Inverter with Limiter

[fafrd]

I have never heard of that before. I have two properties on NEM 1.0 with SCE. The only thing that can kick you off NEM 1.0 is increasing your solar capacity. The EV rate is a tariff and you are free to change tariffs within a NEM agreement

Check with your utility. At least with mine (PG&E), they were very clear - if I want to switch of of my current no-longer-available solar rate plan, that will move me from NEM1 to NEM2.

In addition, I’ll get even less credit for my solar generation and the power I do consume when solar is inactive will cost me more.

And to top it all off, I’ll need to add more than 1kW of solar to cover consumption of an EV, which kicks me off of NEM1 anyway.

Solving time-shift with a new DC-coupled array offers so much more freedom than trying to expand my grid-tied system. I was all set to do this with a hybrid inverter when the cost/complexity or rewiring the subpanels became a barrier as well as the cost of getting all UL-certified components. And finally, a new critical piece of high-technology equipment upon which the functioning of the entire house depends.

So that’s why these current-limited inverters tied in in parallel with the grid has suddenly become so attractive to me (if it can be made to work).

 

[Ampster]

The "Duck's Back" curve is a lie.

I agree it does not capture residential solar production because that only shows up as net consumption on the grid. I am sure the 30 kWhrs I generator during a good day in the summer never makes it past the transformers on my block.

I want to call a solar strike. Some hot summer afternoon at 2:30 PM, we all shut off our inverters. And we don't turn them back on until a new pricing schedule has been negotiated, crediting us for our surplus based on what PG&E had to pay to buy that power from another source.

I am hopeful that at some point we can aggregate our inverters and sell back to the grid at Peaker rates. Tesla is actually doing that in Australia and Vermont or New Hampshire. They have applied to the CPUC to be a load serving entity and with their software may be able to be a virtual power plant. We are in a great period of transition.

 

[Hedges]

I got 8 280Ah LiFePO4 cells for $93.59 each (with shipping), so $104.45/kWh.

So it’ll take me 4.5 years to break-even on the battery, but I needed it anyway for backup during fire outages.

If you cycle the battery 80% once per day for 10 years, amortized cost $0.04/kWh
(neglecting BMS and inverter)
Maybe it is good for that many cycles, maybe twice as many.
So yes, that is pretty cost effective.

Could you add more PV panels aimed at morning sun, extend the hours you backfeed with net metering but not increase peak watts?

You can generate a kWh for $0.05 and store it until evening for $0.04, costs you $0.09 for an evening kWh.
You can give the utility two kWh in the morning for $0.10 and get one kWh in the evening.
The two seem equal in cost.

Good to have backup during power failures. Are you able to operate within the system's limits? It's pretty small.
The dent it will make in your peak consumption is small too.

Charging EV is going to make sense if you either are at home during sunshine hours, or can use net metering to store PV production for nighttime charging.

I think I'm due to get pushed onto NEM 2.0 in a couple years. So long as we continue to get net metering rather than "sell low, buy high"

 

[Ampster]

Check with your utility. At least with mine (PG&E), they were very clear

I never ask my utility those kind of questions. They have no incentive to give me the correct answer. Issues like this have been discussed on forums like the teslamotorsclub.com ad nauseum. Here is the result of just one google search.

A Guide to Grandfathering Protections for Solar Customers

www.energytoolbase.com

My point is not to argue or tell you that you are wrong. I am trying to help you understand your rights. It is all in your NEM agreement. The underlying concept of NEM 1.0 has nothing to do with the tariff (rate plan) that you choose. It has everything to do with you being paid for generation at the rate that is in affect when you generate. All NEM 1.0 does is protect you from being charged Non Bypassable Charges (NBC} which are what were added to NEM 2.0

 

[Ampster]

I think I'm due to get pushed onto NEM 2.0 in a couple years.

When did you go on NEM 1.0? I thought the grandfathering was something like 20 years?

 

[GXMnow]

fafrd, This might do what you are looking for.

