Seeking Advice: Grid-separated EG4 12000XP using an interior load center

[No-one-&-Not-Important]

Note: NO affiliate links below; just highlighting which products I'm using.

*** IMPROVEMENTS MADE SINCE ORIGINAL POST BASED ON COMMENTS ***
Thanks @TM48 & @green-river @CJ Solar for the notes.

1. CRITICAL: Upgrade from 28kWh to 64kWh battery capacity to ensure you have enough current coming from batteries to power loads
2. Be conservative in how close you get to inverter peak (and surge). It's one way to wear them out quickly.
3. Use a combiner LC for both inverters to enable powering down the inverters one at a time for maintenance; requires loading and storing two configs for each inverter so one can be running even if other is down.
4. Balance strings better; 9-10 panels per string
5. Add batteries in parallel to BOTH inverters via busbar so they can be charged by both
6. 12000XP can't pull from battery and AC input simultaneously. So plan accordingly.

_______________________________________________________________

QUESTIONS​

1. Re: my config (below), would you please share warnings, comments or "gotchas" (e.g.: monitoring, batteries, FW, AHJ issues, etc...)?
2. Besides what's in the 12000XP spec (read it), has anyone had experience with the AC input function on the 12000XP and its limitations?
3. Any one have PoCo issues with 12000XP import only?
4. What happens when voltage exceeds the MPPT operating voltage range spec (385V) but is below the max of 480V?
5. Does anyone know what the 12000XP battery surge spec (couldn't find it in the spec sheet)?

Proposed system seems simple but threads I read (see below) indicate many issues pop up. So if you can think of anything I should be aware of, it would be very much appreciated. Thank you in advance.

_______________________________________

Location: San Jose, CA, PoCo: PGE ().
Profession: DIYer, Electrical Engineer + Product Manager (SW/HW) in hi-tech
Environment: Zero shading

SYSTEM & USAGE DESCRIPTION (EDITED GIVEN BELOW FEEDBACK)​

System​

• Inverter: 2x 12000XP
• Battery: 4 x 16kWh batt (DIY, All 4 connected to inverters)
• Solar PV: 14.4kW (Hyperion 400W x 36, 4 strings: 1 x 2.4kW + 3 x 4kW strings), Voc = 37.1V/panel up to 41.7V at -8°C/18°F.
• Generator: 2kW generator which can supply 1kW for 8 hr sustained, reviewed in detail here incl. engine wear, has clean sine wave output.

Loads: Max sustained/surge current : 100A/Surge=150A (4-ton AC compressor; likely to be replaced with heat pump)
Battery Draw: Current model implies max battery current/power: <61A (maximum of 7.3kW)

ONE PHASE INSTALL - TWO PHASE TO CONNECT GRID​

Phase 1: I will install inverters, batteries and solar PV panels. And connect to a NEW interior load center (LC). I will move all property circuits to interior LC from current main+meter LC (on the exterior). There will be no grid connection to interior LC or inverter. I will operate after City AHJ approval. I will use generator to supplement battery power when needed
Phase 2: Connect PoCo as AC input; PoCo will be generator backup

MAIN OPERATING MODE​

• Solar PV provide energy to non-battery LOADS --> store excess solar PV energy in batteries
• When batteries at 100%, DO NOT EXPORT to PoCo (ZERO EXPORT)
• When no Solar PV energy, use batteries for non-battery LOADS until battery SOC is 20% --> Use generator to charge batteries
• [Phase 2] Draw energy from PoCo to supply LOADS as a backup to the generator

Why this setup and a phased approach?
To bypass PoCo rules & procedures legally, I'll install a new interior load center (LC) in the garage (~3ft from exterior LC) & move all circuit breakers from exterior to interior LC. PoCo feed remains connected to old LC (with no circuits). By designing to minimize grid dependence, I'll need <100 kWh/year from a generator (over 46 hour period across 7 days, occurs when battery SOC is 20%; calculated using a "1h granularity" model, 24hrs x 365days PVWatts data, weather data from past 10 years to estimate hourly granularity gen vs property consumption data from the past THREE (3) years). I'll have to refill the generator ~7x (part of maintenance anyway). Is it cost effective? $4/gallon for 8kWh ~equivalent to PoCo $0.50/kWh's fees.

Read the following threads
1. https://diysolarforum.com/threads/12000xp-off-grid-setup-overloads.95717/
2. https://diysolarforum.com/threads/eg4-12000xp-off-grid-option.92732/

 

[No-one-&-Not-Important]

Adding others (experience with 12000XP).
Hope I'm not bothering you with this request. Thank you in advance!

