Optimizing NEM2.0 for PG&E EV2-A rate

[YRide]

Does anyone have experience in ensuring things are optimized for maximum monetary offset? I’m PGE & EV2A rate.

My understanding is that PGE has a cap to how much excess generation you can send to the grid each month, based more or less on the PVWatts calculations once all your system parameters are passed in.

Is this the the theoretical maximum in a “net” (usage - generation) calculation? Meaning you could almost never hit this threshold assuming you live in the house and consume electricity? Or is this a generation only limit?

I thought I remember seeing somewhere that you need to be careful about not generating off-peak onto grid, because PGE would count those kWh’s first, and then prevent you from getting high $ credit for peak generation kWh’s.

Also, I plan to use 4x powerwalls to TOU shift my generation. On most days (in the summer at least) I should be able to fully charge the powerwalls during the day as well as manage small home loads. Is Time Based Control smart enough to wait through the shoulder period and not generate to grid until it’s actual peak (not partial peak) to fully maximize cost benefits? Or do i need to manually adjust the rate plan amounts to force it into more ideal behavior?

 

[getakey]

I thought I remember seeing somewhere that you need to be careful about not generating off-peak onto grid, because PGE would count those kWh’s first, and then prevent you from getting high $ credit for peak generation kWh’s.

Not true. PG&E will credit everything you send to grid. Your solar should charge the PWs first, then power house with any excess to grid. Then use PWs to get through Peak. Only gotcha is if you get into negative NEM at true-up. You won't get that back. That said, I think it will be difficult to get to negative NEM on EV2-A unless your system is way oversized

 

[YRide]

Not true. PG&E will credit everything you send to grid. Your solar should charge the PWs first, then power house with any excess to grid. Then use PWs to get through Peak. Only gotcha is if you get into negative NEM at true-up. You won't get that back. That said, I think it will be difficult to get to negative NEM on EV2-A unless your system is way oversized

Isn’t there both a an annual limit (not really limit, but if you go negative on annual true uo you go from retail to wholesale rate…so effectively zero) as well as a monthly generation limit? Isn’t the latter on that “black & white” bill insaw someone mention.

@swedge didnt you comment on this stuff recently in another thread?

 

[getakey]

Isn’t there both a an annual limit (not really limit, but if you go negative on annual true uo you go from retail to wholesale rate…so effectively zero) as well as a monthly generation limit? Isn’t the latter on that “black & white” bill insaw someone mention.

@swedge didnt you comment on this stuff recently in another thread?

You can be negative NEM and not a net Producer. I did that one year. I'm always a net user, but I aggressively used the PWs (set low reserve) and ended up negative NEM at true-up. I had added PWs to existing solar, so I didn't know what to expect. Now I can manage them (using higher reserve) to get a zero NEM. I adjust my reserve depending on time of year and weather forecast. We've had storms that did not trigger storm watch that caused an outage. That said, I'm still on EV1-A so as soon as I shift to EV2-A will have to relearn what works
You do only get paid at wholesale if you are a net producer.

 

[h2ofun]

Not true. PG&E will credit everything you send to grid. Your solar should charge the PWs first, then power house with any excess to grid. Then use PWs to get through Peak. Only gotcha is if you get into negative NEM at true-up. You won't get that back. That said, I think it will be difficult to get to negative NEM on EV2-A unless your system is way oversized

Nope, I am WAY oversized, and I only can get max of what they calculated. One month I lost 1MKwh worth!

I was WAY negative on True up. Got like whole sale credit. At least with my EV, going to give them less.

 

[swedge]

Isn’t there both a an annual limit (not really limit, but if you go negative on annual true uo you go from retail to wholesale rate…so effectively zero) as well as a monthly generation limit? Isn’t the latter on that “black & white” bill insaw someone mention.

@swedge didnt you comment on this stuff recently in another thread?

I did, in a discussion about using the PW options to optimize returns : New Powerwall Advanced Options [Toggles for charging from and discharging to grid from powerwalls]

Under PG&E NEM1 and 2, each month you are limited to credit on export of only as many kWh as the estimate your solar could produce. Each year if your NEM credit is greater than your cost (i.e. PG&E would owe you money), the NEM credit is zeroed out, i.e. not paid. If your total kWh export is greater than your total import, you are credited at a wholesale rate which in far below the retail NEM credit.

