[RE-wrenches] How to sell maximum amount from EG4

Sat Jun 27 05:31:29 PDT 2026

I think you are talking about a dual meter scenario for grid
interconnection (separate buy/sell meters). If that is the case, I would
avoid grid interconnection altogether. The utility company doesn't need to
know what you're up to. The benefit from grid selling would be so small
that it would not really matter unless the array was very large relative to
the load. As Zeke suggested, just set this up as a no-sell site and use the
batteries for maximum self-consumption. If PV is being lost and the battery
reaches the stop discharge limit routinely, suggest more battery capacity.

The EG4 12000XP is a good option for this scenario. It does not grid sell.
It's just like a UPS when paired with a battery, but it can be used to
self-consume solar. The flagship EG4 inverters can be set up this way as
well, but cannot guarantee there will be no leakage back to the grid (if
large loads suddenly shut off during high solar production, especially if
the battery is full).

Jason Szumlanski
Principal Solar Designer | Florida Solar Design Group
NABCEP Certified Solar Professional (PVIP)
Florida State Certified Solar Contractor CVC56956
Florida Certified Electrical Contractor EC13013208

On Sat, Jun 27, 2026 at 8:21 AM Christopher Warfel via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Thanks Zeke, I just saw this and will respond with some ideas.  Chris
> On 6/26/2026 6:06 PM, Zeke Yewdall via RE-wrenches wrote:
>
> This sounds like the old buy all sell all system with two meters.  I
> didn't realize any utilities were still doing this.  But the way that we'd
> do it on a grid-tie system was have one meter measuring production that
> then connected into the grid on the utility side of the meter going to the
> house.  During a sunny day, the energy used by the house would first be
> sold to the utility through the production meter, then bought right back
> through the normal loads meter.
>
> Doing a battery backup system would, I think, be wired up the same way.
> The PV array would have its own grid-direct inverter selling power to the
> grid, and then the battery backup system would draw power from the grid for
> charging -- it would be set up as a UPS type system, not knowing that any
> solar existed at all.
>
> If the grid went down, you would not be able to power the house or charge
> the batteries from the solar, as it would be connected on the dead grid
> side of any transfer switches from the backup power, and I think this would
> meet the utilities intent -- if the grid is down, they cannot purchase any
> electricity, so therefore, generating electricity to recharge your
> batteries or use would not be allowed.
>
> Frankly, if faced with a tarriff like this, I would seriously look into
> what it would take to get rid of the grid connection entirely and do an
> actual off-grid system.  I figure that most batteries right now cost about
> 4 to 5 cents/kWh for energy stored then used.  So it would depend on the
> load profile and how much was used during the daytime and how much at
> night, but if the buy rate is more than 2 or 3 cents more than the sell
> rate, I would think it would be cheaper to invest in batteries and pay 0
> markup during the daytime, and 4 or 5 cents battery cost at nighttime,
> rather than paying more than 2 or 3 cents markup all the time.
>
> Usually, even when faced with very unattractive buy/sell rates, I still
> recommend that people maintain their grid connection, even if only to use
> it in place of a standby generator fill in during winter weather.  Even
> paying a $50/month standby charge to maintain a grid connection you almost
> never use can be cheaper than maintaining an actual physical generator.
> But if you aren't allowed to even use your own solar power on site without
> incurring their markup, then that could be a different story.
>
> Zeke
>
> On Fri, Jun 26, 2026 at 10:39?AM Christopher Warfel via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
> > > Our local utility has a requirement that ALL generation be sold to them
> > at avoided cost, and that ALL purchases be made at tariff rate.  A couple
> > of years ago before installing an EG4 system (which I did my first one
> this
> > past year), I told the president of the coop that I did not think that