@CJ Solar​

@confusedengineer​

@killercarver​

@zanydroid​

 

[TM48]

Two 12000xps will draw more than 60 amps of battery. You might want to re-check the specs. Plus IMO you're very light on battery capacity for two 12000xps. Also I'd configure the panels as 4 strings of 9. You might think of a soft start on your A/C depending on the size. If you have a 4 ton or greater your lock rotor amperage will be north of 100 amps. I don't recommend overloading these inverters.

 

[No-one-&-Not-Important]

@TM48 - Thank you very much for checking and providing your suggestions...

Also I'd configure the panels as 4 strings of 9.

I'd like that too; I connected the panels (Hyperion 400W Bifacial) in the above config bc one is facing facing S (6), 2 face W & 1 faces E). I think your suggestion of 9 panels is to avoid maxing out V_oc in the winter; is that correct? Our coldest weather is ~2C/35F. Since the panels have a -0.27%/C voltage coefficient, I converted this to V_oc of 37.1*1.11 = 41.2V and so 9*41.2 = 371V which is within the operating range. Does that sound right?

You might think of a soft start on your A/C depending on the size. If you have a 4 ton or greater your lock rotor amperage will be north of 100 amps. I don't recommend overloading these inverters.

Thanks for the advice; I agree 100%. BTW, have you had a bad experience with the 12000XP with surge currents? Property came with a 4-ton model (R22 based, YORK TCGD48-S21S2HA; 20 years old now; have had zero issues with it); surges to 86A, runs at 23A). So yes, I'll either have to add a soft start or replace with a more efficient heat pump (cooling/heating). The only thing is that the ROI on the heat pump just doesn't make sense now that I'll have that much solar electric production (esp. in the summer). And so I'll have to figure out if the unit I have can accommodate a soft start without destroying it).

Two 12000xps will draw more than 60 amps of battery

I think you mean the 2x12000XPs can draw more than 60A, is that correct? I shared that based on my usage pattern over any one hour period, I'd only ever need to draw 60A@120V (7.1kWh) so I believe the batteries which offer up to 250A/50V can deliver this and the 12000XP can handle this so I think you're aligned but just checking in case I missed something.

Plus IMO you're very light on battery capacity for two 12000xps.

Yes, I'd definitely like more. After modeling it, it turns out the batteries at current pricing will cost more than I'd save over a 10 year period. 5kWh of batteries would need to be <$900 for it to be worth it. If you're interested in how that model looks, you can have a look.


Again, thank you so much for your input... Much appreciated.

 

[TM48]

Yes a 9 panel arrangement will be safe in your environment.

No I've had no surge problems with my 2 6000xps. Having worked with power electronics for years I'm conservative in overall system design. If you want a trouble free system operate it well within it's specifications. There is a difference between a surge and an overload. If the inverter is switching to grid that's an overload. Recently there was a thread where a 18kpv was operated with a 5 ton a/c with no soft start. It lasted 6 months.

A single Powerpro battery is rated to supply up to 200 amps so it does not meet the recommended 250 amps. The inverter cannot deliver it's rated output power without adequate battery power. It is common to under estimate system usage. Empirical data on usage will open your eyes. Also you're not factoring in inverter/battery efficiency losses.

Yes batteries are expensive. But they are the heart of any off grid system. It's difficult to justify an off grid system on economics alone so if your only reason is to save money you might want to reconsider. I place high value on the independence it affords one. My project started as a "minimum services" system for the aftermath of a hurricane. After watching it operate it was expanded to include the central air and other less important circuits. Mission creep is really common. Now it is a hobby.

 

[CJ Solar]

Context

Panel Setup: My current property electrical load center (LC; aka circuit breaker panel) is an exterior LC integrated entirely as one "whole" with the PoCo meter (an asinine design if I've ever seen one). By moving all my circuits to a new LC, I'll in effect have no physical path from the new LC to PoCo's grid (therefore only need one AHJ (SJ city) approval). The 12000XP will be connected to the new LC. Property would remain grid connected via the old LC (if for whatever reason in the future I needed to reconfigure the system or the next owner doesn't like this setup).

Am I sure I won't be left out in the "cold"? Using a monte carlo simulation of a "1h granularity" over 365d (PVWatts data; per hour gen vs consumption) from the past THREE (3) years of property usage data, I determined the 95th percentile (worst case) draw from external source will be <400kWh (spread over 445 hours & 21 days throughout the year). Generator (Cost: $350, runs at 61db (tested)) has operating costs of 1gallon/8kWh. At $4/gallon this is equivalent to PoCo $0.50/kWh. PGE's energy is 30% renewable & this matters to me.

