EG4 18kPV vs 12000XP vs FlexBOSS21

[BTOdell]

Hello everyone,

I've been planning to build an off-grid solar power system for over a year now. It will be located on my newly purchased property in south central Alaska. There's no power to the property and I don't plan on bringing power to the property in the foreseeable future. Although, I do need to be able to connect a generator when the long winter nights come and solar isn't enough.

I was originally considering one EG4 18kPV with around 16-20kw of solar (30 bifacial panels). I don't technically need the hybrid functionality, but I liked that it was one unit and had low idle consumption compared to using multiple smaller "off-grid inverters". The idle consumption of the 18kPV is apparently around 70w, if I got several 6000XP each at 50w, that's 100-150w. Multiple units also take up more wall space. The 18kPV also supports a max of 600VDC for solar; this should allow me to have 3 strings of 10 panels.

Lately, I've noticed there are some new hybrid and off-grid inverters on the market. The EG4 12000XP and the EG4 FlexBOSS21. I've read some of the other threads comparing these inverters, but I'd like some advice based on my situation.

First, the EG4 FlexBOSS21 seems better than the 18kPV is every way. More PV input (21kw vs 18kw), same 12KW output, same 600VDC maximum, lower 65w idle consumption. It seems like the FlexBOSS21 eats the 18kPV's lunch. Am I missing something? The FlexBOSS21 doesn't have a dedicated GEN terminal, but could a generator be connected to the grid terminals instead?

Second, the EG4 12000XP. Unfortunately, the max PV voltage is 480 instead of 600 - but I suppose I could reconfigure my panels into 4 strings. The price is nearly half of the 18kPV, I could buy two if I wasn't concerned about idle consumption. It would be nice to have a backup inverter if one failed... Also, I'm really confused because images of the 12000XP show it has a GEN and GRID wire connections. How can it be off-grid if it has terminals for the grid?



I plan to pair the inverter with the EG4 WallMount Indoor Battery, maybe 2 of them.

What do you guys think is the most cost efficient and effective solution for my use case? Thanks!

 

[lordryck]

I've been looking at the FlexBOSS21 quite closely. As you say, it's more powerful than the 18k. Differences: It doesn't have a front display--you must control it with the app. And it doesn't have the built-in 200amp transfer switch that the 18kPV does, but you don't need that anyway. They've moved that functionality into the GridBOSS. You can use the grid connection for your generator. Configure the system as a "Micro-Grid."

 

[wdwtx2.0]

Off grid inverters have grid input terminals.
They will only use grid power, or solar/battery power.
Not both at once, AFAIK.
If your batteries get too low, and PV input is too low, it will switch to grid power.
They cannot export power to the grid because they operate either/or. AFAIK.

The 12000XP sounds ideal for your application.
It can power your AC loads with 12000 watts of power, while simultaneously charging your batteries with 12000 watts.
That is a HUGE improvement over other AIO inverters.
35 amps per MPPT means you can run 3 strings per MPPT after a combiner box.
That helps make up for the lower allowable voltage.
You can over-panel up to 28000 watts.

 

[BTOdell]

I've been looking at the FlexBOSS21 quite closely. As you say, it's more powerful than the 18k. Differences: It doesn't have a front display--you must control it with the app. And it doesn't have the built-in 200amp transfer switch that the 18kPV does, but you don't need that anyway. They've moved that functionality into the GridBOSS. You can use the grid connection for your generator. Configure the system as a "Micro-Grid."

But now you're talking about buying both the FlexBOSS21 and the GridBOSS, which would come out to well over the price of just the 18kPV. Plus would need to find wall space that could be used for more batteries down the road.

 

[BTOdell]

Off grid inverters have grid input terminals.
They will only use grid power, or solar/battery power.
Not both at once, AFAIK.
If your batteries get too low, and PV input is too low, it will switch to grid power.
They cannot export power to the grid because they operate either/or. AFAIK.

The 12000XP sounds ideal for your application.
It can power your AC loads with 12000 watts of power, while simultaneously charging your batteries with 12000 watts.
That is a HUGE improvement over other AIO inverters.
35 amps per MPPT means you can run 3 strings per MPPT after a combiner box.
That helps make up for the lower allowable voltage.
You can over-panel up to 28000 watts.

If I plug the generator into the GEN port, can it power loads and charge the battery at the same time?

I'm really starting to consider going with two 12000XP and two wall batteries. I'll just have to accept the extra idle consumption of two inverters.

 

[wdwtx2.0]

If I plug the generator into the GEN port, can it power loads and charge the battery at the same time?

I'm really starting to consider going with two 12000XP and two wall batteries. I'll just have to accept the extra idle consumption of two inverters.

