Adding off-grid panels and batteries to existing grid-tied system

[apachexmd]

I have an existing 4kw system with a SolarEdge SE3800 inverter in California. I would like to add an additional 3000w-5000w in panels and a large battery, without violating my existing net metering agreement.

I was thinking of adding a AC coupled 15kw Sigineer inverter. This would feed a critical loads panel (which would be most of the house loads). I would relocate the existing SolarEdge tie-in to the critical loads panel.

The battery would be a large bank made of used 48v BYD LiFePo packs. I would also our purchase a new high voltage charge MPPT charge controller for the new panel array. The new panel array will be connected only to the new charge controller. Hopefully the batteries can be charged in parallel from both the grid (via the Sigineer's built-in AC charger) and solar (via the new array and charge controller.

The idea is to be as energy independent as possible. I have 2 EVs and the existing 4kw solar just isn't enough to provide all the juice I use.

With the large battery and the large 15kw inverter, I hope to run off of solar during daylight hours (small loads and battery charging), and at night be completely on battery power (including EV charging). I still need to make usage measurements so I can properly size the battery and new solar array but I was thinking about a new 3500w solar array and a 30kwh battery.

Will this setup do what I want?

 

[snoobler]

30kWh feels way too small to charge EVs and run a house. Consider that if you're sizing your inverter for the loads, that battery will only power it for 2 hours at max, and IIRC, a 50A Class 2 charger can pull 12kW.

However, I think you have the concept correct. I don't know that I'd trust a Sigineer for the job, nor do I know if it works while AC coupled - not knocking them, but given the scale of the project, I'd go with something high end.

Lastly find out how well your existing grid-tie configuration performs with AC coupled inverters. Some don't like to synchronize so much.

 

[apachexmd]

Thanks for the insight. I still need to do a more detailed load analysis to make sure I won't prematurely run out of battery, but the gist is that the inverter is sized for max load but I don't anticipate on running full load for very long except on rare occasions.

I am also considering something like the Outback Skybox but it's a much smaller inverter for more money so I will have to be much more selective with my loads and EV charging off batteries would be a no go.

Another thing that is a little hazy, is if the Sigineer is AC coupled to my existing grid-tied inverter and the grid is UP, and the battery is FULL, would I still be able to have the grid tie inverter sell to he grid?

I understand that in a power outage, I need to shut down the grid tie inverter when the batteries are full, but I do NOT want to shut down the grid-tied when I could be selling to the grid. I do not need to sell to the grid from the batteries, just from the existing grid tied system.

 

[snoobler]

Pretty sure you're not compromising your ability to sell back to the grid once you have a surplus.

AC Coupling

AC Coupled Solar Power System - use your existing system to feed power into a battery based inverter/charger to charge the battery bank.

www.altestore.com

 

[newbostonconst]

If you get a hybrid inverter you can charge, run off solar, critical loads and grid or no grid all at the same time with one unit.

Here is a good list of most of them.

Hybrid Inverter | Hybrid Solar Inverter | altE

Hybrid inverters, mostly used in grid-tie solar systems, can provide backup power when the electric grid fails. Call 877-878-4060 to size your system today.

www.altestore.com

 

[SolarQueen]

Take a look at the Schneider XW Pro 6848 for your AC Coupling.

 

[apachexmd]

With the Conext XW Pro, I would need two units in a multi unit configuration to supply my desired panel load. I would still need an external charge controller if I am adding a second panel array, correct? And I would need the Conext Gateway?

If I went with something like the Outback Skybox, MPPT is built in, and there's no need for an separate device just to get commissioned.

Is there a particular reason why the Conext XW would suit me better than the Sigineer or an outback sky box (besides Sigineer's lack of UK listing)?

 

[apachexmd]

Pretty sure you're not compromising your ability to sell back to the grid once you have a surplus.

AC Coupling

AC Coupled Solar Power System - use your existing system to feed power into a battery based inverter/charger to charge the battery bank.

www.altestore.com

I emailed Sigineer about this, and his reply to my question is as follows:

If I have my grid-tied inverter AC coupled to the AC output of the
HP15048D, will the grid-tied inverter still be able to sell power back
to the grid?

Yes and NO, because the AC output of the HP15048D can only be
connected to load, not grid, the power will be consumed by the loads.
If you want to sell power, you have to install a transfer switch to
switch the grid tie inverter to the grid.

