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

[h2ofun]

h20fun,

When exporting so much do you find that the net surplus compensation greatly exceeds the NBC? It seems like the NBC is always smaller, almost 1/2 the amount of the NSC per kWh.

I ask this because am wondering if it is financially more worthwhile (small though it may be) to charge off peak at night vs charge by solar.

For example if NBC is .04 and NSC is .07 aren't you better off exporting your solar and importing for use, vs using your solar to power home/charge car, when you are over producing in the MWh range? There seems to be some efficiency when I charge my EV with solar too as in solar is producing 5kW car uses 4kW home uses 1 kW, but when I unplug EV home is only using 0,4kW 0.6kW is being used by something when charging by Solar. When I plug the EV back in get the same 5kW from solar, car using 4kW home jumps upto 1kW.

This is assuming that one is way over producing

Never looked, never care, because yep, I generate WAY more than I use. Last year I generated 36 HWh's. Nuts.

I have gotten to the point I do not worry about charging my EV. I just do when easy. I do make sure I do not charge between like 4 to 9 pm at the higher rate.

 

[Redhill_qik]

When charging on solar there is no NBC since you're not importing anything. So it costs you nothing and you gain nothing.

But if you export 1kW solar you get aprox .07 from PGE at true up.
If you charge at night 1kW it costs you .04 for NBC so net if you exported 1kW during day and charged 1kW at night you net gain .03. Is this correct?

Again, this is assuming massive overproduction.

This isn't correct. If you export 1kWh and import 1kW then your net is 0 kWh which means your NSC is $0.00 and you have a NBC of $0.0328.

 

[garrity]

This isn't correct. If you export 1kWh and import 1kW then your net is 0 kWh which means your NSC is $0.00 and you have a NBC of $0.0328.

OK thanks. That makes more sense now, I thought I was missing something.

 

[swedge]

There seems to be some efficiency when I charge my EV with solar too as in solar is producing 5kW car uses 4kW home uses 1 kW, but when I unplug EV home is only using 0,4kW 0.6kW is being used by something when charging by Solar. When I plug the EV back in get the same 5kW from solar, car using 4kW home jumps upto 1kW.

I think I may have just observed something similar. I plugged into the Tesla Wall connector, and the car was waiting to charge, but the app showed and extra kW or so going to the Home. Then I noticed that the car was purring, the air conditioning was running, as was the display and computer. When I got out of the car, the extra draw went to zero. This happened just today, so I have not had a chance to double check it, but it may be that the app treats charging separately from "phantom" drain.

Any chance this is what you are seeing?

 

[aesculus]

Then I noticed that the car was purring, the air conditioning was running, as was the display and computer. When I got out of the car, the extra draw went to zero.

I don't have charge on solar set but if I am in my MX and the HVAC is on, it will draw from the WC. Turning the HVAC off seems to squelch the WC draw for me.

 

[swedge]

For example if NBC is .04 and NSC is .07 aren't you better off exporting your solar and importing for use, vs using your solar to power home/charge car, when you are over producing in the MWh range?

This of it this way. You are a large net exporter. Consider your last kWh of solar, 2 cases.

If you charge your car with it, you pay nothing and you earn nothing. Free car charging is hard to beat.

But let's try your suggestion. You export the 1 kWh and earn 7¢. But you charge you car with 1kWh, and it costs you retail price, 25¢ these days for Dr. fun. So this way the 1kWh of charging costs 18¢. And PG&E loves you for it.

NBCs are included in all imports as part of the retail "bundled" rate. They only matter if your total net accumulated retail NEM charges are less than the accumulated NBCs, as they did for h2o. So in his case he paid the NBCs and was credited for his net generation. The more he charges on solar, the less he imports, and so the less his NBC. So each kWh of charging on solar saves him the 18¢ plus decreasing his NBC by a bit over 3¢. Cheaper than free!

NBCs are a bit of a head spin. Also they were PG&E's first swipe at killing solar when they were introduced in NEM2. It made the hungry for more, and so along came NEM3, which is not really Net Energy Metering at all.

 

[miimura]

Here’s the way I was thinking about the question posed.
1. Your solar is going to produce the same thing over the course of the year and your overproduction and NSC is the same across both scenarios, assuming that the amount of kWh that you charge your car is the same across scenarios, just the time of day is different.
2. If you charge the car only with surplus solar that would have been exported, you don’t pay any NBCs.
3. If you charge the car overnight, you pay NBCs but the base retail rate is offset by other solar exports during the same rate period.

 

[h2ofun]

This of it this way. You are a large net exporter. Consider your last kWh of solar, 2 cases.

If you charge your car with it, you pay nothing and you earn nothing. Free car charging is hard to beat.

But let's try your suggestion. You export the 1 kWh and earn 7¢. But you charge you car with 1kWh, and it costs you retail price, 25¢ these days for Dr. fun. So this way the 1kWh of charging costs 18¢. And PG&E loves you for it.