Read the following threads
1. https://diysolarforum.com/threads/12000xp-off-grid-setup-overloads.95717/
2. https://diysolarforum.com/threads/eg4-12000xp-off-grid-option.92732/

Adding others (experience with 12000XP).
Hope I'm not bothering you with this request.

@CJ Solar​

@confusedengineer​

@killercarver​

@zanydroid​

I will start by saying I am not an expert and there is a ton of great people here who really know what they are doing. I just received my first order of solar equipment yesterday. I did go with one 12000xp, I will add a second next year. Batteries were a priority with this purchase, 4 eg4 indoor wall mount and 2 Ruixu wall mount batteries. 30 530w panels. 30 more next year for the second inverter. My solar shed has really consumed my time so far. I am still learning and researching every day something I did not plan for completely (grounding and SPD)

 

[No-one-&-Not-Important]

A single Powerpro battery is rated to supply up to 200 amps so it does not meet the recommended 250 amps. The inverter cannot deliver it's rated output power without adequate battery power. It is common to under estimate system usage. Empirical data on usage will open your eyes. Also you're not factoring in inverter/battery efficiency losses.

Oh... I think I understand your point now. Yes, the battery delivery needs to match the required input for the inverter to work well. I had not factored this in. Thanks!

No I've had no surge problems with my 2 6000xps. Having worked with power electronics for years I'm conservative in overall system design. If you want a trouble free system operate it well within it's specifications. There is a difference between a surge and an overload. If the inverter is switching to grid that's an overload. Recently there was a thread where a 18kpv was operated with a 5 ton a/c with no soft start. It lasted 6 months.

I want to program the 12000XPs so the grid charges batteries only, not to support loads. There is a way to do this on the 12000XPs, no?

Independence does play a factor; but I'm in a city; if "hell" breaks loose & I am the one with power when most neighbors don't have any, I am not sure I can fend off as many people who have shed the very thin veil of civility we pretend to maintain with one another. Having said that, operating well within specs really does matter to me. I am an electrical engineer and my cars last 15+ years because I change oil every 5k (even if synthetic), I warm the car up for 2 mins before I start driving to keep the transmission clean, I recharge my auto batteries myself every 3 months, etc...

 

[green-river]

14.4kW PV (400Wx36, 3 strings: 1 x 2.4kW + 3 x 4kW strings), Voc = 37.1V/panel

I think there might be a typo here. Did you mean "4 strings" instead of "3 strings"?

Considering San Jose's record low temperature of 18ºF, the Hyperion panels with a VoC of 37.07V would peak at about 41.36V.

With this in mind, a string of 11 panels would hit around 455V, which is a bit too close to the 12000XP's max input of 480V.

To be safe, I'd suggest sticking with no more than 10 panels in series, giving you a max voltage closer to 410V. Even 9 panels per string would be fine, but definitely don't exceed 10 to keep your equipment safe and sound!

 

[green-river]

TL;DR:
2 batteries is a fine start. Hell, they're expensive, I get it. But. I'd recommend planning for future expansion by setting up physical space and wiring for a total of 4 batteries, 2 per inverter, so when you're ready to expand, it's just a matter of installation.

Given your plan for a max battery output of 7kW, starting with one battery per 12000XP inverter will work. EG4 recommends setting each battery to discharge at 7.6kW. But keep in mind that, at night, you won't be able to pull the full 12kW from the inverter. Since the battery is the bottleneck at 7.6kW.

You can certainly start with this setup now. Solar is kind of addictive; you might find yourself wanting to electrify more things around your home over time. Your battery system can grow with your needs or as you experience "mission creep." For instance, whenever that 20-year-old A/C bites the dust, replacing it with a heat pump, which would increase your night-time kWh storage needs for heating in the winter.

According to your spreadsheet, you’re already at that point though, in the summer on the hot July and August nights, where you run out of battery before the sun comes up and need to pull from the grid. So additional batteries could be useful in both peak winter and peak summer.

Also, as a side note, what size is the house? Does it really need 48,000 BTU (4 tons) of cooling capacity? Just double checking that the existing unit isn't oversized.

 

[green-river]

Consider adding a heat pump clothes dryer to your setup. From LG, GE, or Samsung.

Here’s why:
Imagine a hot September evening with the air conditioning running (5.5 kW), you’re cooking dinner (2–4 kW), and starting a load of laundry (6.25 kW). Your total power demand hits 14.5 kW/61A—already exceeding the maximum you said you’d ever pull from batteries.

