NEM-PS Annual True-Up Calculation [PG&E example]

[wwu123]

That chart is not quite correct.

• NEM1.0 had no NBCs,
• NEM2's credits were at import rates minus NBCs,
• NEM2 NBCs are charged on all imports, not net energy consumed.

I would not trust the "interval" info either. I think the smart meters simply continuously accumulate imports and exports, and report the hourly totals.

A slightly off topic observation: Some of the billing reports the monthly kWh with three decimal places of precision, meaning down to the individual Watt-hour. I don't know where the rounding happens in the billing process, but they show only whole kWh and cents, with no rounding errors totals due to rounding.

While I'm not saying the page or chart is accurate or up-to-date, I think the "errors" you pointed out above are just the discrepancy in how they're explaining NBC's. NBC's are just part of the retail rate, so essentially the retail rate = energy rate + NBC's. Basically they're saying on any interval that is net import, you're paying energy rate + NBC's.

On NEM 1, there's only one interval for the whole year, if you were net import, you paid retail rate = energy rate + NBC's on all the imported kwh.

On NEM 2, if an interval (whether it was 15 min or 60 min or whatever) was net import, you paid retail rate = energy rate + NBC''s. If an interval was net export, you were "credited" retail rate = energy rate + NBC's, and charged NBC's separately. Hence their terms for "basis of credits" and "basis of NBC's calculation".

Not saying their explanation was clear nor consistent, just I think that's what they were trying to say....

 

[swedge]

Very weirdly…since this post, my Powerwall has stopped GC to 99-100% SoC each night…and instead only goes up to 83-86% SoC for the last few days.

So Tesla Energy R&D team that is watching this thread… hi , thank you, and if you could tune it a bit more to get my to only 75% via grid charging each morning that would be ideal. PV should be able to top it off during the day.

I have a hunch about this type of Grid Charging behavior. Mine did not do any trig charging till after I set up Charge on Solar. I suspect that PowerWall sees car charging as part of the consumption which it tries to have enough charging to handle. So, when we consistently charge a car, PW does more grid charging.

I was car charging before CoS became available, but my Tesla Wall Connector was connected between the PG&E meter and the gateway where the grid CT sensors are located. So the PW was unaware of the car charging. When CoS was finally available (correct versions of car, PW and app software) it worked poorly. So I moved the CT to the feed from the meter and the PW could now include the car charging in it's, uh..., thinking. At it started grid charging when it really didn't need to.

I don't think we have a good understanding of what PW learns about our usage and solar production, but it does take a few days before it gets good at discharging to the grid during peak periods for EE without going below the backup reserve. Car charging, which tends to be very large and often variable from day to day, may throw PW a wrinkle.

YRide, you might want to compare your car charging with the PW grid charging on the following day, to see if there is maybe some interaction.

One other observation: It appears that PW also pays attention to weather forecasts. After a few sunny days with no grid charging, it will sometimes grid charge at night on days when the forecast calls for overcast. This is difficult to verify experimentally, what with weather being outside of our control.

I am seriously considering moving my grid CT's back to the gateway and working out a way to automate car charging on solar in excess of what is needed to fully charge the PW. But that sounds like work, and this time of year I don't have much extra solar anyway.

 

[swedge]

Do you have the link for the approved NEM2 document?

PDF: https://www.pge.com/tariffs/assets/pdf/tariffbook/ELEC_SCHEDS_NEM2.pdf

 

[swedge]

Yep, was able to click through all three...one is clearly my residential gas, one is unknown and one is an eletric rate "H2EV2AN". I noted that none of the two non-gas ones show NEM2PS, so i'm thinking stuff just hasnt processed rate. Both the non-gas service ID's have dates the day before my PTO.

@Redhill_qik does is 11/1/20 the date of your PTO?

Since my PTO was late June, i'm just assuming it's still in the transfer phase. Didnt most people indicated this can take 2-3, or sometimes 4 (with all the NEM2 push) months?

YRide,

I finally went back to see how long it took from my last PTO till the B&Ws showed up.

The PTO for some additional solar panels was effective 6/28/22. The electric section was completely absent from my blue bills starting in August which should have been the first bill to include the new solar. Finally, the blue bill dated 12/5/2022 included electrical charges for periods ending in July, Aug, Sept, Oct and November. I think I received all those B&W bills sometime after that, though they were probably downloadable once the December blue bill was done.