Amazon.com

This is a 1000 watt that will accept 22 to 65 volts DC and drives 1120 volt out. So you just put one on each leg of the 120/240 split phase. No Autotransformer needed. Each one will just limit it's leg to zero export. It is meant to work direct from a solar panel, but reading the reviews, there are some people running it from a battery bank. I have not used these, so I have no idea how good they might be. You may need to add some kind of timer control to keep it from running down the batteries overnight.

Hedges, I know what you mean. The later time peak rate is totally a "Stick it to Solar" money grab. But thanks to my battery bank now, I will just zero out my meter during the peak rate time, no matter when they set it. If solar production is low, I just charge off the grid and make them buy it back at twice the price in the evening. Oops, did I say that? In reality, with just a useable 15 KWHs of storage, I have yet to battery export more than the solar generated on any day. And I am not "exporting" much at all lately. When the sun is up, I am charging so export never exceeds 1,000 watts. And in the evening, I have the battery pushing 1,400 watts into my panel, but the house is using most of it. For the last few colder days, with my furnace kicking on, my export from battery tops out less than 500 watts, totaling maybe 1.8 KWH back to the grid during the 5 hour peak rate time.

I also agree, even with so many of my neighbors having solar now, with many of their systems bigger than mine, we just self powering a few blocks. We are not pushing back to the sub station, let alone back to the generating plants. Except for having to manually set my XW-Pro for now, I am putting the least demand on the grid of anyone around me. Since I do not need my A/C n this cold weather, my draw from the grid never tops 2,000 watts, and my feed back to the grid never tops 1,000 watts. With 8 more panels and 50% more battery, I could go off grid. But that would work the batteries a lot harder, and increase my cost over time with shorter battery life. My battery bank is working great for now, going from 85% down to 45% every evening, and charging back up to 85% the next morning to afternoon off of the sun. It was cool and sunny all day, so even in December, my 16 panels produced 16.9 KWHs from 7:30 am to 4:15 pm. That is a solid 3.5 "Sun Hours". Peak output hit 3,100 watts at 12:15 pm.

I am stuck on NEM 2.0 but I have to admit, the NBC's are not too bad at this point. It was just over $7.00 for Nov. 18 - Dec. 17. The power I used cost me another $43.00 making the bill $50.44 for 252.9 KWH. $0.1994 per KWH including all taxes and NBC's etc. I used more off peak power, but they credited me for $11.60 for the $0.42 mid peak power I sent back to them in the evening with the battery. In the same time period in 2018 before the solar went in, I consumed 720 KWHs compared to the 253 KWHs now. That is 65% of my power being supplied by solar now. Once I get on the "Prime D" rate for having the battery bank, it should take my cost down from 20 cents to 15 cents per KWH. And just as I calculated before, I need 50% more solar to go zero grid, or off grid.

 

[fafrd]

I never ask my utility those kind of questions. They have no incentive to give me the correct answer. Issues like this have been discussed on forums like the teslamotorsclub.com ad nauseum. Here is the result of just one google search.

A Guide to Grandfathering Protections for Solar Customers

www.energytoolbase.com

My point is not to argue or tell you that you are wrong. I am trying to help you understand your rights. It is all in your NEM agreement. The underlying concept of NEM 1.0 has nothing to do with the tariff (rate plan) that you choose. It has everything to do with you being paid for generation at the rate that is in affect when you generate. All NEM 1.0 does is protect you from being charged Non Bypassable Charges (NBC} which are what were added to NEM 2.0

I appreciate all of your inputs and points. I also probably should spend more time researching how others have navigated this stuff.

I can just share my experience. I signed up to NEM1 before the existence of NBCs. After less than a year of going Active, I was informed I’m now going to be charged $10/month for ‘network access’ which is non-refundable. Now, if my consumption exceeds my annual generation credit, that $120 in non-refundable network access charges credits against my true-up, so perhaps I have it better than someone on NEM2 and perhaps those additional charges are not true NBCs. But since my system is sized to cover just over 100% of consumption, annual electrical bills of $700 have dropped to $120 rather than $0 as they were supposed to.

And now they are shifting the peak time of use window from 50% overlapped with the solar production window to less than 10% overlapped (and moving most of my actual consumption in the evening from off-peak window to peak window).