Add just a few more appliances, like a microwave, fridge or freezer cycling, and you’re even more over the limit.

A heat pump dryer, which typically draws only 0.4–0.9 kW, can significantly lower your loads and provide more breathing room for your system during high-demand times.

 

[green-river]

Have you decided between taps or an inverter combiner panel to merge the outputs of the two 12000XPs into one conductor for the new LC?

For ease of service, I'd recommend a combiner panel. This way, you can isolate one of the two inverters by flipping a breaker, making maintenance much simpler if one needs to go down for servicing. Then, use 4/0 Aluminum cable to run from the combiner panel to the new load center in the garage.

To future-proof your system, I'd suggest thinking of the wiring in 100A not just 50A. And using 1 AWG XHHW-2 Aluminum Cable, which can handle 100 Amps. So you're ready to use the grid bypass mode to utilize the 100A bypass feature of each inverter.

Since you're in San Jose with a pretty stable electrical grid and a house already on the grid. It may be easier to use the grid for backup when more energy is needed on stormy weeks instead of that generator.

 

[green-river]

What you currently have outside your house, which you referred to as an "asinine design," is known as a combo meter-main panel. You could replace this with a single 200A disconnect that feeds into the inverter's grid input. This external disconnect is now required by NEC code since your home was originally built.

Planning for the future, including for future owners, is always wise. Here's what you'd need:

1. A 200A external meter/disconnect combo (Eaton CMBEB200BTS or CMBEB200BTF)
2. 4/0 AL service entrance cable
3. An inverter combiner panel with two 100A breakers

A good replacement for your existing meter/panel combo would be: an Eaton "Meter Center" with "No Distribution", which simply means it has one 200A disconnect without any additional breakers. Depending on whether you need surface mount or flush mount, the product numbers are CMBEB200BTS or CMBEB200BTF. And these models are EUSERC approved for use with PG&E.

From there, run 4/0 AL service cable from this new external disconnect to an inverter combiner panel, which will distribute 100A to each 12000XP's grid input.

 

[green-river]

Does the AC input function work on the 12000XP; anyone try it)? Anyone have PoCo issues with 12000XP import only?

The 12000XP just appears like a load to the PoCo. To PG&E it'll just look like a big load—like charging an EV. They can't really tell anything.

There are a few videos of people pushing the 6000XP to 99%, 100%, 101% and waiting for it to flip to grid. The grid bypass will happen automatically by the time it gets to about 110%. Assuming the 12000XP works the same way, it's just too new to have this type of content yet on YouTube.

Here is one such video, if you search around you can find a few more:

 

[No-one-&-Not-Important]

@green-river Thanks a lot; a lot of great input to consider (and I respond to everything below).

I want to clarify my desired operating mode.

MAIN OPERATING MODE
When solar PV can provide enough energy to non-battery LOADS, store any excess energy in batteries. If excess solar PV energy is available & batteries at 100%, DO NOT EXPORT anything (ZERO EXPORT) to PoCo. When solar PV is insufficient for non-battery LOADS, use batteries to support non-battery LOADS until SOC is 20%. When battery SOC dips below 20%, use generator to charge batteries. When solar PV is not present and batteries are insufficient to support non-battery LOADS, draw energy from PoCo while battery is supplying power at the same time. Note: Re: Grid/PoCo; This only happens when Grid/PoCo is finally connected to 12000XP; which happens after initial install and approval from city AHJ). When Grid/PoCo are eventually connected for import, it requires that batteries & AC input can be used at the same time to support non-battery LOADS.

To achieve the above, i.e.: not have a Grid/PoCo connection for the first 8-12 months, I'm sizing PV + batteries sufficiently & adding a generator. i.e.: 14kW + 28kWh + generator. This allows me to keep operating as I would normally until PGE decides it has enough time to send someone to approve the connection to 12000XP for import only. In the mean time, I can generate energy.

Outstanding questions
1. Can 12000XP pull from AC Input (Grid or Generator) & Battery at the same time whether supplying energy from PV or not?
2. How does a non-listed 14.3kWh battery (equivalent features to EG4/others) communicate properly with the 12000XP (using the lead-acid setting) to inform inverter if it is fully charged?


______________________________________________________________

I think there might be a typo here. Did you mean "4 strings" instead of "3 strings"?

Yup. Made an error. Corrected the post. Thanks.

To be safe, I'd suggest sticking with no more than 10 panels in series, giving you a max voltage closer to 410V. Even 9 panels per string would be fine, but definitely don't exceed 10 to keep your equipment safe and sound!