So if the Sigineer is in battery mode (inverter inverting), it doesn't sound like I would be able to sell back to the grid without physically reconnecting the grid-tied inverter to the grid (instead of tied to the AC output of the Sigineer). Or manually put the inverter into AC bypass mode.

This is inline with this project here which is using the same 15KW Sigineer that I'm considering. It sounds like he keeps his Sigineer in "AC Priority" mode which is essentially having it in bypass mode until a power outage occurs, so grid AC is passing straight through to the AC output side of the inverter. In this mode, his grid tied inverter is able to sell to the grid. He installed a contactor to disconnect the grid from the Sigineer forcing it to battery-mode, and only then can his grid-tie inverter charge the batteries. When batteries are full, the contactor reconnects the grid, and the grid-tied inverter is once again able to sell to the grid. He is using a custom made Raspberry pi controller to control the grid on/off contactor, and control a modified portion of the battery charging circuit to enable/disable battery charging.

This is all extra steps and custom controls that I am definitely not willing to do.

And as such, I'm more and more leaning toward something like the Outback Skybox. While it has less inverter capacity, it makes up for it in flexibility, and (hopefully) support. I like how it has built in MPPT for my second array vs the Schneider Conext series, and has a lot of flexibility in terms of time of use and peak shaving. Any cons or pitfalls I should know about before diving headfirst with the Skybox?

 

[Ampster]

I am very happy with my Outback Skybox and it AC couples with my SE 3800 very easily. The best thing about the Skybox is it is All in One so you don't need any additional communication devices. I paid $6000 for mine but they have been discounted to $3500 at most retailers. With 28 kW of LFP batteries it has allowed me to run the critical loads panel off the grid and still have enough extra solar later in the afternoon to charge two EVs. I have an EVSE that I can adjust the charging current on so when I am charging off solar I only set it at 16 Amps. If I need more during super off peak rates I can always increase the Amps overnight.

By the way, I have researched this extensively and all you need is a building permit to install a Skybox because it is behind the meter. Even better is your NEM agreement probably allows you to add 1kW of capacity with your existing NEM agreement so when I AC coupled I set the Skybox to only export 4.8 kW so I can stay withing my arrangement but still get credit for any excess that I am not using.

 

[Ampster]

I understand that in a power outage, I need to shut down the grid tie inverter when the batteries are full, but I do NOT want to shut down the grid-tied when I could be selling to the grid. I do not need to sell to the grid from the batteries, just from the existing grid tied system.

No during a power outage the Skybox will control your GT inverter and you could conceivably charge your EVs, As I mentioned earlier I don't find a need to charge at the full 40 Amps that my EVSE can put out.

And as such, I'm more and more leaning toward something like the Outback Skybox. While it has less inverter capacity, it makes up for it in flexibility, and (hopefully) support. I like how it has built in MPPT for my second array vs the Schneider Conext series, and has a lot of flexibility in terms of time of use and peak shaving. Any cons or pitfalls I should know about before diving headfirst with the Skybox?

I did not see your last post before my response above. I think you are correct in your analysis of the Sigineer. I think the operative issue is whether is is UL 1741SA compliant as well as CA Rule 21. The Skybox complies with all of those.

I assume in California you are with one of the IOUs for my earlier comments to be correct. Certain Public or Municipal utilities may have different rules as far as NEM agreements that I have not researched. What part of California are you located in?

The Skybox has met all of my expectations and it was designed from the ground up to be a grid interactive inverter. I had a deposit on a couple of Tesla Powerwalls and cancelled that because I was convinced I could get a better value from the Skybox and I have had no regrets. At another home I had an Outback Radian and the service is excellent, The user forum at Outbackpower.com is also helpful.
Please ask any specific questions you may have.

 

[apachexmd]

Thanks for your input Ampster. I've read many of your posts. I think I am in a similar situation where you once were, with similar goals.

I'm in the San Francisco Bay Area under PG&E but am still under NEM1.0. I've dug up my signed copy of the NEM agreement and I can't find where it limits solar production to a certain number of KW. Where did you find the additional 1KW number?

With the skybox are you able to customize battery charging voltages? Let's say I want to top off lithium ion cells to 4.1v instead of 4.2v per cell, can I do that?