There was some confusion in my case which might have caused some delay. The 6/28 PTO was rescinded and then reissued with an effective date of 8/30, but all the B&W bills appear consistent with the 6/28 start date. Also, this PTO changed me from NEM1 to NEM2, sigh, another wrinkle. The new Blue bills all show my electric Rate Schedule as "NEM2PS M", the PS of which I believe refers to paired storage.

Anyway, if yours goes with the same speed mine did, you may still have a while to wait for the joy of B&W bills.

PG&E has changed their web site a bit, and the access to the B&W detailed bills has moved slightly, but it is still there. The new location of "Hi, YourName: Account" is on the left side, and the account number has a drop-down which includes the link for "My Accounts and Services".

 

[Redhill_qik]

Imported power in kWh is there by billing period, but not by calendar month, nor by 5/15min interval (didn’t even know they did that for NBC).

I’m trying to think if NBC’s change with tariff changes? I think they do, it actually looks like NBC’s went down from 3.541¢/kWh to 3.271¢/kWh in Sep tariff change…does that align with your understanding?

In your billing for 9/8 through 10/9 the NBCs are almost exactly the same as they should be if the NBC interval was hourly with the rate of $0.03273. There is a small discrepancy of $0.01 between the two periods, but that is probably a weird PG&E rounding issue.

Period	kWh	NBC Cost	NBC Billed
1 Peak	-798.0240​
1 Part	-70.7520​
1 Off	1864.1110​
1 Net	995.3350​	$32.57731​	$32.59​
2 Peak	-256.1970​
2 Part	6.3500​
2 Off	756.0200​
2 Net	506.1730​	$16.56704​	$16.56​
Net Total	1501.5080​	$49.14436​	$49.15​

You are running your system in different way than I am, but for a rough similar period my B&W bill absolute import amount was 23 kWh higher than my hourly import numbers. It is possible that either your minimum meter interval is only an hour or maybe due to your Powerwall charge/discharge cycling settings there was no difference for you.

The NBC rate of $0.03273 has not changed since 7/1/23. It appears that you back calculated the NBC rate for your prior bill as $0.03541 versus the correct rate of $0.03273. This indicates that during the prior period your absolute imports were higher than the reported hourly imports on the bill.

 

[holeydonut]

In your billing for 9/8 through 10/9 the NBCs are almost exactly the same as they should be if the NBC interval was hourly with the rate of $0.03273. There is a small discrepancy of $0.01 between the two periods, but that is probably a weird PG&E rounding issue.

Period	kWh	NBC Cost	NBC Billed
1 Peak	-798.0240​
1 Part	-70.7520​
1 Off	1864.1110​
1 Net	995.3350​	$32.57731​	$32.59​
2 Peak	-256.1970​
2 Part	6.3500​
2 Off	756.0200​
2 Net	506.1730​	$16.56704​	$16.56​
Net Total	1501.5080​	$49.14436​	$49.15​

You are running your system in different way than I am, but for a rough similar period my B&W bill absolute import amount was 23 kWh higher than my hourly import numbers. It is possible that either your minimum meter interval is only an hour or maybe due to your Powerwall charge/discharge cycling settings there was no difference for you.

The NBC rate of $0.03273 has not changed since 7/1/23. It appears that you back calculated the NBC rate for your prior bill as $0.03541 versus the correct rate of $0.03273. This indicates that during the prior period your absolute imports were higher than the reported hourly imports on the bill.

You’ll appreciate that the PG&E automated billing emails are now include a true up estimate. I guess this is to avoid shocking customers with big true ups?

They still refuse to actually explain the NBC rate and gross calculation in a way for normal plebes to understand (who don’t have a pHD or PHD in energy policy or bill-reading). They make it clear the MDC reduces the owed NBC balance, but they don’t explain the NBC very well.

 

[YRide]

You’ll appreciate that the PG&E automated billing emails are now include a true up estimate. I guess this is to avoid shocking customers with big true ups?

They still refuse to actually explain the NBC rate and gross calculation in a way for normal plebes to understand (who don’t have a pHD or PHD in energy policy or bill-reading). They make it clear the MDC reduces the owed NBC balance, but they don’t explain the NBC very well.

View attachment 1000556

It feels like true-up “estimate” is a bit misleading though. It’s more like a cumulative sum of your true up cost through the date of the bill. So as you note, it will gradually make people more and more aware of their true up over the course of the year, and the closer you get to true up date the more accurate it will be…but early on in the year…it will not really be an estimate, there’s nothing really predictive about it (maybe after your first year of true up it might take into account previous years to simulate a full year at any given point…but I doubt it).