Noted; BTW, per 12000XP data sheet, the "MPPT Operating Voltage range" is 120-385V. Shouldn't that be taken into account? It just feels like it basically will simply clamp to a max current above 385V, even if I'm at 420V (10panels x 41.7V).

Comments?

2 batteries is a fine start. Hell, they're expensive, I get it. But. I'd recommend planning for future expansion by setting up physical space and wiring for a total of 4 batteries, 2 per inverter, so when you're ready to expand, it's just a matter of installation.

I agree more is better. Setup includes space for more and that is the plan; like you said "mission creep". All too familiar in other domains.

What do you think about building a 14.3kWh battery (280Ah 51.2V (16*3.2V EVE 280Ah Grade A (QR Code checked) cells) with a Daly 16S BMS, aluminum enclosures, fire suppression, surge protection, rapid shutdown & wireless). It'll cost ~1.5hrs/battery in time. Pros: Half the price + can make changes if needed (hopefully rarely). Cons: Not sure how it'll communicate with 12000XP. I checked with EG4 tech support. If I use the "lead-acid" battery setting (which a stand in for "any battery"), I can config the battery settings for charge/discharge but it's unclear how the BMS sends signals back to the 12000XP to let it know not to charge any more so this is a big QUESTION mark... and probably the PRIMARY reason I wouldn't do this.

Re: DIY battery - If other posts you're aware of have addressed this, can you point out. I haven't found them.

Comments?

Also, as a side note, what size is the house? Does it really need 48,000 BTU (4 tons) of cooling capacity? Just double checking that the existing unit isn't oversized.

Yes, it's oversized (I inherited this when I bought the home). I found all of this out when I realized my ductwork had leaks).

Also, it's likely I'll replace the 20+ year-old AC compressor with a heat pump (since it's likely to "die" soon), and calcs (CFM, duct sizing (too small for size, etc...) revealed the 4-ton system was oversized & underperforming. Yes, I'd have to adjust the battery consumption and sizing at night since heat pump would work continuously... Great point!

For ease of service, I'd recommend a combiner panel. This way, you can isolate one of the two inverters by flipping a breaker, making maintenance much simpler if one needs to go down for servicing. Then, use 4/0 Aluminum cable to run from the combiner panel to the new load center in the garage.

Plan was a to use my interior LC (i.e.: then I can shut off the breaker for the specific inverter for maintenance/isolation). If that's not right, can you share why? Any other Comments?

To future-proof your system, I'd suggest thinking of the wiring in 100A not just 50A. And using 1 AWG XHHW-2 Aluminum Cable, which can handle 100 Amps. So you're ready to use the grid bypass mode to utilize the 100A bypass feature of each inverter.

Thanks for bringing this up. I had that in mind. Short distance. Not much of a cost delta. Thanks again.

What you currently have outside your house, which you referred to as an "asinine design," is known as a combo meter-main panel. You could replace this with a single 200A disconnect that feeds into the inverter's grid input. This external disconnect is now required by NEC code since your home was originally built.

Planning for the future, including for future owners, is always wise. Here's what you'd need:

1. A 200A external meter/disconnect combo (Eaton CMBEB200BTS or CMBEB200BTF)
2. 4/0 AL service entrance cable
3. An inverter combiner panel with two 100A breakers

A good replacement for your existing meter/panel combo would be: an Eaton "Meter Center" with "No Distribution", which simply means it has one 200A disconnect without any additional breakers. Depending on whether you need surface mount or flush mount, the product numbers are CMBEB200BTS or CMBEB200BTF. And these models are EUSERC approved for use with PG&E.

From there, run 4/0 AL service cable from this new external disconnect to an inverter combiner panel, which will distribute 100A to each 12000XP's grid input.

First, I want to state I don't want to touch anything to do with PGE. PGE has been difficult to deal with on the best of days & simply impossible on others. I cannot express how painful the idea of PGE is. The ridiculous bills ($700-$800/month, 4 years ago we used 20% more kWh and our highest bill in the year was $312), the 5x/year pricing increases for the past few years, the inflexibility, the "planned" power shutdowns. PGE might as well be an extortionist with a license form the state. Have I expressed it well enough? So how can I replace the combo main+meter without talking to PGE? I don't see how this is going to happen. If I missed something, let me know.

OTOH, by using a separate LC (as stated in my initial post) to isolate circuits entirely from PG&E, I effectively leave the utility connection unused but intact on the exterior LC (which has the combo meter). The different interior LC provides future upgradability and I can use my system and apply for a permit and PGE can take as long as they want. If PGE gets easier to deal with, I'll make changes. If not, the future owners can decide if they want to deal with PGE. Right now, I eliminate dependence on the utility connection but I keep it available for emergencies or future use. This also avoids the need for major rewiring or upgrading the meter-main combo. Until PGE decides to finally approve the connection and perform the inspection to the 12000XP for import, I still control whether to use PG&E simply by switching the main disconnect on/off without reconfiguring circuits or panels.