I appreciate your approach of not asking questions but I’ve asked enough to know the utility will use any excuse to move me off of my NEM1 agreement to NEM2 (which essentially translates to taxes owed on everything you consume from the grid, regardless of whether you’be got generation credit to cover that consumption or not.

So leaving what I have alone and finding a way to quietly self-consume what I generate with a few new panels just seems like the more prudent way to go..,

 

[Ampster]

I can just share my experience. I signed up to NEM1 before the existence of NBCs. After less than a year of going Active, I was informed I’m now going to be charged $10/month for ‘network access’ which is non-refundable.

They are not NBCs, they are MDCs (Minimum Delivery Charges). LOL. I now get them on my NEM 1.0 statements also. The year end credit should offset them but the payback on energy credits is reduced by 90% so it doesn't matter. I have always had EVs and so my solution to that under NEM 1.0 was just to charge more at night burning off the credit I earned during the day at three times the rate. I think of them as fixed charges and my opinion is that fixed charges will continue to erode the benefit of solar. But there is hope and a lot of things we can do behind the meter to keep the cost of energy as low as possible. I believe batteries are an important part of that.

 

[Hedges]

When did you go on NEM 1.0? I thought the grandfathering was something like 20 years?

About 2003.
So it'll have been 20 years in 2023.

Electric rates aren't my biggest problem anymore. It's my water bill.
(well, after my property taxes, of course)

 

[Ampster]

So it'll have been 20 years in 2023.

Wow you should get a gold medal. I bought 2.5 kW of BP panels in 2009 for $5.00 per Watt because I thought prices were going up. LOL

Electric rates aren't my biggest problem anymore. It's my water bill

Yes, I have captured some rain off my roof and my next project is to add more storage and flush my toilets with that. Maybe even capture some grey water and use it for irrigation in addition to the rain water. I was amazed at how much just one side of my roof would produce with just 1 inch of rain.

 

[fafrd]

If you cycle the battery 80% once per day for 10 years, amortized cost $0.04/kWh
(neglecting BMS and inverter)
Maybe it is good for that many cycles, maybe twice as many.
So yes, that is pretty cost effective.

Could you add more PV panels aimed at morning sun, extend the hours you backfeed with net metering but not increase peak watts?

Perhaps, but that would violate my agreement and risks being forced into NEM2. Also, since the utility now has a history of my annual production, it would be trivial for them to figure out that something has changed without me informing them.

You can generate a kWh for $0.05 and store it until evening for $0.04, costs you $0.09 for an evening kWh.
You can give the utility two kWh in the morning for $0.10 and get one kWh in the evening.
The two seem equal in cost.

Good to have backup during power failures. Are you able to operate within the system's limits? It's pretty small.
The dent it will make in your peak consumption is small too.

I can see my hourly consumption but not peak. Hourly, I’m averaging less than 1.5kWh/hour, so 2kW of inverter capacity should be enough to offset pretty much everything,

The electric oven burns 3kW when the element is being fired, so I’ll need boost from the grid when that fires up (which is only occasionally).

People claim the 2kW inverters are less reliable than the 1kW models ardbthey require a 48V battery compared to the 1kW model which can run off of either 24V or 48V batteries, so I’m kind of on the fence over whether I want to stick to 1kW per phase or move up to the 2kW model...

One nice thing about having the grid and inverters connected in parallel is I don’t need to worry about startup surge of motors (fridges, washing machine, dishwasher).

Charging EV is going to make sense if you either are at home during sunshine hours, or can use net metering to store PV production for nighttime charging.

I think I'm due to get pushed onto NEM 2.0 in a couple years. So long as we continue to get net metering rather than "sell low, buy high"

The biggest change appears to be the ~10% tax on all energy drawn from the grid.

The sell low buy high is being imposed on all solar customers starting next year (NEM1 included) - pretty much all solar production is being moved to off-peak while pretty much all evening and nighttime consumption is being moved to peak.

 

[fafrd]

fafrd, This might do what you are looking for.