But overall, it should give people a little more perspective and hopefully a little less shock.

 

[holeydonut]

It feels like true-up “estimate” is a bit misleading though. It’s more like a cumulative sum of your true up cost through the date of the bill. So as you note, it will gradually make people more and more aware of their true up over the course of the year, and the closer you get to true up date the more accurate it will be…but early on in the year…it will not really be an estimate, there’s nothing really predictive about it (maybe after your first year of true up it might take into account previous years to simulate a full year at any given point…but I doubt it).

But overall, it should give people a little more perspective and hopefully a little less shock.

I loathe to do this, but I’m actually going to defend PG&E on this one. From what I understand, they are applying some basic math to determine if the trajectory of the annual NEM is headed for a deficit.

For example I’m just past halfway on my annual NEM. And the distribution portion (I’m on a CCA for generation) is graphed like this in the latest bill.

If I am to believe what I was told… if a homeowner was near NEM 2 break-even right now, then PG&E would factor in the expected next few months of deficit and apply a forecasted true up.

Unfortunately I don’t personally know anyone with an undersized solar array that is getting this type of bill to compare notes.

 

[Redhill_qik]

If I am to believe what I was told… if a homeowner was near NEM 2 break-even right now, then PG&E would factor in the expected next few months of deficit and apply a forecasted true up.

Unfortunately I don’t personally know anyone with an undersized solar array that is getting this type of bill to compare notes.

I have seen bills from a few folks that are undersized and I haven't seen any forecasting happening, just the cumulative year-to-date amounts. The email that you received from PG&E said "Estimated year-to-date Solar energy Charges to be paid at True-Up" has both "Estimated" and "year-to-date". The amount of $129.57 is higher than what looks like -$544 in energy charges, so my guess is that this equivalent to your current NBCs minus your MDCs.

I think that if PG&E tried to estimate the true-up based on what they know of the solar array and past energy usage they would most likely get it wrong and then have another set of angry customers clogging up their phone lines. They might be trying to do this, but I doubt it as the error bars are likely to be large and it is far simpler to just put the YTD numbers on the bill.

 

[YRide]

I have seen bills from a few folks that are undersized and I haven't seen any forecasting happening, just the cumulative year-to-date amounts. The email that you received from PG&E said "Estimated year-to-date Solar energy Charges to be paid at True-Up" has both "Estimated" and "year-to-date". The amount of $129.57 is higher than what looks like -$544 in energy charges, so my guess is that this equivalent to your current NBCs minus your MDCs.

I think that if PG&E tried to estimate the true-up based on what they know of the solar array and past energy usage they would most likely get it wrong and then have another set of angry customers clogging up their phone lines. They might be trying to do this, but I doubt it as the error bars are likely to be large and it is far simpler to just put the YTD numbers on the bill.

I agree, I don’t believe there is any forecasting. It’s just a running cumulative YTD total it would seem.

If your NEMC > NBC + PCIA - MDC…then it will show your NEMC. Conversely, if your NBC + PCIA - MDC > NEMC, it will show your NBC + PCIA - NEMC (this is the case for me so far).

As notes earlier, each month you get closer to your true-up date you get a progressively more accurate estimate…so this should both give the consumer some early guidance on the trajectory (not accounting for seasonal shifts however) and give them a couple months warning towards the ballpark of the final bill. So theoretically true-up should be a shocking surprise for the “lay person”. I believe that is valuable to the wide range of customers for a topic we’ve all joked is PhD worthy.

 

[Redhill_qik]

I agree, I don’t believe there is any forecasting. It’s just a running cumulative YTD total it would seem.

View attachment 1002387

View attachment 1002388

If your NEMC > NBC + PCIA - MDC…then it will show your NEMC. Conversely, if your NBC + PCIA - MDC > NEMC, it will show your NBC + PCIA - NEMC (this is the case for me so far).

As notes earlier, each month you get closer to your true-up date you get a progressively more accurate estimate…so this should both give the consumer some early guidance on the trajectory (not accounting for seasonal shifts however) and give them a couple months warning towards the ballpark of the final bill. So theoretically true-up should be a shocking surprise for the “lay person”. I believe that is valuable to the wide range of customers for a topic we’ve all joked is PhD worthy.

Wow $521 in NBCs! That's roughly 16,000 kWh of imports. Pre-solar my usage was less than 9,000 kWh.