The 12000XP just appears like a load to the PoCo. To PG&E it'll just look like a big load—like charging an EV. They can't really tell anything.

There are a few videos of people pushing the 6000XP to 99%, 100%, 101% and waiting for it to flip to grid. The grid bypass will happen automatically by the time it gets to about 110%. Assuming the 12000XP works the same way, it's just too new to have this type of content yet on YouTube.

Here is one such video, if you search around you can find a few more:

Isn't the whole point to "supplement" from the grid if connected, not to "flip" to it. Did you mean "supplement"? Also, I want to be clear, I want to ONLY ever draw from the grid if my battery & PV panels can't supply to the loads. In my setup, the grid is never going to charge batteries, only for loads. NO EXPORT ever to PGE until there is an incentive to do so...

Again, thank you for everything. Cheers!

 

[green-river]

I do not understand the 100A AC bypass function. Since AC output is limited to 50A. How can the 100A bypass be used as an output?

I don't think I understand the 100A bypass feature. How would I use this? I see the AC Output limited to 50A, so how can I use this 100A as an output to the LC? I inferred from your statement that the 100A bypass can somehow be used as an output. How is that?

It's two different things:

• The 12000XP can GENERATE 50A of AC power with its transformers, capacitors, and transistors
• The 12000XP can DELIVER 100A of AC power through its relay, conductors, and terminals

The cost of a 100A (24kW) inverter is a lot. The cost of short little wires and terminals that support 100A (24kW) is a little. Meaning, as a convenience, they put in larger components in the relay and terminals. Just to passthrough a little more current when you flip to grid. They could have just used smaller wires and ports to match the 50A, but they did ya a solid and put in a bit more metal.

If, in many years and PG&E willing, you get the grid connected to the back of these 12000XPs, you'll want to be able to pass through up to 100A from the grid to the loads. So just use 100A conductors now coming out of the LOAD port so you don't have to redo it later.

 

[green-river]

Isn't the whole point to "supplement" from the grid if connected, not to "flip" to it. Did you mean "supplement"? Also, I want to be clear, I want to ONLY ever draw from the grid if my battery & PV panels can't supply to the loads. In my setup, the grid is never going to charge batteries, only for loads. NO EXPORT ever to PGE until there is an incentive to do so...

No. The 12000XP is an offgrid inverter and therefore it has no "grid interactivity" functionality. This means:

• There is no supplement capability
• There is no export capability

This is on page 18 of the manual (7.3 AC CONNECTIONS):
"The loads output can receive AC current directly from the AC input or current inverted from PV and battery."

So when it switches to "bypass mode", it literally flips a relay and takes itself out of the equation. And just passes through power right from the GRID port to the LOAD port. Older generations of off-grid inverters didn’t include a bypass—it’s a convenience feature added in newer models. It’s a relatively very small additional cost for a few components, like a relay and an extra terminal, but it offers big benefits in flexibility and capabilities.

If your goal is to blend power (aka "supplement"), you’ll need a grid-interactive inverter instead (EG: 18kPV, 12kPV, FLEXBOSS21), even if you’re supplementing with zero export.

 

[No-one-&-Not-Important]

No. The 12000XP is an offgrid inverter and therefore it has no "grid interactivity" functionality. This means:

• There is no supplement capability
• There is no export capability

This is on page 18 of the manual (7.3 AC CONNECTIONS):
"The loads output can receive AC current directly from the AC input or current inverted from PV and battery."

So when it switches to "bypass mode", it literally flips a relay and takes itself out of the equation. And just passes through power right from the GRID port to the LOAD port. Older generations of off-grid inverters didn’t include a bypass—it’s a convenience feature added in newer models. It’s a relatively very small additional cost for a few components, like a relay and an extra terminal, but it offers big benefits in flexibility and capabilities.

If your goal is to blend power (aka "supplement"), you’ll need a grid-interactive inverter instead (EG: 18kPV, 12kPV, FLEXBOSS21), even if you’re supplementing with zero export.

Thanks. The pain... The term "or" is misleading; sentence requires a "but not both at the same time" or some equivalent phrasing. I'm finding these specs leave some to be desired.