I have not studied the user manual, but I would assume it could.
It will pass through 100A to your load panel.
You can use a generator as the grid input, or use the generator input.

 

[Brucey]

But now you're talking about buying both the FlexBOSS21 and the GridBOSS, which would come out to well over the price of just the 18kPV. Plus would need to find wall space that could be used for more batteries down the road.

For off grid I'm pretty sure you can use a flexboss 21 by itself without a gridboss.

 

[zanydroid]

If it's off-grid, OP doesn't need outdoor rating (which presumably is the case because 12000XP is on the menu), and Alaska is some libertarian bear populated paradise like I have in my headcanon, why pay the premium for the extra certifications on the 18kpv/flexboss21 family?

If I plug the generator into the GEN port, can it power loads and charge the battery at the same time?

This is actually a pretty subtle question with sub-cases, and from what you said it's not possible to get a solid answer.

Simplified strawman: If your generator is large enough to match the inverter's output power as well as max battery charge power, certainly.

If it is not, and you have to configure some kind of generator boost situation, it comes down to understanding the intimate details of what the inverter hardware + firmware is capable of. People have been burned by every model/brand, by not understanding what they can actually do relative to their specific generators and generator use case.

And I specifically call out the hardware and firmware because:
- HF inverter/charger needs to be able to reverse direction quickly enough in some usage scenarios.
- Firmware may not let you configure what you want, even if the flesh is willing

 

[BTOdell]

Alaska is some libertarian bear populated paradise

 

[BTOdell]

This is actually a pretty subtle question with sub-cases, and from what you said it's not possible to get a solid answer.

Let's say the generator is 9kw and load is only 5kw. Can you not say whether the 12000XP will put 4kw towards the battery while also passing the 5kw through to support the load?

 

[zanydroid]

Let's say the generator is 9kw and load is only 5kw. Can you not say whether the 12000XP will put 4kw towards the battery while also passing the 5kw through to support the load?

I think that specific case will work pretty straightforward, if you can configure a maximum battery charge current in the firmware.

Two cases that will require more thinking is, how smart is the inverter when you go to a 10kW load. How smart is the inverter when you go to a 21kW load.

10kW, the inverter can be smart in one way, by taking the full load (in the worst case), without attempting to parallel balance with the generator (gen shave / gen boost mode).

For 21kW, the inverter has to balance its output parameters to not exceed the 9kW of the generator (IE, let's call it, "increase the voltage"). If it cannot set its parameters to this balance point, the generator will overload.

Even spicier is if you want the generator always running at 9kW, but the load is such that the inverter has to flip back and forth between charging and inverting. Imagine load of 0kW for 5 min, then 12 kW for another 5 min, then back to 0 kW. If the generator can surge to 12kW for a fraction of a second without dying, then this situation should be OK for any gen boost capable inverter. If the generator will insta-fail, maybe not.

I think the generator is more robust than AC coupling to a grid tie inverter (which is more likely to get upset in this case, because of less inertia [a spinning generator would have some inherent inertia ; not sure about an inverter generator] / surge capability)

 

[green-river]

Maybe get a chargeverter and charge the batteries from the generator aside from the inverter. To avoid the nuanced use cases.

 

[zanydroid]

Maybe get a chargeverter and charge the batteries from the generator aside from the inverter. To avoid the nuanced use cases.

I suspect it’s fine out of the box if not expecting to gen boost.

And if you use a chargeverter you won’t be able to boost past the limit of the inverter (you can boost past battery BMS limit but that’s weird).

The good thing about chargeverter is that you can retrofit the fix in, if the hybrid or AIO doesn’t work nicely

 

[BTOdell]

I've been comparing the spec sheets between the three AIO inverters and I think I found out why the 12000XP is half the price compared to the other two. The 18kPV has the most impressive efficiency, with the FlexBOSS21 coming second, and the 12000XP being the worst.

18kPV:
CEC 96.9%
MAXIMUM EFFICIENCY (PV TO GRID) 97.5%
MAXIMUM EFFICIENCY (BATTERY TO GRID) 94%
MAXIMUM EFFICIENCY (PV TO BATTERY) 99.9%
IDLE CONSUMPTION (NORMAL | STANDBY MODE) ~70W | ~18W

FlexBOSS21:
CEC 96.9%
MAX. EFFICIENCY (PV TO GRID) 97%
MAX. EFFICIENCY (BATTERY TO GRID) 94%
MAX. EFFICIENCY (PV TO BATTERY) 94.5%
IDLE CONSUMPTION <65W

12000XP:
MAXIMUM EFFICIENCY (MPPT) 99%
MAXIMUM EFFICIENCY (PV TO BATTERY) 92.8%
MAXIMUM EFFICIENCY (AC TO BATTERY) 92.5%
MAXIMUM EFFICIENCY (PV TO LOADS) 93.5%
MAXIMUM EFFICIENCY (BATTERY TO LOADS) 90.2%
IDLE CONSUMPTION (STANDBY MODE)* <70W

(These are taken from the spec sheet PDFs hosted by Signature Solar)

It seems that the 18kPV and the FlexBOSS21 have the same overall (CEC) efficiency, except the 18kPV claims 99.9% from PV to battery but the FlexBOSS21 has 94.5%. I would expect this to impact the CEC score of the FlexBOSS21, but it hasn't?