Were you able to get your BMS talking to the Skybox via canbus? Batteries/BMS's is another thing that I think I need to do more research on.

 

[GXMnow]

I have an Enphase grid tie system with 4,800 watts of panels, and it can make over 3,800 watts of AC to my panel. I have seen the inverters go into power clip for a bit and I can top 30 KWH's in a day when it is not stupid hot out. Typical average is probably 26 KWH's a day. I was pushing a fair bit back to the utility, only to buy it back in the evening.

I recently installed a Schneider XW-Pro that I did get through Real Good (The California arm of Alt E Store). I only have 17 KWH of storage on it right now, made from 3 LG Chem Chevy Bolt car modules. The whole car uses 10 modules. The XW-Pro does require the Conext Gateway to set it up, but in the scheme of this project the cost is not bad. I have to say for a stout inverter/charger, the XW-Pro is an absolute beast. The continuous rating is 6,800 watts, but it will not skip a beat doing that all day long. The 30 minute rating is 8,500 watts and it can peak to 12,000 watts for 30 seconds for motor start etc. If that is not enough power, you can gang 2 or more for serious power. And they can be ganged to the same load and also sell power to grid which many inverters this size won't do. I have found a few little software issues, but if you are going to have some DC coupled solar, you should not have a problem. I am documenting my system in a Show and Tell thread titled "Adding Storage to my Enphase System". I have not figured out how to link a different thread yet. Since I only have the AC coupled solar, I am working on a programmable logic controller to command the XW on when to change modes and adjust the charge and invert currents. Hopefully Schneider will fix this in a software update, but I am not holding my breath, and trying to do it on my own. To add the DC coupled solar, yes, you need to also get an MPPT controller. The Schneider MPPT 80 600 is a bit pricey, but it takes up to 600 volt open circuit on the panel side, and can charge the batteries at up to 80 amps on the output side. That is over 4,000 watts of output on a 50 volt battery bank.

They do have some BMS integration options with packaged battery units, but mine is not tied in. I don't think it is that important. You have full control over the voltages and currents, and I have it set to stop charging and shut down inverting well inside of the BMS limits, so it should never have to cut off unless the battery is failing and goes way out of balance. You can ad the Schneider Battery Monitor unit to get a more accurate State of Charge on the battery, and it can sense a mid pack voltage that may help it detect if it is going out of balance, but again, the BMS will shut down if the balance goes out so it's not a safety concern. My BMS has a blutooth app, I check in on the pack once in a while and it has been working great. The balancer section rarely has to do anything.

What is the capacity of your electric cars, and how far do you run them down in a day?
Let's assume a little...
If you have a 60 KWH car like most of the newer ones (Chevy Bolt, Nissan Leaf, Tesla 3 Kia Niro EV), and you use say 30%, that means you still need about 20 KWH's to top it back up each night. And that is each car. That is more than 60 miles of driving per car. A BMW i3 or a Chevy Volt is a bit less battery to charge. A Tesla 100 model or Porsche Taycan, a bit more.

If you set it to charge that 20 KWH's in 6 hours, as you sleep, that is charging at about 3.4 KW's per car. The great thing about the XW-Pro for this use, is you can set it in "Grid Support Mode" where it will just add it's 6,800 watts and if you pull more, it will just take it from the grid. No switching involved. Add a WattNode and it will sense the current at your breaker panel and dial down it's output when the cars stop charging so you don't exceed your NEM export limit. If you really ant to charge 2 cars, I would recommend 2 units, with one car charger on each, just to make sure you don't exceed the internal 60 amp transfer switch limit. That makes it so the unit can pass through over 14,000 watts at 240 volt. If your storage battery runs low, it will just stop inverting and the grid pass through will keep going at up to 60 amps as well.

In a full power fail situation, the grid tie solar moved to the "Essential Loads" panel will be able to help charge the cars, or back feed and help the DC coupled solar charge the home storage battery.

Back to the assumption that you want to be able to fully charge 40 KWH's in one day, during a power failure. Even on a good sun day with 5.5 hours of sun, that would need almost 8 KW of solar panel if you don't leave any power left for the house. That is doable, and falls inline with the numbers you gave in the original post. So it just leaves the big elephant in the room. What do you need for the battery bank?