 

[No-one-&-Not-Important]

It's two different things:

• The 12000XP can GENERATE 50A of AC power with its transformers, capacitors, and transistors
• The 12000XP can DELIVER 100A of AC power through its relay, conductors, and terminals

The cost of a 100A (24kW) inverter is a lot. The cost of short little wires and terminals that support 100A (24kW) is a little. Meaning, as a convenience, they put in larger components in the relay and terminals. Just to passthrough a little more current when you flip to grid. They could have just used smaller wires and ports to match the 50A, but they did ya a solid and put in a bit more metal.

If, in many years and PG&E willing, you get the grid connected to the back of these 12000XPs, you'll want to be able to pass through up to 100A from the grid to the loads. So just use 100A conductors now coming out of the LOAD port so you don't have to redo it later.

Thanks. Yes, I finally figured what that "bypass" term meant. Still, that was a very solid explanation. Helped cement what I was thinking.
BTW - Re: your comment about building a 100A inverter costing a lot.

I'd argue (experience from 10+ years in the semiconductor manufacturing & product industry) is that it does not cost a lot more at all.

• Wiring: The wiring is local to the inverter so the incremental cost is not wiring.
• Boards and Components: Someone might argue it's the boards and ICs e.g.: MOSFETs and without going into the minutiae of MOSFET design and manufacturing costs, I'll just point to a comparison of the FB21's and 18kPV cost delta. The FB21 only misses on the GEN input vs the 18kPV. It can support 66A AC output and it's $800 cheaper (now) --> Conclusion: Building a 100A (24kW) inverter is NOT much more expensive at all. The board and ICs are in high volume production out of China (ASMC, CR Micro, Hua Hong Group, Sanan IC), Taiwan (TSMC, though it's a small part of their business), S. Korea (Samsung), Singapore (UMC, Global Foundries)). MOSFETs and boards cost in the $10s of dollars more.
• Certification: Someone else might say it's the certification. And I'd repeat what I said earlier above in my response to @AntronX.= here.

The pricing delta we see for 100A vs 50A inverters is "value extraction" driven, not cost-based. It's opportunistic and predatory and a big part of it is that distribution and sales (the margin stack) takes 20-30% of sales, and sales can't be low value, otherwise how do you incentivize the sales people to make a sale (those you call on the phone at the various solar sales companies). Given the prevailing rate for DIY versus "Done for You" is ~$900/hr (as per my quote earlier), I'd say I can breakdown the BOM for how 100A/24kW inverters can be purchased for ~$1500 with the OEM still making a 50% GM if they had a direct sales channel, and used independent consultants to help drive the ecosystem to choose between the various makers.

When you consider what DIY solar forum is, the non-OEM experts here are just the "unpaid" independent consultants. The ecosystem has a lot of room to grow and improve; For now, it's still "early days".

 

[No-one-&-Not-Important]

I will start by saying I am not an expert and there is a ton of great people here who really know what they are doing. I just received my first order of solar equipment yesterday. I did go with one 12000xp, I will add a second next year. Batteries were a priority with this purchase, 4 eg4 indoor wall mount and 2 Ruixu wall mount batteries. 30 530w panels. 30 more next year for the second inverter. My solar shed has really consumed my time so far. I am still learning and researching every day something I did not plan for completely (grounding and SPD)

Yes, very important. Grounding & SPD is on my list of to do's. Since we're are in very low lightning strike zone (as per this map (FEMA Lightning strike)), it's not my first priority right now but don't want to lose $1000s without investing a few $100...

 

[No-one-&-Not-Important]

2 batteries is a fine start. Hell, they're expensive, I get it. But. I'd recommend planning for future expansion by setting up physical space and wiring for a total of 4 batteries, 2 per inverter, so when you're ready to expand, it's just a matter of installation.

For ease of service, I'd recommend a combiner panel. This way, you can isolate one of the two inverters by flipping a breaker, making maintenance much simpler if one needs to go down for servicing. Then, use 4/0 Aluminum cable to run from the combiner panel to the new load center in the garage.

Planning for the future, including for future owners, is always wise. Here's what you'd need:

1. A 200A external meter/disconnect combo (Eaton CMBEB200BTS or CMBEB200BTF)
2. 4/0 AL service entrance cable
3. An inverter combiner panel with two 100A breakers

@green-river When I was considering my wiring diagrams, I realized your comments had something specific in mind.

When you said, "2 batteries per inverter" + "combiner panel" + "disconnecting independently", I think you meant that I should NOT use the inverters in a combined (primary-secondary) config (i.e.: one controls and communicates with the other). Also, I think you wanted the batteries to NOT be on a bus bar connected to both inverters at the same time. Did I read your suggestion correctly; did you recommend to have 2 batteries each INDEPENDENTLY connected to each battery and each inverter independent of the other?