Then we come to the 12000XP. I was nearly sold on this off-grid inverter and going to buy it instead of the 18kPV, but off-grid efficiency is important. After the power goes from PV to battery to loads, we're at a combined 83.7% max efficiency.

Is it reasonable to be this obsessive over efficiency? Do you think this is reason to choose the 18kPV or FB21 instead of the 12000XP?

 

[zanydroid]

The cost difference is primarily due to which certifications the systems have.

The other way to address efficiency is to take the $3500 price difference and put it into solar panels and batteries. :mic drop:

99.9% efficiency from PV to battery is probably kind of impossible. And I doubt CEC efficiency counts it, I’m guessing CEC efficiency is a grid tie metric going by the primary mission of CEC for a long time (grid tie stuff)

 

[Brucey]

The difference is related to the hybrid capability of the fb21 and 18kpv. 18kpv also has 200a pass thru etc. If you need grid sellback etc then the 12000xp isn't a good candidate. Fb21 has 50% more motor start capability than 18kpv.

 

[ddxv]

I have the 12000xp off grid on a bad little portable Honda generator. We can use genboost to power the house and charge the batteries. We ended up ordering a chargeverter since the likely dirty THD of the portable generator is much higher than the inverter wants.

My issue with the 12000xp has been that it's software pretty lacking (android app issues and Wi-Fi dongle issues).

 

[ddxv]

Actually, one more thing to add: despite being billed as an off grid inverter, I don't really think the EG4 ecosystem was used to actual offgrid. Case in point the 12000XP generator assumed use case is backup power in case of grid failure.

Still it's worked ok for us so far.

 

[mciholas]

18kPV:
...
MAXIMUM EFFICIENCY (PV TO BATTERY) 99.9%

Nope, fails sanity check.

Around 93% to 95% is reasonable.

Is it reasonable to be this obsessive over efficiency?

Partly. Inefficiency causes two problems, loss of energy and generation of heat. Both are bad, usually. More efficient is better to the point it doesn't cost so much it negates its value.

Do you think this is reason to choose the 18kPV or FB21 instead of the 12000XP?

The 12000XP does seem a little less efficient, but between the FB21 and 18Kpv, there's no real difference.

Something to keep in mind is that these numbers are at some operating point which is not specified. It might be at full power. If so, the losses tend to increase with higher power, so a FB21 being slightly less at its higher power might mean it is as good as the lower power 18Kpv. A 0.5% efficiency difference is also very hard to measure and likely within the error band of the measurement.

What I would want to see is the curve of efficiency versus power output and see how well these devices work at "part throttle".

Mike C.

 

[alvitdk]

I don't know much about the 18k but have the flexboss21 and gridboss, but connected to the grid. Not sure about the 18k but the gridboss will start your generator at conditions that can be programmed, including time, battery charge, etc.

 

[miran90]

I measured the efficency I think ac charge is more efficient than discharge pv is the most efficient though.

 

[CaySol]

I don't know much about the 18k but have the flexboss21 and gridboss, but connected to the grid. Not sure about the 18k but the gridboss will start your generator at conditions that can be programmed, including time, battery charge, etc.

How is your system working out for you? Excited to install mine soon.

 

[alvitdk]

How is your system working out for you? Excited to install mine soon.

Working great and trouble free since the install, I’m happy with the production and integration

 

[No-one-&-Not-Important]

If I plug the generator into the GEN port, can it power loads and charge the battery at the same time?

I'm really starting to consider going with two 12000XP and two wall batteries. I'll just have to accept the extra idle consumption of two inverters.

I can confirm (asked EG4 tech after I was confused and @green-river and others suggested I check): It is NOT possible to run GEN & power loads at the same time. It's one or the other, not both simultaneously. It will charge batteries while GEN is running though.

The manual section 7.3 is very ambiguous. It says "Grid or PV and Batteries" and should add the phrase, "but not both at the same time".

 

[No-one-&-Not-Important]

I don't know much about the 18k but have the flexboss21 and gridboss, but connected to the grid. Not sure about the 18k but the gridboss will start your generator at conditions that can be programmed, including time, battery charge, etc.

Do you know or did you ever consider combining the FB21 & 12000XP together and configure in parallel? I'm considering mixing these two.