Amazon.com

This is a 1000 watt that will accept 22 to 65 volts DC and drives 1120 volt out. So you just put one on each leg of the 120/240 split phase. No Autotransformer needed. Each one will just limit it's leg to zero export. It is meant to work direct from a solar panel, but reading the reviews, there are some people running it from a battery bank. I have not used these, so I have no idea how good they might be. You may need to add some kind of timer control to keep it from running down the batteries overnight.

Hedges, I know what you mean. The later time peak rate is totally a "Stick it to Solar" money grab. But thanks to my battery bank now, I will just zero out my meter during the peak rate time, no matter when they set it. If solar production is low, I just charge off the grid and make them buy it back at twice the price in the evening. Oops, did I say that? In reality, with just a useable 15 KWHs of storage, I have yet to battery export more than the solar generated on any day. And I am not "exporting" much at all lately. When the sun is up, I am charging so export never exceeds 1,000 watts. And in the evening, I have the battery pushing 1,400 watts into my panel, but the house is using most of it. For the last few colder days, with my furnace kicking on, my export from battery tops out less than 500 watts, totaling maybe 1.8 KWH back to the grid during the 5 hour peak rate time.

I also agree, even with so many of my neighbors having solar now, with many of their systems bigger than mine, we just self powering a few blocks. We are not pushing back to the sub station, let alone back to the generating plants. Except for having to manually set my XW-Pro for now, I am putting the least demand on the grid of anyone around me. Since I do not need my A/C n this cold weather, my draw from the grid never tops 2,000 watts, and my feed back to the grid never tops 1,000 watts. With 8 more panels and 50% more battery, I could go off grid. But that would work the batteries a lot harder, and increase my cost over time with shorter battery life. My battery bank is working great for now, going from 85% down to 45% every evening, and charging back up to 85% the next morning to afternoon off of the sun. It was cool and sunny all day, so even in December, my 16 panels produced 16.9 KWHs from 7:30 am to 4:15 pm. That is a solid 3.5 "Sun Hours". Peak output hit 3,100 watts at 12:15 pm.

I am stuck on NEM 2.0 but I have to admit, the NBC's are not too bad at this point. It was just over $7.00 for Nov. 18 - Dec. 17. The power I used cost me another $43.00 making the bill $50.44 for 252.9 KWH. $0.1994 per KWH including all taxes and NBC's etc. I used more off peak power, but they credited me for $11.60 for the $0.42 mid peak power I sent back to them in the evening with the battery. In the same time period in 2018 before the solar went in, I consumed 720 KWHs compared to the 253 KWHs now. That is 65% of my power being supplied by solar now. Once I get on the "Prime D" rate for having the battery bank, it should take my cost down from 20 cents to 15 cents per KWH. And just as I calculated before, I need 50% more solar to go zero grid, or off grid.

That’s exactly the zero export inverter I’m considering, but the 120V model is dubious - others say it wiggles one leg around neutral (meaning 1kW is only 0.5kW @ 120V.

If the core inverter is designed for 2-phase 240V, it’ll be easier to not fight that and just work with it.

Are you using one/several of these and if so, which exact model and connected how?

 

[GXMnow]

I looked into those inverters, but ended up getting the Schneider XW-Pro instead.

The model I had picked is rated to directly output just one phase of 120 volt. Having two of them, one on each leg should be fine. I do not see any reason why it would have any "wiggle" issue. My big 6,800 Watt Schneider is a single inverter with an autotransformer to make the 120/240 volt split phase. This has a limitation in that it has to feed power to both legs. When it is in "Grid Sell" mode, it is pushing equal current out of both legs. So if I have only 200 watts on one leg, and 2,000 watts on the other leg, it could put out 2,200 watts, but one leg would be selling 900 watts, and the other leg is still buying 900 watts. I am not sure how my power meter would treat that. Having 2 separate inverters would not have that problem. I almost went with 2 Magnum inverters for this reason. But as it turns out, my basic constant home load is pretty well balanced so it is working well. Hopefully I will soon be able to move my essential loads to the backup panel. I have to shut down all of my computers so I can cut power and trace out the lines and move them.

 

[Hedges]

Could you add more PV panels aimed at morning sun, extend the hours you backfeed with net metering but not increase peak watts?

