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Zero Eport and the EG4 18Kpv

FilterGuy

FilterGuy

Solar Engineering Consultant - EG4 and Consumers
Joined
Nov 26, 2019
Messages
7,939
Location
Los Gatos CA
There has been a lot of discussion about ‘Zero Export’ on the 18Kpv and I would like to summarize what is going on.

General Points:
  • The term ‘Zero Export’ is used throughout the industry to talk about preventing power from being exported to the grid. The reality is that Zero Export is a bit of a misnomer because no hybrid inverter currently available can achieve true zero export. All of the hybrid inverters I have data on have a margin of error. Generally speaking, Hybrid inverters can get it down to 100W or less. However, if there is a load on the output, this will go away.

    Practically all households have a constant background load of over 200W so they will never see a sustained export. (It is possible that there may be momentary exports when a very large load shuts off and the inverter races to adjust)

  • Exporting power is only an issue when the inverter is installed in a situation where the Utility does not allow export. In all other cases, the amount of export is negligible and makes no real difference in the performance of the system.

    The primary reason a utility does not allow export is that their systems are not set up to handle the extra power. Consequently, if a utility notices an export they will likely do an inspection, and when they determine that it is a small export, many sign off on the installation anyway.

    Note: The utilities also have safety concerns but those are covered by UL listings for Grid Interactive inverters and are somewhat separate from the Zero Export issue.

The 18KPV-specific information.
  • The 18KPV can see as high as 100W export in the no-load scenario and the EG4 engineers tell me they are working on reducing it
  • EG4 reports that after deploying over 500 systems, there are no reports of a Utility flagging an export issue on the 18Kpv.
  • The EG4 engineers tell me they are working on a firmware update that has a setting to turn the inverter into an off-grid inverter when loads are under 1000w, and reconnect as grid assist is needed. When in this mode, the inverter never powers from the inverter and the grid at the same time while at that low of a wattage.
    (I do not have further information on the characteristics of the transition from on-grid to off-grid and back.)
 
FilterGuy said:
There has been a lot of discussion about ‘Zero Export’ on the 18Kpv and I would like to summarize what is going on.

General Points:
  • The term ‘Zero Export’ is used throughout the industry to talk about preventing power from being exported to the grid. The reality is that Zero Export is a bit of a misnomer because no hybrid inverter currently available can achieve true zero export. All of the hybrid inverters I have data on have a margin of error. Generally speaking, Hybrid inverters can get it down to 100W or less. However, if there is a load on the output, this will go away.

    Practically all households have a constant background load of over 200W so they will never see a sustained export. (It is possible that there may be momentary exports when a very large load shuts off and the inverter races to adjust)

  • Exporting power is only an issue when the inverter is installed in a situation where the Utility does not allow export. In all other cases, the amount of export is negligible and makes no real difference in the performance of the system.

    The primary reason a utility does not allow export is that their systems are not set up to handle the extra power. Consequently, if a utility notices an export they will likely do an inspection, and when they determine that it is a small export, many sign off on the installation anyway.

    Note: The utilities also have safety concerns but those are covered by UL listings for Grid Interactive inverters and are somewhat separate from the Zero Export issue.

The 18KPV-specific information.
  • The 18KPV can see as high as 100W export in the no-load scenario and the EG4 engineers tell me they are working on reducing it
  • EG4 reports that after deploying over 500 systems, there are no reports of a Utility flagging an export issue on the 18Kpv.
  • The EG4 engineers tell me they are working on a firmware update that has a setting to turn the inverter into an off-grid inverter when loads are under 1000w, and reconnect as grid assist is needed. When in this mode, the inverter never powers from the inverter and the grid at the same time while at that low of a wattage.
    (I do not have further information on the characteristics of the transition from on-grid to off-grid and back.)
Click to expand...
Very interested to understand whether the ‘disconnect from grid under 100kW of load’ function remains synced to grid after disconnect so that when reconnecting, transitioning from inverter power back to grid power has no impact on any loads…
 