> was
> > possible with multi mode systems.  I've tried a lot of different settings
> > in the EG4 but it seems not to make a big difference.
> >
> >
> > Does anyone have knowledge of how to do this?  Signature Solar did not
> > have a definitive answer, and what we have tried so far, has not really
> > produced the results I was hoping for.
> >
> >
> > Thank you, Chris
> >
> > >
> > --
> > Christopher Warfel, PE
> > ENTECH Engineering, Inc.
> > PO Box 871, Block Island, RI 02807
> > (401) 447-5773
>
> On Fri, Jun 26, 2026 at 1:13 PM <re-wrenches-request at lists.re-wrenches.org>
> wrote:
>
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>> Today's Topics:
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>>    1. How to sell maximum amount from EG4 (Christopher Warfel)
>>    2. Re: How to sell maximum amount from EG4 (Dave Tedeyan)
>>
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>> ----------------------------------------------------------------------
>>
>> Message: 1
>> Date: Fri, 26 Jun 2026 10:36:32 -0400
>> From: Christopher Warfel <cwarfel at entech-engineering.com>
>> To: re-wrenches at lists.re-wrenches.org
>> Subject: [RE-wrenches] How to sell maximum amount from EG4
>> Message-ID:
>>         <adcab7b2-1d88-4896-af75-3bc90406546d at entech-engineering.com>
>> Content-Type: text/plain; charset=UTF-8; format=flowed
>>
>> > Our local utility has a requirement that ALL generation be sold to them
>> at avoided cost, and that ALL purchases be made at tariff rate.  A couple
>> of years ago before installing an EG4 system (which I did my first one this
>> past year), I told the president of the coop that I did not think that was
>> possible with multi mode systems.  I've tried a lot of different settings
>> in the EG4 but it seems not to make a big difference.
>>
>>
>> Does anyone have knowledge of how to do this?? Signature Solar did not
>> have a definitive answer, and what we have tried so far, has not really
>> produced the results I was hoping for.
>>
>>
>> Thank you, Chris
>>
>> >
>> --
>> Christopher Warfel, PE
>> ENTECH Engineering, Inc.
>> PO Box 871, Block Island, RI 02807
>> (401) 447-5773
>>
>>
>>
>> ------------------------------
>>
>> Message: 2
>> Date: Fri, 26 Jun 2026 10:42:53 -0400
>> From: Dave Tedeyan <dave at sungineersolar.com>
>> To: cwarfel at entech-engineering.com,  RE-wrenches
>>         <re-wrenches at lists.re-wrenches.org>
>> Subject: Re: [RE-wrenches] How to sell maximum amount from EG4
>> Message-ID:
>>         <CAM3Q7f1Qsbhpi=
>> hO6BXe8nkQH-WvLkHrJSSm-B_-rK_AW9FnVw at mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> You can try contacting EG4 directly. I've had good luck talking to them as
>> well when I have had questions. They were good about helping me derate the
>> grid sell for a couple inverters to stay below our utilities residential
>> limit, and then signing a form for us to give to the utility.
>>
>> Cheers,
>> Dave
>>
>> On Fri, Jun 26, 2026 at 10:39?AM Christopher Warfel via RE-wrenches <
>> re-wrenches at lists.re-wrenches.org> wrote:
>>
>> > > Our local utility has a requirement that ALL generation be sold to
>> them
>> > at avoided cost, and that ALL purchases be made at tariff rate.  A
>> couple
>> > of years ago before installing an EG4 system (which I did my first one
>> this
>> > past year), I told the president of the coop that I did not think that
>> was
>> > possible with multi mode systems.  I've tried a lot of different
>> settings
>> > in the EG4 but it seems not to make a big difference.
>> >
>> >
>> > Does anyone have knowledge of how to do this?  Signature Solar did not
>> > have a definitive answer, and what we have tried so far, has not really
>> > produced the results I was hoping for.
>> >
>> >
>> > Thank you, Chris
>> >
>> > >
>> > --
>> > Christopher Warfel, PE
>> > ENTECH Engineering, Inc.
>> > PO Box 871, Block Island, RI 02807
>> > (401) 447-5773
>> >
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>
>
> --
> Zeke Yewdall
> PV Engineer
> NABCEP #031508-89
> zeke at darkforestsolar.com
> 303-523-3592
>
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> --
> Christopher Warfel, PE
> ENTECH Engineering, Inc.
> PO Box 871, Block Island, RI 02807
> (401) 447-5773
>
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