UL1791/Rule21 compliant hybrid inverters, 48V battery input

[zanydroid]

I'm doing some research into Rule 21 compliant hybrid inverters for a permitted on-grid installation in California (PG&E). Initial desire is to support solar panels, but as batteries for UL9540 systems get approved I'll be interested in slotting in storage.

Must have

• utility-interactive output with local consumption (demand shifting)
• 48V battery input
• ~5000kW inverter output
• reasonably easy to use MPPTs (voltage range, required safety features)
• Likely to be certified in a UL9540 system in the future
• can achieve demand shift without moving circuits to critical loads panel

Probably must-have

• 240V grid connection
• 120/240V critical loads output

Nice to have

• ideally capable of AC coupling with microinverters
• grid support on critical loads panel

Wondering what the conventional wisdom on the forum on this is, and whether I missed any inverters or important requirements to consider. I'm particularly interested in what the preferred models are, and what the brand expectations are around UL9540 compatibility in the future.

I'm also not sure what to look for to see if the hybrid inverter is able to trigger an ATS during a power outage and form a grid for the AC coupled panels.

So far, my research has yielded the following.

• SolArk 8K and greater - all requirements satisfied
• Solark 5K-1P - 120V only. I don't really want to put all my critical loads on 1 phase or be stuck with pushing imbalanced load to grid. That said, the distribution transformer would convert the imbalanced backfeed to 240V and satisfy demand shift. Not 100% clear whether this is CEC approved for grid connection. It's in the database but some seller websites say it's not approved.
• Schneider SW/XW + Charge controller - I looked through the XW documentation extensively. Not an all-in-one, needs a charge controller. Charge controller documentation was unclear on RSD and AFCI capability (RSD I can retrofit but AFCI I cannot). What is the difference between the SW and XW?
• Outback Radian + Charge controller. Similar architecture to Schneider, better documentation.

Overall it seems like SolArk has a decent number of partners certifying it in a UL9540 system

Things that seemed interesting at first but have some red flags:

• Outback SBX5048-120/240. The main objection I have with this is that it is designed for a larger solar installation than I want -- 250V-600V MPPT range, which requires over 8 panels in series (before bypass diodes kick in). I am not sure I have single roof planes that are big enough to support this
• EG4 8K hybrid (Magarevo). However, I don't see it on the CEC list and the manual looks pretty bad. Is it OK to file permits / interconnection for even though it's not on the CEC list but has the UL certifications?

 

[tacomaguy20]

I'm doing some research into Rule 21 compliant hybrid inverters for a permitted on-grid installation in California (PG&E). Initial desire is to support solar panels, but as batteries for UL9540 systems get approved I'll be interested in slotting in storage.

Must have

• utility-interactive output with local consumption (demand shifting)
• 48V battery input
• ~5000kW inverter output
• reasonably easy to use MPPTs (voltage range, required safety features)
• Likely to be certified in a UL9540 system in the future
• can achieve demand shift without moving circuits to critical loads panel

Probably must-have

• 240V grid connection
• 120/240V critical loads output

Nice to have

• ideally capable of AC coupling with microinverters
• grid support on critical loads panel

Wondering what the conventional wisdom on the forum on this is, and whether I missed any inverters or important requirements to consider. I'm particularly interested in what the preferred models are, and what the brand expectations are around UL9540 compatibility in the future.

I'm also not sure what to look for to see if the hybrid inverter is able to trigger an ATS during a power outage and form a grid for the AC coupled panels.

So far, my research has yielded the following.

• SolArk 8K and greater - all requirements satisfied
• Solark 5K-1P - 120V only. I don't really want to put all my critical loads on 1 phase or be stuck with pushing imbalanced load to grid. That said, the distribution transformer would convert the imbalanced backfeed to 240V and satisfy demand shift. Not 100% clear whether this is CEC approved for grid connection. It's in the database but some seller websites say it's not approved.
• Schneider SW/XW + Charge controller - I looked through the XW documentation extensively. Not an all-in-one, needs a charge controller. Charge controller documentation was unclear on RSD and AFCI capability (RSD I can retrofit but AFCI I cannot). What is the difference between the SW and XW?
• Outback Radian + Charge controller. Similar architecture to Schneider, better documentation.

Overall it seems like SolArk has a decent number of partners certifying it in a UL9540 system

Things that seemed interesting at first but have some red flags:

• Outback SBX5048-120/240. The main objection I have with this is that it is designed for a larger solar installation than I want -- 250V-600V MPPT range, which requires over 8 panels in series (before bypass diodes kick in). I am not sure I have single roof planes that are big enough to support this
• EG4 8K hybrid (Magarevo). However, I don't see it on the CEC list and the manual looks pretty bad. Is it OK to file permits / interconnection for even though it's not on the CEC list but has the UL certifications?

Did you ever decide on a system? I'm looking for something similar but a little larger. Looking at the SolArk or the new EG4 that's coming out.

 

[zanydroid]

Did you ever decide on a system? I'm looking for something similar but a little larger. Looking at the SolArk or the new EG4 that's coming out.