You don't want to drag you home storage batteries below about 30% in daily use. Even on LFP that is pushing them a bit. So figure you will need about 60 to 80 KWH's of battery. Assuming 16S LFP packs, that is up to 1,500 amp hours. That is a lot of battery. More than 4 times what I have now. That will give you a little overhead to run some house loads, and if the cars are not pulled down as much you will have more reserve. Have you checked how much you actually do use? This is possible.

If you do produce excess power and your batteries are full, the existing AC coupled solar can sell to the grid through the XW-Pro, and the XW-Pro can even sell from the DC coupled solar as well. And you can set the sell limit, so it will curtail the DC solar output as needed after the batteries are full and you top out the NEM limit. And when you go off grid from a power failure, it is also able to frequency shift and curtail the AC coupled solar if it is exceeding the charge rate or if the batteries are full. I hope to do an off grid charge test on my system soon. I want to see it grid form and control my Enphase micro inverters and see if it works as smooth as they claim.

I am an end user who bought the system, and I obviously don't any compensation here. The build quality and robust nature of the XW-Pro is rock solid. The software just has a few small holes they need to work on. They have had 2 firmware updates in just 5 months, so they are working on it.

A Skybox is a simpler all in one and it does seem to do all AC coupling a little nicer for now than the Schneider setup. For my smallish system, the 5,000 watts would probably have been enough, and in hindsight, I might have been better off out of the box with it. But the separate component nature of the Schneider does have some advantages also. If I need to expand my system, it is very flexible and programmable to handle just about anything. My biggest software gripe is getting it to cut back to grid charging, but with adding DC solar, that is not really a concern for your setup.

 

[apachexmd]

That is one heck of a post GXMNow! Lots of great first hand information and lots to think about on my end.

What is the capacity of your electric cars, and how far do you run them down in a day?

I have a Chevy Spark EV and a Model 3. So 19kwh and 75kwh respectively. Weekdays I use maybe 8kwh just driving the Spark. The model 3 is strictly weekend duty, and then I probably use maybe 20ish kwh. Let's assume 14kwh per day on average just for cars. I almost never charge both cars in one night.

Back to the assumption that you want to be able to fully charge 40 KWH's in one day, during a power failure. Even on a good sun day with 5.5 hours of sun, that would need almost 8 KW of solar panel if you don't leave any power left for the house. That is doable, and falls inline with the numbers you gave in the original post. So it just leaves the big elephant in the room. What do you need for the battery bank?

You don't want to drag you home storage batteries below about 30% in daily use. Even on LFP that is pushing them a bit. So figure you will need about 60 to 80 KWH's of battery. Assuming 16S LFP packs, that is up to 1,500 amp hours. That is a lot of battery. More than 4 times what I have now.

Assuming 14ish kwh of EV charging per night with the 30% buffer, that puts me at 20kwh of battery just for EVs.

Have you checked how much you actually do use? This is possible.

This is something I still need to do. I will read my meter this week and next and try to get a daily average. With Covid and family working and schooling from home, the numbers are skewed a bit though.

I am an end user who bought the system, and I obviously don't any compensation here. The build quality and robust nature of the XW-Pro is rock solid. The software just has a few small holes they need to work on. They have had 2 firmware updates in just 5 months, so they are working on it.

It is good to know firmware updates are frequent.

A Skybox is a simpler all in one and it does seem to do all AC coupling a little nicer for now than the Schneider setup. For my smallish system, the 5,000 watts would probably have been enough, and in hindsight, I might have been better off out of the box with it. But the separate component nature of the Schneider does have some advantages also. If I need to expand my system, it is very flexible and programmable to handle just about anything. My biggest software gripe is getting it to cut back to grid charging, but with adding DC solar, that is not really a concern for your setup.

Expandability is a bit of a concern for me, since AC coupling with two Skyboxes isn't possible right now. Maybe it will be enabled in the future.

But I also gotta be realistic in my future power needs. I already drive all electric. I will never go to an electric range/oven. So overall I think my future power needs have leveled off.

Initial cost with a Conext XW Pro would be about $1000 to $1500 more than the Skybox. But it does offer a larger inverter capacity and expandability.

What percentage of your house loads are on your critical loads panel?

 

[Ampster]

I think I am in a similar situation where you once were, with similar goals.

I am on NEM 2.0 with those Non Bypassable Charges. Last year i got a big refund from Sonoma Clean Power which covered my minumums and my NBCs. SCP is reducing that but still paying more for excess and charging less for consumption. Perhaps you are also in one of the Bay Area CCAs?

I've dug up my signed copy of the NEM agreement and I can't find where it limits solar production to a certain number of KW. Where did you find the additional 1KW number?

They reference your inverter which is how they limit your production. I have 5.7 kW of panels on mine and that was not a problem. I will look at my NEM agreement and try to find the 1kW additional clause.

With the skybox are you able to customize battery charging voltages? Let's say I want to top off lithium ion cells to 4.1v instead of 4.2v per cell, can I do that?

Were you able to get your BMS talking to the Skybox via canbus? Batteries/BMS's is another thing that I think I need to do more research on.

Yes, I am able to set voltages from 48 to 59 volts with similar flexibility at the bottom. Right now with my new LFP pack I am going to only 3.42 per cell or 54.8 for the pack. Are you considering a LFP or NMC pack? It makes no difference to the Skybox. Until last month i was running a NMC pack of Nissan Leaf modules.
I have not yet figured out how to get my Orion BMS to talk over the CANBUS to my Skybox but that is not an issue. I do have a contactor that will cut out the pack if somehow the Skybox misses an event. So far that has not happened.

 

[GXMnow]

I have not moved over my main loads yet. Also due to Covid, I have 3 PC running full time with my son doing "distance learning" and myself working from home, so I am reluctant to shut down my main panel just yet. I had all my circuits labeled. I did not realize until I started pulling the wires in that the original solar install guys moved all of my breakers without marking anything. So I now have virtually no idea which circuits are which. So one of these weekends when I can shut down all the PC's and the hard drive based dish network box and WD TV unit, and external NAS hard drives, etc. Then I can start shutting off breakers and see what's what. I tried using a circuit tracer, you plug in one unit and find the tone at the breakers, but something else in my home is making a similar enough signal that the detector is being blinded and it shows 5 of my 14 breakers are the one, even without the sender module plugged in. So far, I know the garage wall outlets and air compressor, the A/C compressor, the ceiling lights in the kitchen, and that is about it. I want to get it traced before I have a real power failure and corrupt a few hard drives. At least my main PC and NAS are on a UPS, my son's PC is not. My work PC is a laptop and will live on battery a few hours. Most likely to lose data would be the WD TV and the Dish Network Hopper. The UPS I had on those croaked last year.

So for now, the XW is back feeding on it's grid input to my main AC panel. I have had it push as much as 15 amps at 240 (3,600 watts) so far. My feed in breaker is only 20 amps under my NEM 2.0 agreement. After I have my backup loads moved over, I will be able to have the inverter push it's full 28.3 amps divided between the "Essential Loads" panel, and the back feed to the "Main Panel". The Enphase solar is feeding the "EL" panel already. I have a 20 amp breaker for that, same as my original back feed that was in the "MP". Any of that power that is not used by the other "EL" panel loads will go back into the XW-Pro and help charge the batteries. If that power exceeds the charge rate power limit, or the battery bank is full, then any excess from there will go back to the "MP" from the grid input of the XW-Pro. If that back feed exceeds the power used by the rest of the "MP" loads, then it can still push out to the grid.

On the discharge side, it will similar. My "Peak Rate" time of use starts at 4 PM and my solar is still making some decent power. Right now I don't have a WattNode or any other monitor on the "MP" grid feed main. So I am manually adjusting my "Maximum Grid Sell Amps" value. This is actually smarter in the XW-Pro than I was expecting. It does measure the power on it's grid input (connected to the "MP") as well as the inverter output (Connected the the "EL" panel) So I had it set for 12 amps, but the solar was still making 13 amps. If I had loads in the "EL" panel, they would have been running off of the solar. But at the moment, I don't have a load there, so it was going through the XW and feeding the main panel at 13 amps, this is more than my sell setting, so the inverter just waited. If I was using 10 amps in the "EL" panel, then the other 3 amps would still be going back, but the inverter would power up and push another 9 amps to make the requested 12 amp back feed total. As the sun goes down, the inverter ramps up it's output to keep that 12 amps going back. Now, when I have real loads in the "EL" panel, the inverter will also raise it's output to keep feeding those as well as maintain the desired back feed current to the main "MP" panel. Of course, it is limited by the maximum battery current value and it's own 6,800 watt long term limit. While on grid, it will just top out and you will start pulling grid power. Adding the WattNode device, it adds the current sensors at the main breaker feed from the grid. The current software allows you to sett a power export limit. It will dynamically adjust it's output based on the power actually going to the grid, and not just to the main "MP" panel. The Skybox has inputs to add those current sensors as well, so this is not unique to the XW-Pro. In fact the current CT sensors alone for the SkyBox are certainly cheaper than the third party WatNode and current CT's, I will need to buy. But I am not in a big hurry for it at this point. I can legally back feed up to 16 amps at any given time, and export up to 900 KWH's in a month under my NEM so if I push a bit out when the A/C is off, I am not worried about it.