I am not up on the NEM3 rules because I hope the legislature or courts will kill "NEM3" (which is not really NEM at all) before my NEM2 grandfathering expires.

 

[YRide]

I did, in a discussion about using the PW options to optimize returns : New Powerwall Advanced Options [Toggles for charging from and discharging to grid from powerwalls]

Under PG&E NEM1 and 2, each month you are limited to credit on export of only as many kWh as the estimate your solar could produce. Each year if your NEM credit is greater than your cost (i.e. PG&E would owe you money), the NEM credit is zeroed out, i.e. not paid. If your total kWh export is greater than your total import, you are credited at a wholesale rate which in far below the retail NEM credit.

I am not up on the NEM3 rules because I hope the legislature or courts will kill "NEM3" (which is not really NEM at all) before my NEM2 grandfathering expires.

Thx!

Drilling into the monthly caps…is that a net export limit? Or is it a directional export limit?

Say I charged up my 54kW (let’s say from zero) of powerwalls during the off peak day (using a combo or all Solar, let’s call it 30kWh, until 3p + 24kWh grid to make up remainder)…then at 4p (EV2A peak) I switch to dumping all solar (let’s say it’s 4kW @ 4p, 3kW @ 5p, 2kW @ 6p, 1kW @ 7p (10kWh during peak) + all powerwalls down to 5% reserve (so 51.3kWh)….

Does this mean for that day (used to calculate monthly limit) I’m generating 61.3kWh? Or am I generating only 61.3 - 24 = 37.3kWh for the day?

 

[power.saver]

Does this mean for that day (used to calculate monthly limit) I’m generating 61.3kWh?

Yes, 61.3kWh is that day's generation for the monthly limit calculation.

 

[YRide]

Yes, 61.3kWh is that day's generation for the monthly limit calculation.

Ok, thx. So the daily (or monthly) powerwall-based arbitrage you can run is limited by the theoretical output of your solar system?

 

[power.saver]

Ok, thx. So the daily (or monthly) powerwall-based arbitrage you can run is limited by the theoretical output of your solar system?

Correct. If you charge from grid and discharge in peak, plus export all solar, you risk going over your monthly limit.

If you only charge from solar, and export in peak or whenever, you won't go over the limit because you didn't do any grid arbitrage.

 

[swedge]

Thx!

Drilling into the monthly caps…is that a net export limit? Or is it a directional export limit?

Say I charged up my 54kW (let’s say from zero) of powerwalls during the off peak day (using a combo or all Solar, let’s call it 30kWh, until 3p + 24kWh grid to make up remainder)…then at 4p (EV2A peak) I switch to dumping all solar (let’s say it’s 4kW @ 4p, 3kW @ 5p, 2kW @ 6p, 1kW @ 7p (10kWh during peak) + all powerwalls down to 5% reserve (so 51.3kWh)….

Does this mean for that day (used to calculate monthly limit) I’m generating 61.3kWh? Or am I generating only 61.3 - 24 = 37.3kWh for the day?

Directional. It is the monthly total of your exports, compared with the estimated solar production for the same month. (And the estimate appears to be based on your billing month, not the calendar month.)

The estimate uses NERL's PVWatts, based on your solar panels, orientation, inverter specs, etc. I'm not sure if typical cloud cover is included, but actual weather is not. So, if you consume any power during daylight, and don't grid charge, you will not reach the limit. Situations where one exceeds the limit might include having more solar that was included in the interconnection application given to PG&E, or perhaps grid charging.

The calculation does not depend on TOU rates, as it is simply based on total kWh exported. If one does exceed the limit, I do not recall exactly how the kWh disallowed are allocated to the TOU rate periods, perhaps prorated by export fraction in each period.

I don't understand your exact scenario. Perhaps there is a typo at "combo or all Solar"? Perhaps you meant "combo of"? If so, your solar produced 40 kWh, 30 kWh of which went into PW, and 10 of which was exported directly. That 10 kWh of direct solar, plus 51.3 of PW discharge totaling 61.3 kWh was exported. If the PVWatts estimate matched your actual production, you'd have exported 21.3 kWh more than your estimated production. So you'd be over the limit. But you didn't mention any consumption at all, which would have reduced the overage. In real life, during the solar production and peak period, your consumption will reduce your direct export and the amount your PW can export during peak, so it typically won't be that much extra. But with 4 PW's it is certainly possible to grid charge and export too much. Using a higher backup reserve setting can prevent that.