I honestly don’t remember this post and haven’t reread it in a while.

Given my next panels are going up with microinverters due to my site conditions these days I’m prioritizing AC couple performance over built in MPPTs. And battery charger/inverter + separate components.

New Chinese participants with advanced features that need some engineering or technician expertise? Give it 1 year to bake at least.

If I want to get something bleeding edge and actively developed, probably Rosie since it has a North America dev team.

 

[Hedges]

I would expect that SMA's European 8.0H Sunny Island would make it to the US eventually and have such features.

Rosie looks promising.
Schneider is being used by some forum members. Not doing everything he wants with only AC coupling (he has microinverters).

Coupling to microinverters has been problematic for in but not all systems.

48V battery ... HV battery from BYD is about twice the price of server rack 48V batteries. Works with Sunny Boy Storage, which has the features you want.

• EG4 8K hybrid (Magarevo). However, I don't see it on the CEC list and the manual looks pretty bad. Is it OK to file permits / interconnection for even though it's not on the CEC list but has the UL certifications?

I would think UL is sufficient to have permits signed off.
Not being on CEC list probably can't get PG&E's approval, so not authorized for backfeed. Maybe you could get away with it doing zero export.

 

[Ampster]

I'm also not sure what to look for to see if the hybrid inverter is able to trigger an ATS during a power outage and form a grid for the AC coupled panels.

The ATS will be implicit in any Rule 21 or UL1741SA/B inverters. It is more complicated with AC coupling, since that is not a requirement of any of the above standards. Having seen and used both the Outback and SolArk solutions. The key factors are the relationship of AC coupled GT solar to inverter capacity of the Hybrid (grid forming) inverter and the size of its battery pack. Also user input from working systems is also valuable input.

 

[zanydroid]

To do DC and AC combination at my house will require more advanced design skills than I have now. Maybe in 2 years if I’m still doing this hobby.

I have not found anything from EG4 on CEC list. Maybe if searched by the original manufacturer one can find it, but EG4 website last I checked makes it hard to figure that out. I did not check the 18K because of my aforementioned reservations about the platform maturity and quality of domestic engineering team and support.

 

[zanydroid]

The ATS will be implicit in any Rule 21 or UL1741SA/B inverters.

Yeah I understand that now, thanks. The first post is from 6 months ago and I didn’t go back and correct the mistakes in it after learning more about the area.

EDIT: some can trigger a remote contactor to serve as an ATS (Schneider XW) shared across multiple inverters. I assume some like SolArk will potentially flip their internal contactors in coordinated fashion if stacked, and wait to confirm disconnect on all inverters before activating.

 

[tacomaguy20]

To do DC and AC combination at my house will require more advanced design skills than I have now. Maybe in 2 years if I’m still doing this hobby.

I have not found anything from EG4 on CEC list. Maybe if searched by the original manufacturer one can find it, but EG4 website last I checked makes it hard to figure that out. I did not check the 18K because of my aforementioned reservations about the platform maturity and quality of domestic engineering team and support.

Yeah they are not on the list but supposedly soon? I'm planning out my project now but I'll likely be looking to install later in the year so that gives me a little time. I'm doing a new install and not looking to deal with microinverters so an all in one string inverter would be ideal for me. I was looking at Growatt Grid tied originally. Cheap inverter, meets certification requirements, seemingly easy to install but approved batteries are ridiculous priced and I'm stuck with high voltage and limited options. Sol-ark gives me low Voltage battery options (more providers added regularly), more flexibility for the future, but then I'm paying 4x for the inverter. EG4 looks promising because it's very similar to Sol-ark (spec wise anyways) and if they get their inverter + battery combo approved for grid tied (and work out any bugs), then the cost is a little more for the inverter, but a lot less for the batteries. So far that's the only grid tied +battery option that I've found that would be close to the price of an off grid system (only it's not approved yet and it might suck D'oh!) Maybe I'll forgo the battery, get my panels installed, buy a cheap grid tied inverter and then replace it when there are better inverter + battery combo options for grid tied.

 

[zanydroid]

Yeah they are not on the list but supposedly soon? I'm planning out my project now but I'll likely be looking to install later in the year so that gives me a little time. I'm doing a new install and not looking to deal with microinverters so an all in one string inverter would be ideal for me. I was looking at Growatt Grid tied originally. Cheap inverter, meets certification requirements, seemingly easy to install but approved batteries are ridiculous priced and I'm stuck with high voltage and limited options. Sol-ark gives me low Voltage battery options (more providers added regularly), more flexibility for the future, but then I'm paying 4x for the inverter. EG4 looks promising because it's very similar to Sol-ark (spec wise anyways) and if they get their inverter + battery combo approved for grid tied (and work out any bugs), then the cost is a little more for the inverter, but a lot less for the batteries. So far that's the only grid tied +battery option that I've found that would be close to the price of an off grid system (only it's not approved yet and it might suck D'oh!) Maybe I'll forgo the battery, get my panels installed, buy a cheap grid tied inverter and then replace it when there are better inverter + battery combo options for grid tied.

If you need UL9540 for your state then the cost delta between on-grid and off-grid is pretty low.