Perhaps, but that would violate my agreement and risks being forced into NEM2. Also, since the utility now has a history of my annual production, it would be trivial for them to figure out that something has changed without me informing them.

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

"Modifications (7) . REGFs eligible for the 20-year transition period outlined above that are modified and/or repaired shall remain eligible for the remainder of their 20-year transition period as long as the modifications and/or repairs do not increase the REGF by more than the greater of: 1) 10 percent of the REGF’s nameplate rating capacity, as established when the REGF was originally interconnected, or 2) 1 kW; and provided the modifications and/or repairs do not result in the REGF exceeding the Customer’s annual onsite load."

"(7) Customers making modifications and/or additions to their REGF that exceed the 10 percent or 1 kW limit referenced above have the option of either metering the additions and/or modifications separately under another eligible tariff or other authorized process, or having the entire REGF served under another eligible tariff, subject to the terms and conditions contained therein. This requirement will only be enforced upon the development of a new NEM Successor Tariff that supersedes D.16-01-044, or by the direction of the CPUC."

That says "kW", not "kWh"

You have inverters that comply with your "Permission to Connect" letter.
If you over-paneled, that wouldn't change "nameplate rating capacity", the kW you put into the grid.

You could even replace the inverter(s) with another rated 1 kW higher.

 

[fafrd]

I looked into those inverters, but ended up getting the Schneider XW-Pro instead.

The model I had picked is rated to directly output just one phase of 120 volt. Having two of them, one on each leg should be fine. I do not see any reason why it would have any "wiggle" issue. My big 6,800 Watt Schneider is a single inverter with an autotransformer to make the 120/240 volt split phase. This has a limitation in that it has to feed power to both legs. When it is in "Grid Sell" mode, it is pushing equal current out of both legs. So if I have only 200 watts on one leg, and 2,000 watts on the other leg, it could put out 2,200 watts, but one leg would be selling 900 watts, and the other leg is still buying 900 watts. I am not sure how my power meter would treat that. Having 2 separate inverters would not have that problem. I almost went with 2 Magnum inverters for this reason. But as it turns out, my basic constant home load is pretty well balanced so it is working well. Hopefully I will soon be able to move my essential loads to the backup panel. I have to shut down all of my computers so I can cut power and trace out the lines and move them.

I was debating between a ConextSW and a Magnum PAE for my prime-time build. I had not considered using an inverter of that class in a parallel configuration, but I don’t believe they support external limiting sensors and so need to be wired into the main current path, correct? Plus, they are much pricier.

I know the ratings in those GTIL inverters. I also know that several owners claim that they are all true 240V inverters and of ‘Autodetect’ means just driving (‘wiggling’ ) one leg when it senses that the other leg is tied to ground, that translates to 1/2 of the rated power output (as other owners have claimed).

There are owners successfully using those inverters to drive 240V at close to rated power output, so spending a few more $$$s to assure the full rated (and limited) power output is delivered into the correct leg seems like a better path than screwing around trying to make something work that others have struggled with.

Seem to be no owners here, but there is apparently a Facebook Group where you can read all the horror stories.

The Autoinverters I’m considering cost only $70 each: https://voltage-converter-transform...0-220-voltage-converter-transformer-1500-watt

I could try purchasing two of the 120V models, stack two of them with common neutral, and check if they work, but to save only $140 versus the much more certain alternative, I’m not sure it’s worth it.

Plus, with the Autoinverters, only UL listed equipment is connected directly to the grid.

 

[fafrd]

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

"Modifications (7) . REGFs eligible for the 20-year transition period outlined above that are modified and/or repaired shall remain eligible for the remainder of their 20-year transition period as long as the modifications and/or repairs do not increase the REGF by more than the greater of: 1) 10 percent of the REGF’s nameplate rating capacity, as established when the REGF was originally interconnected, or 2) 1 kW; and provided the modifications and/or repairs do not result in the REGF exceeding the Customer’s annual onsite load."

"(7) Customers making modifications and/or additions to their REGF that exceed the 10 percent or 1 kW limit referenced above have the option of either metering the additions and/or modifications separately under another eligible tariff or other authorized process, or having the entire REGF served under another eligible tariff, subject to the terms and conditions contained therein. This requirement will only be enforced upon the development of a new NEM Successor Tariff that supersedes D.16-01-044, or by the direction of the CPUC."