When I have to go off grid due to a power outage, I have the inverter set to be able to output it's full power to drive my loads, but I will want to go in and adjust the max charge current up. I am also going to try and automate that. I have suggested to Schneider to add a separate charge settings page when off grid. It just seems very dumb to use my safe slow charge rate and curtail the solar production when I could just be pushing it into the battery faster. If I am off grid, I want to top up the batteries quick, run on sun until it goes down, and have a full battery for the night. Since all of my solar is AC coupled, I have to be sure I have enough battery in the morning to still have my local grid to get the solar charging it again. With DC connected panels, that is less of a problem. The inverter will still shut down if you run the batteries too low, but once the sun is shining, it will start charging up, and the inverter will then come online, and the AC coupled will wake up and also help charge. With all AC coupled like me, if the battery goes too low, the inverter shuts down, and all of my solar goes off line. And it can't wake up on it's own. I have a few options around it. The best option is to make sure you don't run it down too far so it stays running all night, but we all know crap happens. Another option is to use a generator to bring the batteries up enough to start the inverter. It does even support auto generator start that can come on before it goes too low so it does not shut off. But my plan for now is to set the cutoff voltage a little higher, so I know the batteries actually do have enough power to form my grid in the morning. But it still does not self start. In the morning, I would have to connect in with a PC, but without power, so a battery laptop, and then set the low voltage cutoff down a volt or so to get the inverter back online and then the solar can reconnect to my local "grid" and the XW can use that power to charge again. In my Show and Tell thread, I have talked about the options I have with a PLC. This is not plug and play and I am learning to program as we go here. But I hope to have the PLC battery backed up and it will be able to send the commands to the XW to do all the mode changes. Maybe once I demonstrate it to Schneider they can add what I am doing into the Gateway. Yeah, not holding my breath.

 

[Ampster]

My feed in breaker is only 20 amps under my NEM 2.0 agreement

Can you clarify? If i recall my NEM agreements with SCE they referenced the inverter not the breaker. Both of those are over four years old and things may have changed.

 

[Ampster]

I have a Chevy Spark EV and a Model 3. So 19kwh and 75kwh respectively. Weekdays I use maybe 8kwh just driving the Spark. The model 3 is strictly weekend duty, and then I probably use maybe 20ish kwh. Let's assume 14kwh per day on average just for cars. I almost never charge both cars in one night.

I wanted to weigh in on the EV charging concept. My philosophy has evolved over time. I have had EVs since 2012. I currently have a 2016 Model X and a 2019 Model 3. Under NEM 1.0 I always thought that an EV was the perfect load shifting device. I traditionally had a net dollar credit but a net kWh deficit and the two offset each other. My consumption was as much as 2 mWhrs greater than my net production but the TOU rate differentials allowed me to build a dollar credit.

I have begun charging during the day to try to reduce my NBCs which are only a $0.2 adder to my rate. I haven't done the math either. However even with my new pack I am not sure I want to add the additional cycling of it by charging my EVs. It is also inefficient in terms of the DC to AC to DC conversions. The trick has been to charge the EVs at a rate that does not exceed my solar production. That is facilitated by the flexibility of my Clipper Creek EVSE which I can vary the current draw on the fly. This is still a work in progress but for now half of my charging is from solar, after my Skybox batteries are topped off by solar and half at Super Off Peak rates.
My True Up is in February and this is the time of the year that my production starts dropping and the big variable is my EV charging. I do have to put some numbers to this.