My general rule of thumb from now to EOY 2024 is that the system cost will be pretty consistent across all 9540 solutions today. +/- 15%. Cheaper or really cheap inverter? They'll make it up on the batteries. And vice versa. With some differences in edge cases, EG SolArk becomes cheaper if you add a high amount of storage.

Unless by off grid you mean, you pick and choose what code you follow.

Which is why I'm out of the market for a UL9540 solution until that late next year.

 

[tacomaguy20]

If you need UL9540 for your state then the cost delta between on-grid and off-grid is pretty low.

My general rule of thumb from now to EOY 2024 is that the system cost will be pretty consistent across all 9540 solutions today. +/- 15%. Cheaper or really cheap inverter? They'll make it up on the batteries. And vice versa. With some differences in edge cases, EG SolArk becomes cheaper if you add a high amount of storage.

Unless by off grid you mean, you pick and choose what code you follow.

Which is why I'm out of the market for a UL9540 solution until that late next year.

Well since I live where I live, I don't think I can use an off grid setup but I see a lot of posts on here saying I might be able to have an off grid system with a critical loads panel and just have it grid connected, instead of grid tied. As mentioned in the video below, a setup like the one Will is going over could be possible with a transfer switch (and run like a generator). As as far as grid tied though, it won't pass inspection. I still am not sure if I could run a setup similar to what Will has in this video below. However, if I could, it would cost me a fraction of the price for the inverters. $3000 for both instead of 7500 for one. And if I could use the Lifepower4 batteries, then I could have 10.25kw of batteries for another 2800. The whole setup for about $6000. That's dirt cheap for a solar system (minus the panels and misc. parts of course).

 

[zanydroid]

There’s two layers of jurisdiction here, POCO and local building department.

POCO often defers to local to do the inspections.

In California UL9540 is enforced by local inspectors.

You generally cannot run in parallel mode with a POCO without interconnect agreement. Here that is gated by sending in the stamped finaled permit to the POCO. Which means you are strongly required to have a highly certified ESS.

If you don’t parallel, there is probably less need for interconnection agreement. Which means there is no more gating on getting a finaled permits.

However then that gets into definition of what “attached generation facility” means, if the POCO or PUC asserts jurisdiction over that. Probably more than half of the people here that care to have looked into this, will want to say that an attached facility that is either completely air gapped or not AC coupled to grid doesn’t count (either legally, or even if the regulation or contract says it counts, morally it is not so).

 

[FilterGuy]

Well since I live where I live, I don't think I can use an off grid setup but I see a lot of posts on here saying I might be able to have an off grid system with a critical loads panel and just have it grid connected, instead of grid tied.

Each situation and each jurisdiction can be different, but a lot of what people say doesn't need to meet code actually does.

In most urban and sub-urban jurisdictions, any permanent wiring is supposed to have permits and the permitting authority is going to go all code on you. Even many rural areas that have no inspectors or inspection processes still have code requirements, it is just not enforced. (If a state has state-wide code requirements, the guy out in the rural area may not have inspectors, but the code still applies) This means that with a fully off-grid system with no connection to the grid, there are often still code requirements that are supposed to be met. However, many of the code requirements relating to grid interaction may not be required if there isn't a grid-interactive inverter. (I say 'may' not because I can easily imagine situations where broad blanket rules are applied even when they don't apply to the situation). So, even if you do it yourself and don't have a grid-interactive inverter, you may still have code requirements that are supposed to follow.

Where things may get less restrictive is when you are dealing with non-permanent wiring. As an example, If you build one of Wills Milk-Crate Solar generators, you are far less likely to run into building code requirements.

Note: In most situations, the code requirements (if enforced correctly), are not a bad thing. The code may be a PITA and co$t a lot, but the NEC puts them in place for good reasons.

 

[zanydroid]

but a lot of what people say doesn't need to meet code actually does.

To clarify, my comment above was partly around what de facto code enforcement is, and what checks there are.

In theory, if a jurisdiction has restrictions on all generation facilities and really cares to enforce it, they can use aerial photography of the sort used to get leads on tax cheats (IE, look for solar panels, vs look for expensive pools and additions on houses that aren’t on the tax rolls to be worth that much). I don’t think anybody does that in the U.S. even though aerial photography is now very cheap and I’m sure machine review to auto calculate the number of panels you have in a picture has high precision.

 

[FilterGuy]

To clarify, my comment above was partly around what de facto code enforcement is, and what checks there are.

In theory, if a jurisdiction has restrictions on all generation facilities and really cares to enforce it, they can use aerial photography of the sort used to get leads on tax cheats (IE, look for solar panels, vs look for expensive pools and additions on houses that aren’t on the tax rolls to be worth that much). I don’t think anybody does that in the U.S. even though aerial photography is now very cheap and I’m sure machine review to auto calculate the number of panels you have in a picture has high precision.

Shhhh!!! Don't give 'em any ideas

 

[zanydroid]

Shhhh!!! Don't give 'em any ideas

It’ll go through the same civic life cycle as traffic cameras :laugh: