

Thanks, this matches my assessment, wanted to make sure I wasn't misinterpreting how they calculate. To make things more confusing I earlier spoke with someone from the EV department at SCE and was told that credits are always calculated using the meter with solar, he (or anyone else at SCE I spoke with regarding aggregation for that matter) didn't sound all that familiar with aggregation so I just assumed he was wrong.

Now, if I can't get on TOU-D-A for whatever reason and end up with TOU-D-T I probably will need to sit down and see if aggregation with TOU-EV-1 makes more sense. For the time being I'm keeping my EV meter with TOU-EV-1 separately, want to get solar is up and running first.

[gvl]

I guess if your net meter was on a standard TOU-D tier plan, it is possible that the TOU-EV-1 credits would be worth more than the base credits. I'm not sure that would result in a better outcome than TOU-D-A, but I suppose it would be possible if you have heavy on-peak usage after the sun goes down.

Good idea, I guess I'll have to see how TOU works out for my needs, it is possible that TOU-D with aggregation can produce similar results with less stress.

EDIT: I meant residential tiered plan (Rate Schedule D), not TOU-D-T, but same idea.

[silversaver]

TOU-EV-1 plan uses 2 meter (home and EV) were peak from noon to 9pm, rest are off peak. What are you paying per kWk during off peak???

The point is: you CANNOT mix with TOU-D or TOU-D-A.

In other words, you cannot mix and create your own combo. Saving $$$ is one thing, creative is another.

https://www.sce.com/NR/sc3/tm2/pdf/ce360.pdf

https://www.sce.com/NR/sc3/tm2/pdf/ce114-12.pdf

[sensij]

The point is: you CANNOT mix with TOU-D or TOU-D-A.

Incorrect. Read the tariff documents you linked for TOU-EV-1.

APPLICABILITY
Applicable exclusively to the charging of electric vehicles, as defined in Rule 1, on a separate meter provided by SCE in Single Family Dwellings concurrently served under a Domestic schedule.

TOU-EV-1 applies only to the meter which is used for the EV charging. The other meter may have whatever other plan domestic rate plan the customer chooses (schedule D, or TOU-D-#). Think about it... if you couldn't have two accounts, what would be the point of the separate meter?

[silversaver]

Incorrect. Read the documents you linked. TOU-EV-1 applies only to the meter which is used for the EV charging. The other meter may have whatever other plan the customer chooses. Think about it... if you couldn't have two accounts, what would be the point of the separate meter?

read the 1st paragraph or 1st link.

start from jan 2015, TOU-D (3 kind of TOUs: TOU-D-A, TOU-D-B AND TOU-D-T) is replacing TOU-TEV plan.

https://www.sce.com/wps/portal/home/residential/rates/residential-plan/!ut/p/b1/hc_RCoIwFAbgZ-kB8hxdtXU5YekssjTSdhMWtgR1YZGv34JuIqr_7ofvwPlBQQ6qLe6VLm6VaYv62dVk77KAhzJFyXwiUPoYL3nCcU7Rgp0F-CUc_91noN5JsBqPUEZ0g5SmLpvRD5BQz4KtWMS-6yHzXmAaoAij2ILNmqAka1ymnBPEyQv8eDICpWtzsIMzASqopEj4cxpvD4RpUF15Kruyc87meoO873tHG6Pr0jmaBi5NjpUcqpkeDB4pM9PK/dl4/d5/L2dBISEvZ0FBIS9nQSEh/