NBCs are included in all imports as part of the retail "bundled" rate. They only matter if your total net accumulated retail NEM charges are less than the accumulated NBCs, as they did for h2o. So in his case he paid the NBCs and was credited for his net generation. The more he charges on solar, the less he imports, and so the less his NBC. So each kWh of charging on solar saves him the 18¢ plus decreasing his NBC by a bit over 3¢. Cheaper than free!

NBCs are a bit of a head spin. Also they were PG&E's first swipe at killing solar when they were introduced in NEM2. It made the hungry for more, and so along came NEM3, which is not really Net Energy Metering at all.

I do everything I can to charge the EV during the day if I have excess solar, meaning, the PW's are charged . This time of the year running my heat pumps and like 75% less solar generation, there is no solar left, and I have my batteries at 70%.

 

[Redhill_qik]

But let's try your suggestion. You export the 1 kWh and earn 7¢. But you charge you car with 1kWh, and it costs you retail price, 25¢ these days for Dr. fun. So this way the 1kWh of charging costs 18¢. And PG&E loves you for it.

This isn't the way that NEM2.0 works, but it is close to how NEM3.0 works. Under NEM2.0, the exports get a credit at the retail rate, so if the export was during Off-Peak it would be the same as the Off-Peak import and the $0.25 export credit offsets the $0.25 import charge. If the export was during Peak then it might be $0.47 credit versus the $0.25 charge for importing during Off-Peak. So if you are a net exporter with a negative balance at the true-up it doesn't matter if that number is -$1 or -$2,000 as the amount is reset to zero and you are compensated on your net kWh.

NEM2.0 systems that are not net exporters/generators/producers should only be using Charge On Solar during Off-Peak hours. For NEM3.0 I think that the export compensation is lower than the Off-Peak charges for all but a very limited number of hours on certain days during Peak that it isn't worth worry about, so Charge On Solar would be the preferred mode at all times.

 

[swedge]

Under NEM2.0, the exports get a credit at the retail rate,

Not in this particular case. The context is a customer who is a net generator. Under NEM1 and 2, your exports do get accumulated at the retail rate, but at true-up for a typical net generator, the accumulated total is negative and is NOT paid or credited. Instead the net exported kWh are credited at the NSC rate.

 

[garrity]

Redoing the math it looks like you have to send back roughly 1.46kWh of solar to compensate for each 1kWh you import from grid to break even when using NBC and NSC ( This is for net massive exporter where retail pricing is no longer relevant) So best to utilize the solar for your own needs before exporting to grid.

 

[swedge]

1. Your solar is going to produce the same thing over the course of the year and your overproduction and NSC is the same across both scenarios, assuming that the amount of kWh that you charge your car is the same across scenarios, just the time of day is different.

Any solar generation which you self consume, in real time or from PW, is not exported, and so does not increase your net generation and is not credited for NSC. In fact, PG&E has no idea it happened.

NSCs are only credited to exports in excess of your imports. Since we are discussing NSC, the context is a net generator.

For an account which is not a net generator, CoS saves only the NBCs which are charged on the imports but not credited on the exports. So exporting excess solar in daylight and charging at night costs a bit more than charging directly on excess solar. The same is true of PowerWall charging, but the primary benefit there is changing the imports from peak to off peak periods.

 

[swedge]

Redoing the math it looks like you have to send back roughly 1.46kWh of solar to compensate for each 1kWh you import from grid to break even when using NBC and NSC ( This is for net massive exporter where retail pricing is no longer relevant) So best to utilize the solar for your own needs before exporting to grid.

I think I got it wrong before, because the retail charges for imports are offset by export credits, except for NBCs. So my $0.18 per kWh net cost was incorrect.

You export the 1 kWh and earn 7¢. But you charge you car with 1kWh, and it costs you retail price, 25¢ these days for Dr. fun. So this way the 1kWh of charging costs 18¢. And PG&E loves you for it.

Worse yet, since re-importing reduces your net surplus, you don't earn NSC either.

For certain, NBCs, NSC, MDC, NEM are a head spinner. I keep saying that obfuscation is the real point of all of this. I'm sorry to have added to the confusion. Maybe I can make sense of it later on.

Now it is time for me to walk the dog. She doesn't care about all these numbers, and just wants a wooden stick to chew on. ;-)

 

[Redhill_qik]

Not in this particular case. The context is a customer who is a net generator. Under NEM1 and 2, your exports do get accumulated at the retail rate, but at true-up for a typical net generator, the accumulated total is negative and is NOT paid or credited. Instead the net exported kWh are credited at the NSC rate.

Well this is basically what I wrote except for the "exported kWh are credited at NSC rate". Your net annual kWh are compensated/paid at the NSC rate (or higher with a CCA) when the accumulated retail credits/charges for exports/imports are below $0.

You export the 1 kWh and earn 7¢. But you charge you car with 1kWh, and it costs you retail price, 25¢ these days for Dr. fun. So this way the 1kWh of charging costs 18¢.

Your math here is faulty as it is comparing two different things. You can't take the $0.25 retail charge for an import and then subtract a $0.07 payment for net excess kWh from it to get a $0.18 cost.