What percentage of your house loads are on your critical loads panel?

That is a good question and another work in progress. My main load panel and my critical loads panel are next to each other with wiring gutters top and bottom so I can move circuits easily. The only loads not on my critical loads panel are my 50 Amp EV charging circuit, my 30 Amp AC compressor, my 30 Amp electric dryer, and my 20 Amp dishwasher and garbage disposal plus some non essential receptacles.
I do have my FAU fan, all my lighting circuits (LEDs) most of my receptacles, a 30 Amp Heat Pump Water Heater and a 30 Amp EVSE recptacle on the critical loads panel. I am out of breaker spaces on my critical loads panel so that is another part that is a work in progress. I will have my electrician friend do a load analysis of I go to a larger panel. This latest heat wave has made me sensitive to the desire for some AC when the grid is down. I am glad I put the FAU fan in the loads panel because we use that to improve the air quality in the home. I might be able to get by with an efficient minisplit for the bedroom in the future. The point of all this is to build in flexibility which is important during these uncertain times.

 

[GXMnow]

I would have to dig out the paperwork to find the actual wording. But basically, I sized my original solar install to max out what I could do with my existing breaker panel. Being a 100 amp panel with a 100 amp main breaker, I was only allowed a 20 amp back feed breaker. That means 16 amps of solar can feed into my panel. I have 16 240 watt EnPhase iQ7 inverters that each can push 1 amp at clip. In spring, with cool sunny days, my 300 watt panels did run the whole array into clip at 16 amps, over 3,800 watts, for about 2 hours a day for almost a full week. So my limit may be written on the inverters, but it is also the limit of my breaker panel. The more load I can move to my "EL" panel, the more energy I can push and not violate that 16 amp limit into a 20 amp back feed breaker. If I spread the energy over more time, I then need to stay under my 900 KWH per month total energy export cap. I don't think that will be a problem. As I did top 31 KWH's of production for several days, it is possible I could hit 900 in a month, but there have always been a few days where the weather didn't hold up and of course, I am using a fair bit of the energy myself, and the NEM only sees what I don't use. They basically set the limit to what I could push out with my existing inverter(s) if I turned off all the loads in my home. So unless I go on a month long vacation, I will not exceed my monthly 900 KWH export without adding a ton of solar panels. So basically what I am stuck with is not exceeding the 16 amps going back to the main panel. For about 3 days, I had the inverter on it's own breaker and the solar still in the main panel, I had it pushing almost 20 amps with the two together, OOPS! I was using enough in the house that I know I still didn't send 16 amps out of the house, so for all the smart meter knows, I just turned off a bunch of loads. Now with the solar going through the XW, that can't happen, and if it did, the breaker would trip. In grid support inverting mode, the XW is very good and quick at self adjusting it's output that goes back to the grid input terminals. It also has another parameter where you tell it the size of the grid feed breaker. I did tell it 20 amps. If I have a lot of load in my "EL" panel it even knows to reduce charge current to not exceed the feed breaker. I would like to kick it up to a 30 amp to allow more power to flow to the "EL" panel when the grid is up, but still limit the back feed to my 20 amp limit, but by the letter of the 20% rule, it is not legal unless I lower my main breaker to a 90 amp. As with most things, you can't depend on someone entering the correct settings as someone can always do something stupid and the circuit breaker is there to prevent an unsafe condition if the XW inverter does try to pump 6,800 watts back to the grid while the solar is also pushing out it's 3,800 watts. In theory, that could mean as much as 44 amps going back to the main panel. I did run #8 awg wire. It barely fit in the 20 amp breaker lugs.

 

[Ampster]

No worries. It sounds like it was more of a code issue anyway. I don't think PGE or SCE care much about what goes on behind the meter except for the Inverter that is backfeeding them. I am taking that literally because my NEM agreement specifies my Solaredge inverter but that inverter is wired to the essential loads panel that flows through the Skybox. Since no one can identify the specific electrons moved by the Solaredge inverter I have not reported my Skybox installation to them nor do I intend to in the future.

 

[GXMnow]

I am a bit torn over my Schneider install. If I tell them I have it, I can go to the better ToU Prime rate which drops off peak from 25 to 15 cents per KWH, and only raises the peak from 40 to 42.