https://www.sce.com/wps/portal/home/residential/rates/residential-rates/!ut/p/b1/rZNNT8MwDIZ_CweOWZymJdkxQ6V0Q_sGtlymJM26Tms7umqDf0867cCHGCDIybYe23ptB0s8w7JQ-yxVdVYWatP48mpBeCRu4wnEvEd9iDt-OB1ce1FvCA6YOwC-eAI-5Hdo6PJh0BdjAT0G-BFLLLdVubamzhI8TyhfqgR8REg7Qb7HAsSNb1HgEaBtDQHoZZNiinpbr_B8Z-zClEVti3phi0s42ZdQ2V2WOCtTG-eo2u7exdAxdGxumr4k8TgF5aGlsYB8ohnSWgWIaCCBocCs9k9iz6j5ZlhHsW-RaBg4pMumwNiE8Bv2CRgzzwEP4d2gQzzg3gloRxDedgcOmI4oxHQE_YkQFODqBJzZSBfLdFNqt93HEMsoi8OxaKSJQlOeYlnZpa1s1VqVuxrPDodDKy3LdGNbpszx3I2AfakxIHjyy5meLzhk_1ww8H9dsPuDP5Ctn56kcGfZnN-zG9sf73Kb3-ec5mgGWYzkzT7PF_0-Upq_HC5eAWL8qLE!/dl4/d5/L2dBISEvZ0FBIS9nQSEh/

[silversaver]

"Important information for current TOU-D-TEV Customers

The new Residential Time-of-Use Plan, TOU-D, was introduced January 1, 2015 to replace our Home & Electric Vehicle Plan, TOU-D-TEV. Current TOU-D-TEV customers will be transitioned to the new rate during March and April 2015. You can decide to remain on this new plan, or switch to another rate plan of your choice."


"Applicable (for TOU-D) as an optional base rate to customers eligible for service under Schedule D and
D-CARE. This Schedule is not applicable to customers receiving service under Schedules D-FERA,
DM, DMS-1, DMS-2, DMS-3, or in combination with DS. Electric vehicle load that is separately
metered under Schedule TOU-EV-1 is ineligible for service under this Schedule. This Schedule is
available subject a cap of 200,000 customer accounts, which may not be exceeded. Service under
this Schedule is subject to meter availability.

[silversaver]

Incorrect. Read the tariff documents you linked for TOU-EV-1.



TOU-EV-1 applies only to the meter which is used for the EV charging. The other meter may have whatever other plan domestic rate plan the customer chooses (schedule D, or TOU-D-#). Think about it... if you couldn't have two accounts, what would be the point of the separate meter?

The old TOU-EV-1 can combine with schedule D or old TOU without super low off peak rate, but not anymore!!

[gvl]

"Important information for current TOU-D-TEV Customers

The new Residential Time-of-Use Plan, TOU-D, was introduced January 1, 2015 to replace our Home & Electric Vehicle Plan, TOU-D-TEV. Current TOU-D-TEV customers will be transitioned to the new rate during March and April 2015. You can decide to remain on this new plan, or switch to another rate plan of your choice."


"Applicable (for TOU-D) as an optional base rate to customers eligible for service under Schedule D and
D-CARE. This Schedule is not applicable to customers receiving service under Schedules D-FERA,
DM, DMS-1, DMS-2, DMS-3, or in combination with DS. Electric vehicle load that is separately
metered under Schedule TOU-EV-1 is ineligible for service under this Schedule. This Schedule is
available subject a cap of 200,000 customer accounts, which may not be exceeded. Service under
this Schedule is subject to meter availability.

Are you quoting from this pdf document?

All it is saying is that a dedicated EV meter that is on the TOU-EV-1 schedule cannot be put on TOU-D, it says nothing about combining the TOU-D schedule household meter with the TOU-EV-1 schedule EV meter, at least this is how I read it.

I wonder how close they are to the 200 cap, and why it is there.

[silversaver]

Are you quoting from this pdf document?

All it is saying is that a dedicated EV meter that is on the TOU-EV-1 schedule cannot be put on TOU-D, it says nothing about combining the TOU-D schedule household meter with the TOU-EV-1 schedule EV meter, at least this is how I read it.

I wonder how close they are to the 200 cap, and why it is there.

TOU-D uses only 1 meter. If both schedules cannot be combine, what make you think you can combining both meters? The TOU-D-A offering 11 cents / kWh during 10pm to 8am. why would you need a 2nd meter for just EV? trying to get 9 cents/10 cents for your EV?

I think you are way too smart. I'm out