 

[YRide]

Wow $521 in NBCs! That's roughly 16,000 kWh of imports. Pre-solar my usage was less than 9,000 kWh.

That’s what 3x EV and 4x PW (with 0% reserve, GC & EE turned on) will do to you.

I’m still trying to dial-in the some of the aspects of PW with custom rates. And based on how my first year of NEM2 goes, I’ll probably increase my reserve to >0% so I can lower the NBC’s next year.

Still haven’t seen the B&W bill, so a little worried I might lose some peak NEM2 credits because I’m not aware of what my monthly export limit is (other then PVWatts approximation via the calculator).

 

[Redhill_qik]

That’s what 3x EV and 4x PW (with 0% reserve, GC & EE turned on) will do to you.

I’m still trying to dial-in the some of the aspects of PW with custom rates. And based on how my first year of NEM2 goes, I’ll probably increase my reserve to >0% so I can lower the NBC’s next year.

Still haven’t seen the B&W bill, so a little worried I might lose some peak NEM2 credits because I’m not aware of what my monthly export limit is (other then PVWatts approximation via the calculator).

Grid Charging so that you can Export Everything during Peak for price arbitrage explains the high imports and your negative delivery charge balance.

 

[YRide]

Grid Charging so that you can Export Everything during Peak for price arbitrage explains the high imports and your negative delivery charge balance.

Correct. I prob didn’t need to GC/EE as much, so can raise the reserve %. Will have added benefit (beyond reducing NBC’s) of wearing the PW’s less, and keeping me a bit more protected for the PW warranty.

I’m still trying to get a feel for how much i will catch up in late spring as I close in on June true-up. Those months should be good for production.

 

[holeydonut]

That’s what 3x EV and 4x PW (with 0% reserve, GC & EE turned on) will do to you.

I’m still trying to dial-in the some of the aspects of PW with custom rates. And based on how my first year of NEM2 goes, I’ll probably increase my reserve to >0% so I can lower the NBC’s next year.

Still haven’t seen the B&W bill, so a little worried I might lose some peak NEM2 credits because I’m not aware of what my monthly export limit is (other then PVWatts approximation via the calculator).

Are you actually able to use all those NEM credits from the rate arbitrage?

I’ll probably have excess this year since we went back to ICE for one of our vehicles.

 

[YRide]

Are you actually able to use all those NEM credits from the rate arbitrage?

I’ll probably have excess this year since we went back to ICE for one of our vehicles.

As far as I can tell, yeah. Running deficit right now, but spring sun will catch up.

We’ll still remain a net importer of power (3x EV, will add 2nd AC, etc), but hopefully close to break even on $ credits. But in the end it will be NBC’s that I think will dominate.

NBC’s are somewhat predictable in this case, so I think I’m gonna wind up like $1,200…avg about $100/mo. I think. Let’s see…

 

[h2ofun]

As far as I can tell, yeah. Running deficit right now, but spring sun will catch up.

We’ll still remain a net importer of power (3x EV, will add 2nd AC, etc), but hopefully close to break even on $ credits. But in the end it will be NBC’s that I think will dominate.

NBC’s are somewhat predictable in this case, so I think I’m gonna wind up like $1,200…avg about $100/mo. I think. Let’s see…

This is going to be interesting for me. Since I have an EV added, and really during the winter, I pull for the grid a lot, so lots of NBC's

During the on season, I really try to charge the EV after the PW's are charged, so I am not charging from the grid and paying NBC"s.
Shall see how it goes. Since I have had such a huge surplus, and only get like 20 cents on the dollar, wasting actually is fine to try and break even.

Now, if Calif starts charging folks more based on income, all the numbers we have all used seemed to be out the door?

 

[holeydonut]

This is going to be interesting for me. Since I have an EV added, and really during the winter, I pull for the grid a lot, so lots of NBC's

During the on season, I really try to charge the EV after the PW's are charged, so I am not charging from the grid and paying NBC"s.
Shall see how it goes. Since I have had such a huge surplus, and only get like 20 cents on the dollar, wasting actually is fine to try and break even.

Now, if Calif starts charging folks more based on income, all the numbers we have all used seemed to be out the door?

Maybe you need to set up a monster Christmas light display to blow through all your NEM.

 

[h2ofun]

Maybe you need to set up a monster Christmas light display to blow through all your NEM.

I did that this year. Just cannot use it all

 

[holeydonut]

I did that this year. Just cannot use it all

Need a pic of this