Possible scenarios:

• EV could be charged at work is $0.00/kWh, but instead is charged at home. This costs $0.07/kWh because of lower net exports.
• EV is charged at Tesla SuperCharger for $0.38/kWh with no charging at home. This has a net cost of $0.31/kWh ($0.38 - $0.07).

 

[swedge]

Your math here is faulty as it is comparing two different things. You can't take the $0.25 retail charge for an import and then subtract a $0.07 payment for net excess kWh from it to get a $0.18 cost.

Yup, I really screwed that up. Which is what I was saying in my last post. Sorry about that.

I am still trying to sort out the differences between net generators and the rest of us. I actually was a net generator on a one-month true-up in July, when my true-up date got reset. I've got to look that up to clarify my understanding. My only other NEM2 true up was based on NBCs, so comparing the two should help.

Again, I apprize for the faulty reasoning I posted.

 

[getakey]

So what is the answer to the OP. I'm going to be converting from EV1 to EV2 in May

 

[miimura]

So what is the answer to the OP. I'm going to be converting from EV1 to EV2 in May

There's 6 pages here already. What exactly is your question?

I just added more solar, so I've just converted from NEM1 to NEM2. The only change I made was to set the Tesla app to sell 7c/kWh less than the buy price. That is ~10% round trip battery loss (4c/kWh) plus ~3c/kWh NBCs. So far it seems to be doing what I want. The only small thing I don't like is that sometimes it starts to discharge to satisfy house load early in the morning before the sun rises. I would prefer that the batteries not discharge during Off-Peak, particularly when I'm charging the car overnight.

 

[getakey]

There's 6 pages here already. What exactly is your question?

I just added more solar, so I've just converted from NEM1 to NEM2. The only change I made was to set the Tesla app to sell 7c/kWh less than the buy price. That is ~10% round trip battery loss (4c/kWh) plus ~3c/kWh NBCs. So far it seems to be doing what I want. The only small thing I don't like is that sometimes it starts to discharge to satisfy house load early in the morning before the sun rises. I would prefer that the batteries not discharge during Off-Peak, particularly when I'm charging the car overnight.

I read through 6 pages and I don't really see a clear answer

 

[swedge]

When charging on solar there is no NBC since you're not importing anything. So it costs you nothing and you gain nothing.

But if you export 1kW solar you get aprox .07 from PGE at true up.
If you charge at night 1kW it costs you .04 for NBC so net if you exported 1kW during day and charged 1kW at night you net gain .03. Is this correct?

Again, this is assuming massive overproduction.

After much head scratching (I am bald now) and dog walking, I am pretty sure you were correct.

For a net generator on PG&E's EV2A and NEM2, with solar, PowerWall and an EV, it is more beneficial to charge the car at night rather than on excess solar during the day.

Car charging on excess solar during the day has no direct impact on the bill, but it does prevent exporting that energy, decreasing the NSC compensation.

Nighttime charging does increase the NBC total. When charging during the day, the NEM balance is debited at the retail price, but wince the balance is below zero at true-up, it is ignored.

Per a recent true-up and the EV2 tariff effective 6/30/23, NSC is running $0.08158 and NBCs are costing $0.03273 per kWh. So for each kWh of car charging at night, your PG&E bill will be lower by $0.04885 nearly 5¢. Of course PG&E will likely change these numbers going forward, but maybe not by much. We hope.

This is not true for us net consumers whose solar over a year underproduces relative to our consumption. This is yet another way in which the optimum strategy for using our PWs depends on the details of our situation.

H2ofun, please take note. Getakey also.

SW

 

[h2ofun]

After much head scratching (I am bald now) and dog walking, I am pretty sure you were correct.

For a net generator on PG&E's EV2A and NEM2, with solar, PowerWall and an EV, it is more beneficial to charge the car at night rather than on excess solar during the day.

Car charging on excess solar during the day has no direct impact on the bill, but it does prevent exporting that energy, decreasing the NSC compensation.

Nighttime charging does increase the NBC total. When charging during the day, the NEM balance is debited at the retail price, but wince the balance is below zero at true-up, it is ignored.

Per a recent true-up and the EV2 tariff effective 6/30/23, NSC is running $0.08158 and NBCs are costing $0.03273 per kWh. So for each kWh of car charging at night, your PG&E bill will be lower by $0.04885 nearly 5¢. Of course PG&E will likely change these numbers going forward, but maybe not by much. We hope.

This is not true for us net consumers whose solar over a year underproduces relative to our consumption. This is yet another way in which the optimum strategy for using our PWs depends on the details of our situation.

H2ofun, please take note. Getakey also.

SW

I am reading.

Since solar is so law this time of the year, and I use so much with my heat pumps, I set my storage at 70%, and still have a hard time getting the PW's back to 100%. I do get them to used for the 4 to 9 high cost period.

I have now just plugged the EV in during the day, and charge before 4. Whether I do this, or charge after 10pm, all seems the same since the cost is equal.

What is SO nice about having way too much solar is I do not need to spend anytime trying to save a few pennies. I just want it easy for my wife to just drive the tesla, and I want the house warm for her and my Dad. With my excess solar, its a piece of cake to meet these objectives.