In a separate thread, @wpns indicated when setting it up this way, there were problems with battery charging since the two inverters weren't communicating together. I'd also strand quite a bit of power from the PV panels since they're not all equal strings (my roof arrangement simply won't allow it physically).

Can you @green-river comment on this? I think tying the two inverters in a primary/secondary config and the batteries in a equal length conductor busbar (all + on one busbar and all - on another) would allow all the available solar energy to be used to charge all 4 batteries and allow the inverters to work together better. Of course, the downside is that if the primary goes down, it all goes down and I'd have to reconfigure the system quickly so the secondary becomes the primary (which is a procedure I have two write up anyway so that (like @wpns put it), we're not trying to figure things out in the dark.

Thanks again.

 

[green-river]

When I was considering my wiring diagrams, I realized your comments had something specific in mind.

Yes, I did. Because, I go back and forth on this myself actually.

It's driven by this: IIRC, when inverters are set up in parallel, if the primary fails, all secondary inverters shut down too. The only way to have true redundancy is to set up two completely separate stations—no parallel connection, no shared battery bank.

So, it depends:

1. If you’re away from home for long periods and want full redundancy, a side-by-side setup with separate battery banks for each inverter is the only way. That way, if one system fails, the other keeps running without needing any manual intervention. This feels a bit extreme tho.
2. If you’re at home when there is a hardware failure, you can reconfigure the secondary to run on its own. For this setup, it’s probably just better to have all the benefits of configuring the inverters in parallel so they can work together, share PV, and having them share the same battery bank.

 

[wpns]

IIRC, when inverters are set up in parallel, if the primary fails, all secondary inverters shut down too.

That’s correct, but unfortunately it works the other way around too. If the secondary fails the primary will shut down as well. Have an immediate procedure for switching to grid power and you can figure out what went wrong and recover/reconfigure the inverters at your leisure.

 

[killercarver]

I'm just seeing and catching up on this thread. @No-one-&-Not-Important sounds like we have a very near same setup....2x 12000xps, 4x eg4 wallmounts, a pallet of hyperion 400w bifacials... Nice! (I'm loving the heck out of my system and it's overkill for me, but should last a very long time....and I've been grid free for over 50 days now. I would suggest (cause i'm a nerdy engineer too) getting a Sense power monitor or similar as it was eyeopening to me, my loads, daily usage, etc.....and it will likely help you to find places to become more energy efficient.

I'm running 4 strings of 9 panels here in VA and it's been a near perfect match for voltage and all to the MPPTs.
You can use AC just to charge batteries (based on SOC or voltage for closed vs open loop comms) while still inverting (tested this); and inverter should switch to grid bypass/charge if batteries get low enough (never tested this). See https://diysolarforum.com/threads/12000xp-low-soc-settings-help.97272/#post-1323757

I saw @green-river suggest a heat pump dryer which would be more efficient, but take a good bit longer. Heater in my electric dryer is like a 5kw load when its on, so no issues on my end. Now, I do love my heat pump water heater and I have it scheduled to be on only during solar hours...so free hot water (basically).

I wired each inverter to handle 100A from grid and to deliver 100A output since it's supposed to be able to bypass 100A from grid through it to loads. Manuals and all were a bit confusing on this...

Watch your torque specs in the 12000xp manual; I've email EG4 folks about this with no response that they need to look at these and correct them before someone breaks something. The CHNT breakers call for 31in-lbs. Also, verify the torque on the inverter connections where you can (battery terminals, the ground and neutral bar); I found the inverter neutral barely snug on one of my units and neither torqued anywhere near what Luxpower or EG4 called for in their manuals. The Luxpower SNA 12k is our equivelent, btw; and Eddie/Edwin on here is the US Lux rep too.

A few pics of my setup (before cleaning everything up). I was planning to do 2x 6000XPs right as the 12000XPs were coming out, and I'm so darn happy that I went with the 12000xp's for my all electric home. And yes, I know I haven't met spacing requirements...and I'm in the middle of doing some remodeling.

 

[green-river]

@killercarver this has to be the most beautiful carport in existence. are those repurposed telephone poles?

 

[green-river]

@No-one-&-Not-Important - heard back from EG4 yesterday on a different thread. They confirmed if either the primary or the secondary fails, you'll need to reconfigure to keep going. But they seemed to indicate if the secondary fails, the primary "should" still work. yes, should...

Here's there comment on that thread - https://diysolarforum.com/threads/eg4-6000xp-bypass.90478/#post-1322453