With my one PW set at 20% reserve, around 30 kWh per day of solar production these days, and 15 kWh of consumption, about half of which is during solar and peak hours, our daily export seldom or never exceed our production, though I do check the detailed bill monthly to be sure.

I think I mentioned elsewhere that I sometimes charge my car after my PW has fully charged till the rate rises so as to reduce the NBC's which would otherwise accuse on power exported during off peak and then re-imported during post midnight charging. This is a nickel and dime savings, often not worth the effort, but it would be worth more if it reduced my export to below the estimated production!

 

[YRide]

Directional. It is the monthly total of your exports, compared with the estimated solar production for the same month. (And the estimate appears to be based on your billing month, not the calendar month.)

The estimate uses NERL's PVWatts, based on your solar panels, orientation, inverter specs, etc. I'm not sure if typical cloud cover is included, but actual weather is not. So, if you consume any power during daylight, and don't grid charge, you will not reach the limit. Situations where one exceeds the limit might include having more solar that was included in the interconnection application given to PG&E, or perhaps grid charging.

The calculation does not depend on TOU rates, as it is simply based on total kWh exported. If one does exceed the limit, I do not recall exactly how the kWh disallowed are allocated to the TOU rate periods, perhaps prorated by export fraction in each period.

I don't understand your exact scenario. Perhaps there is a typo at "combo or all Solar"? Perhaps you meant "combo of"? If so, your solar produced 40 kWh, 30 kWh of which went into PW, and 10 of which was exported directly. That 10 kWh of direct solar, plus 51.3 of PW discharge totaling 61.3 kWh was exported. If the PVWatts estimate matched your actual production, you'd have exported 21.3 kWh more than your estimated production. So you'd be over the limit. But you didn't mention any consumption at all, which would have reduced the overage. In real life, during the solar production and peak period, your consumption will reduce your direct export and the amount your PW can export during peak, so it typically won't be that much extra. But with 4 PW's it is certainly possible to grid charge and export too much. Using a higher backup reserve setting can prevent that.

With my one PW set at 20% reserve, around 30 kWh per day of solar production these days, and 15 kWh of consumption, about half of which is during solar and peak hours, our daily export seldom or never exceed our production, though I do check the detailed bill monthly to be sure.

I think I mentioned elsewhere that I sometimes charge my car after my PW has fully charged till the rate rises so as to reduce the NBC's which would otherwise accuse on power exported during off peak and then re-imported during post midnight charging. This is a nickel and dime savings, often not worth the effort, but it would be worth more if it reduced my export to below the estimated production!

This helps my understanding.

I thought I read somewhere else, though can’t find it now, PGE actually subtracts the off peak kWh’s first, so that you need to watch out for generation then if you are going to hit the limit.

Anyways, based on above, it would seem I should try to get it so PW’s discharge everything during peak (minus my peak consumption…which I should provide with PW’s)…I never charge my EV’s during peak (only off peak, directly from grid)…and in the off chance my solar production during the day fills up my Powerwalls, I should have my EV’s take the excess generation until 4p peak rate rolls around…at which case I should stop charging EV’s, discharge all PW down to reserve + nightly anticipated usage…and then at midnight (or more likely early next morning) finish topping off EV’s from the grid (not PW) with off peak rate.

Is that basically what you said above?

 

[h2ofun]

Thx!

Drilling into the monthly caps…is that a net export limit? Or is it a directional export limit?

Say I charged up my 54kW (let’s say from zero) of powerwalls during the off peak day (using a combo or all Solar, let’s call it 30kWh, until 3p + 24kWh grid to make up remainder)…then at 4p (EV2A peak) I switch to dumping all solar (let’s say it’s 4kW @ 4p, 3kW @ 5p, 2kW @ 6p, 1kW @ 7p (10kWh during peak) + all powerwalls down to 5% reserve (so 51.3kWh)….

Does this mean for that day (used to calculate monthly limit) I’m generating 61.3kWh? Or am I generating only 61.3 - 24 = 37.3kWh for the day?

export only, not what you used

 

[wwu123]

Just curious then, in case I ever add ESS and am able to grid-arbitrage - if it is based on PVWatts estimate of your reported solar system specs, is the monthly limit seasonal, i.e. the monthly limit in winter is much lower than in summer, because that's the expected production of the solar panels? Or is the monthly limit the total annual PVWatts estimate, divided evenly by 12 months, to set a consistent monthly limit?

 

[h2ofun]

Just curious then, in case I ever add ESS and am able to grid-arbitrage - if it is based on PVWatts estimate of your reported solar system specs, is the monthly limit seasonal, i.e. the monthly limit in winter is much lower than in summer, because that's the expected production of the solar panels? Or is the monthly limit the total annual PVWatts estimate, divided evenly by 12 months, to set a consistent monthly limit?

Its the monthly PW watts, per month. No averages, or anything, just per month. With my batteries, I never get close to the PGE number, even in the winter.

 

[swedge]

This helps my understanding.

I thought I read somewhere else, though can’t find it now, PGE actually subtracts the off peak kWh’s first, so that you need to watch out for generation then if you are going to hit the limit.

Anyways, based on above, it would seem I should try to get it so PW’s discharge everything during peak (minus my peak consumption…which I should provide with PW’s)…I never charge my EV’s during peak (only off peak, directly from grid)…and in the off chance my solar production during the day fills up my Powerwalls, I should have my EV’s take the excess generation until 4p peak rate rolls around…at which case I should stop charging EV’s, discharge all PW down to reserve + nightly anticipated usage…and then at midnight (or more likely early next morning) finish topping off EV’s from the grid (not PW) with off peak rate.

Is that basically what you said above?

A caveat: we are talking about NEM1 and 2 in N. Calif with out a community aggregation plan. In other circumstances, your milage will vary!

Yes, basically right. In fact, this is how PW behaves with Grid Charging and Export Everything settings. It estimates how much to save for your evening consumption, and even appears to watch the weather forecast so it can grid charge before sun-up if it thinks it'll be too cloudy to get to 100% before 3pm when the rate climbs.

A couple fine points. Regarding your after midnight car charging, you may want to set the charge limit a bit lower to leave room for that excess solar tomorrow after the PW's are full. Again, this direct solar to car charging saves pennies on NBCs and may help offset any grid charging you do. Oh, and Tesla has said that an upcoming version of the Tesla App will automate direct solar car charging. That will be nice - if it actually does what we want.

Second point is that with 4 PW's it won't be hard to export more than the PG&E estimate. To avoid this, check your monthly detailed bill. Here is mine for this month's bill, page 3 of the "black and white" detailed bill:

They estimated my solar generation as 867, while my export was only 477 kWh. Thus the entire 477 is eligible for credit and I have no problem with exporting too much. But your 4 PW's could grid charge and export double your solar production, so you should probably keep an eye on it. Both the estimate and (of course) your solar production and export will vary every month, so it may take some effort to find a backup reserve setting which works best for you.

Also bear in mind that if you accumulate more NEM credit over the year than you owe, at your true-up PG&E just swallows the excess credit and does not even say thank you. So you may not need to max out your export and can save some wear and tear by not cycling your PW's so deeply.

 

[h2ofun]

A caveat: we are talking about NEM1 and 2 in N. Calif with out a community aggregation plan. In other circumstances, your milage will vary!

Yes, basically right. In fact, this is how PW behaves with Grid Charging and Export Everything settings. It estimates how much to save for your evening consumption, and even appears to watch the weather forecast so it can grid charge before sun-up if it thinks it'll be too cloudy to get to 100% before 3pm when the rate climbs.

A couple fine points. Regarding your after midnight car charging, you may want to set the charge limit a bit lower to leave room for that excess solar tomorrow after the PW's are full. Again, this direct solar to car charging saves pennies on NBCs and may help offset any grid charging you do. Oh, and Tesla has said that an upcoming version of the Tesla App will automate direct solar car charging. That will be nice - if it actually does what we want.

Second point is that with 4 PW's it won't be hard to export more than the PG&E estimate. To avoid this, check your monthly detailed bill. Here is mine for this month's bill, page 3 of the "black and white" detailed bill:

View attachment 939839

They estimated my solar generation as 867, while my export was only 477 kWh. Thus the entire 477 is eligible for credit and I have no problem with exporting too much. But your 4 PW's could grid charge and export double your solar production, so you should probably keep an eye on it. Both the estimate and (of course) your solar production and export will vary every month, so it may take some effort to find a backup reserve setting which works best for you.

Also bear in mind that if you accumulate more NEM credit over the year than you owe, at your true-up PG&E just swallows the excess credit and does not even say thank you. So you may not need to max out your export and can save some wear and tear by not cycling your PW's so deeply.

I do not export anything from my PW's. And on top of that, only 1 set even have the option. Never could get tesla to tell me why both sets did not have the same settings

 

[YRide]

A caveat: we are talking about NEM1 and 2 in N. Calif with out a community aggregation plan. In other circumstances, your milage will vary!

Yes, basically right. In fact, this is how PW behaves with Grid Charging and Export Everything settings. It estimates how much to save for your evening consumption, and even appears to watch the weather forecast so it can grid charge before sun-up if it thinks it'll be too cloudy to get to 100% before 3pm when the rate climbs.

A couple fine points. Regarding your after midnight car charging, you may want to set the charge limit a bit lower to leave room for that excess solar tomorrow after the PW's are full. Again, this direct solar to car charging saves pennies on NBCs and may help offset any grid charging you do. Oh, and Tesla has said that an upcoming version of the Tesla App will automate direct solar car charging. That will be nice - if it actually does what we want.

Second point is that with 4 PW's it won't be hard to export more than the PG&E estimate. To avoid this, check your monthly detailed bill. Here is mine for this month's bill, page 3 of the "black and white" detailed bill:

View attachment 939839

They estimated my solar generation as 867, while my export was only 477 kWh. Thus the entire 477 is eligible for credit and I have no problem with exporting too much. But your 4 PW's could grid charge and export double your solar production, so you should probably keep an eye on it. Both the estimate and (of course) your solar production and export will vary every month, so it may take some effort to find a backup reserve setting which works best for you.

Also bear in mind that if you accumulate more NEM credit over the year than you owe, at your true-up PG&E just swallows the excess credit and does not even say thank you. So you may not need to max out your export and can save some wear and tear by not cycling your PW's so deeply.

Very helpful, thank you.

I am on CCA (SVCE). Does this substantially change the math on things? Should I change to PGE to simplify things? I’m going to be offsetting most of my consumption, so I can sleep well at night (for the good of humanity). My understanding is the CCA v PGE production isn’t night a day anyways, wrt clean production.

I’ll be watching this stuff closely once I get PTO and can flip the two toggles “on”.

Looks like I should be ok to have headroom to add that split AC in ADU & electric dryer. Maybe next is swap gas heating for heat pump, that’s really the major one I suppose.

Btw, wrt VPP, that’s just a payment from Tesla direct, right? That doesn’t factor into all the NEM calculations does it?

 

[swedge]

Very helpful, thank you.

I am on CCA (SVCE). Does this substantially change the math on things?

Oh, sorry, I know nothing about SVCE. So I can not comment on their math. Sorry.

Btw, wrt VPP, that’s just a payment from Tesla direct, right? That doesn’t factor into all the NEM calculations does it?

Right. I got a $140 (if memory serves me, which it often does not) check from Tesla, for $2 per kWh exported over 10 or so VPP events last year. The check came with no explanation, so I had to find online where someone had logged the VPP event periods, and back in the Tesla app to get my export data for those periods. The check came a couple months into this year, so it is slow. But PG&E also gave me NEM credits for those kWh, so it was pretty sweet. PG&E had announced that rolling blackouts were likely on those days, but with the help of 5,000 or so of us Tesla VPP, the blackout were not necessary. A big win/win/win for other customers, PG&E, and us PW owners.

 

[cwied]

The calculation does not depend on TOU rates, as it is simply based on total kWh exported. If one does exceed the limit, I do not recall exactly how the kWh disallowed are allocated to the TOU rate periods, perhaps prorated by export fraction in each period.

PG&E takes the most advantageous (for them) interpretation: they remove the excess export credits from highest rate period first. I ran into this once when PG&E double-billed me by accident.