FilterGuy said:
The EG4 engineers tell me they are working on a firmware update that has a setting to turn the inverter into an off-grid inverter when loads are under 1000w, and reconnect as grid assist is needed. When in this mode, the inverter never powers from the inverter and the grid at the same time while at that low of a wattage.
Click to expand...
Thanks for the writeup. This is what I was wondering about because older "hybrids" like the Outback VFX3648 would never export to grid since you were either in an off-grid mode, UPS mode, or selling back. They even talked about making a "zero export mode" that would have required current transformers to try and keep the export to 0 but did not find enough interest in that feature back then. It is this type of mode where you use a current transformer to try to keep load and production equal where the issue is. But in all other modes there should never be an issue and seems to be what they are trying to address now.
 
FilterGuy said:
  • The EG4 engineers tell me they are working on a firmware update that has a setting to turn the inverter into an off-grid inverter when loads are under 1000w, and reconnect as grid assist is needed. When in this mode, the inverter never powers from the inverter and the grid at the same time while at that low of a wattage.
    (I do not have further information on the characteristics of the transition from on-grid to off-grid and back.)
Click to expand...
I'm not sure how much this will help as many of the loads that turn off suddenly and have big impact on export, are large loads.
for example,
-an electric water heater will pull 4500 watts, and then suddenly go to zero
-an electric clothes dryer, while its running, continuously cycles between 5700w and 0w
dryer.jpg
 
:) I was just curious what an Eport was. But I guess having zero of them on the EG4 18K is a good thing. Unless you need it to connect up your latest Apple doodad.
 
Why is it that people are using a hybrid inverter when they want zero export ? Is it because there are no large enough off grid/grid assist inverters in these large sizes ?
for a given size, hybrids cost more than off grid inverters
 
Texican said:
Why is it that people are using a hybrid inverter when they want zero export ? Is it because there are no large enough off grid/grid assist inverters in these large sizes ?
for a given size, hybrids cost more than off grid inverters
Click to expand...
Because they don't necessarily have an agreement with the utility company to export. Big trouble for exporting if you don't have one.
 
cs1234 said:
Because they don't necessarily have an agreement with the utility company to export. Big trouble for exporting if you don't have one.
Click to expand...
Yes, I get that, but why not use an off grid inverter.
I thought hybrids were for grid tie systems with batteries
 
Texican said:
Yes, I get that, but why not use an off grid inverter.
I thought hybrids were for grid tie systems with batteries
Click to expand...
Because a (hybrid) grid tied inverter with limiter can offset your loads used on any circuits in your building below where you put the CT 's. You don't have to have a critical load panel below the inverter. Just hook it up where ever you like in the wiring, run the CT 's to the incoming AC mains and inject away. It all goes downhill if the hybrid reacts too slow, has weird programming or otherwise injects more than it's supposed to.

Safest to have it set to offset just some of the load, and not attempt to hit zero.. attempting to hit zero is where you will run into trouble. I try to have mine only offset my consistent base loads, with a healthy margin left as buffer. Anything really huge like air conditioners and dryers and such, I don't worry about. Base load adds up over time anyway. It would depend on what your power usage is like though.. I have about a 1000-1500 watt base load in my house all the time because of my wiener kids / wife. :)
 
Last edited:
Updated this post as I went back to look at the system again. It's been about a months since I even went in the electrical room.
My Sol-Ark 12K is not back feeding. I can select how many Watts it draws from the Grid so as to prevent any chance of back feeding.
I set it to 20 Watts, so it is always drawing 20 watts from the grid which seems to offset almost half of the 60 Watt power that the Inverter uses when in operation.
I remember when we first set it up we played with the sell back feature and had it set to 80 Watts to test the Inverter for a future Net Metering agreement. That Alerted them because two guys showed up about 3 days later wanting to inspect the system. They found nothing because we had only tested it for a few hours and then turned off the Sell back settings.

PVSell.jpg
 
Last edited:
cs1234 said:
Because a (hybrid) grid tied inverter with limiter can offset your loads used on any circuits in your building below where you put the CT 's. You don't have to have a critical load panel below the inverter. Just hook it up where ever you like in the wiring, run the CT 's to the incoming AC mains and inject away. It all goes downhill if the hybrid reacts too slow, has weird programming or otherwise injects more than it's supposed to.

Safest to have it set to offset just some of the load, and not attempt to hit zero.. attempting to hit zero is where you will run into trouble. I try to have mine only offset my consistent base loads, with a healthy margin left as buffer. Anything really huge like air conditioners and dryers and such, I don't worry about. Base load adds up over time anyway. It would depend on what your power usage is like though.. I have about a 1000-1500 watt base load in my house all the time because of my wiener kids / wife. :)
Click to expand...
Yep and you don't have to worry about starting large inductive loads or flickering led lights .

I like your idea of coming in slightly below daytime base loads. My base load is 220w but I bet my v daytime loads are closer to 2kw
 
Last edited:
With the digital meeters the utilities can see *any* export, but they can also see size and duration. Some will be paranoid and check on it. Others won't care as long as the export remains small. I suspect that as hybrid inverters become more common they will get used to the small backfeed and fewer of them will be alarmed. (Well, I at least hope it goes that way)

However, they all want to be sure any grid interactive inverters are UL listed. Every jurisdiction and utility will have slightly different processes for ensuring UL listings.
 
FilterGuy said:
With the digital meeters the utilities can see *any* export, but they can also see size and duration. Some will be paranoid and check on it. Others won't care as long as the export remains small. I suspect that as hybrid inverters become more common they will get used to the small backfeed and fewer of them will be alarmed. (Well, I at least hope it goes that way)

However, they all want to be sure any grid interactive inverters are UL listed. Every jurisdiction and utility will have slightly different processes for ensuring UL listings.
Click to expand...
Oh mine is a brand new digital Meter and they can see any export. I think mine was set to 80W originally and it triggered an alarm and they came to inspect it.
I assume they do use a small Margin so as not to create to many false alarms. It seems like 20W is not enough to Trigger an alert but 80W is enough.
 
1201 said:
Yep and you don't have to worry about starting large inductive loads of flickering led lights .

I like your idea of coming in slightly below daytime base loads. My base load is 220w but I bet my v daytime loads are closer to 2kw
Click to expand...
Even a 200watt base load at $.10/kwh is 50 cents a day in savings.. :ROFLMAO:
 
robby said:
My Sol-Ark 12K will almost zero out. It is back feeding maybe 20 Watts.
It's not enough to trigger the power companies alerts.
Click to expand...
My cheapo GTIL2 inverters allow the grid to constantly supply a sustained 7-25w and only backfeed for a milisecond when loads shut off.. the electric company can still see even this small amount of backfeed because they see an accumulation over time. If your system is already inspected and or permitted then they don’t care. If the amount is small enough as is with my inverters and most likely your Solark then they might not notice until they see solar panels and start looking into what u got going on
 
1201 said:
5 Sun hours. Only 10 cents a day lol ?
Click to expand...

You don't run the GTIL directly off solar panels. You use another SCC to charge batteries and run the GTIL off that.. then you have 24 hours of low wattage coverage.
 
cs1234 said:
You don't run the GTIL directly off solar panels. You use another SCC to charge batteries and run the GTIL off that.. then you have 24 hours of low wattage coverage.
Click to expand...
I like the strategery
 
Hello all

I just had my final inspection and bi-directional meter installed.

I was talking to the technician as he was replacing my old digital meter and he said that the digital meter they replaced did not run backward when back fed but instead ran forward charging you for any back fed power. I was somewhat surprised at that disclosure.

Bob
 
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