That says "kW", not "kWh"

You have inverters that comply with your "Permission to Connect" letter.
If you over-paneled, that wouldn't change "nameplate rating capacity", the kW you put into the grid.

You could even replace the inverter(s) with another rated 1 kW higher.

Well first, even when adding 1kW of output, they require the plan to be reviewed and approved if you are exporting to the grid. It’s not like you can just start exporting another 1kW of energy whenever you want - the utility needs to review and approve any equipment exporting to their grid.

Second, I am planning to have 2kW of inverters and they will be battery powered, not PV-powered.

And lastly, after having spoken to them, the utility is extremely concerned about any equipment that will be exporting to their grid, but pretty much not concerned about equipment including PV, inverters, and batteries being used for self-consumption and never exporting to their grid.

$140 to avoid the possibility of getting into an argument/dispute with my utility is a no-brainer to me.

 

[Hedges]

Plus, with the Autoinverters, only UL listed equipment is connected directly to the grid.

And I have a UL listed main breaker panel as the only thing connected directly to the grid.
That doesn't mean that a non-UL1741 inverter wired to it would electrocute the lineman any less.

Your "Autoinverter" is probably an auto-transformer, not isolation, so that doesn't even galvanically isolate the inverter from the grid.
Not that isolation would make any difference.

 

[Hedges]

Well first, even when adding 1kW of output, they require the plan to be reviewed and approved if you are exporting to the grid. It’s not like you can just start exporting another 1kW of energy whenever you want - the utility needs to review and approve any equipment exporting to their grid.

Second, I am planning to have 2kW of inverters and they will be battery powered, not PV-powered.

And lastly, after having spoken to them, the utility is extremely concerned about any equipment that will be exporting to their grid, but pretty much not concerned about equipment including PV, inverters, and batteries being used for self-consumption and never exporting to their grid.

$140 to avoid the possibility of getting into an argument/dispute with my utility is a no-brainer to me.

I think the point of 1kW is you're allowed to install replacement equipment. Maybe exactly same size inverter isn't available, so OK to go up slightly. I don't think any plan/review/approval is required to replace one UL listed inverter with another, within that 1 kW limit. The new one also doesn't have to be the latest "Rule 21" etc., you can put in an old model.

I think they should be concerned about zero export, needs to be something UL or other NRTL tested to make sure it really doesn't export.
That's different from UPS which never puts power on the wires PG&E is simultaneously feeding.

If you can accomplish the peak shaving economically, good enough.
Got any loads you can switch off with a timer?

 

[fafrd]

And I have a UL listed main breaker panel as the only thing connected directly to the grid.
That doesn't mean that a non-UL1741 inverter wired to it would electrocute the lineman any less.

Your "Autoinverter" is probably an auto-transformer, not isolation, so that doesn't even galvanically isolate the inverter from the grid.
Not that isolation would make any difference.

Yeah, I should have said ‘directly electrically’ connected (ie:: sharing electrons).

And that’s the second time I used Autoinverter where I meant Autotransformer today.

 

[fafrd]

I think the point of 1kW is you're allowed to install replacement equipment. Maybe exactly same size inverter isn't available, so OK to go up slightly. I don't think any plan/review/approval is required to replace one UL listed inverter with another, within that 1 kW limit. The new one also doesn't have to be the latest "Rule 21" etc., you can put in an old model.

I specifically asked my utility that question and from their response, it’s clear to me they think differently than you do.

Approval should be close to automatic, but they expect a new application to be submitted and to review any equipment changes.

I think they should be concerned about zero export, needs to be something UL or other NRTL tested to make sure it really doesn't export.
That's different from UPS which never puts power on the wires PG&E is simultaneously feeding.

If you can accomplish the peak shaving economically, good enough.
Got any loads you can switch off with a timer?

It’s more than peak shaving, it’s using additional solar generation to self-power rather exporting to the grid (without rewiring everything and having a new piece of complicated electrical equipment in the critical path).