[RE-wrenches] Will IQ8 microinverters backfeed a generator during grid interruptions

[William Bryce]

If the AC coupled exported energy is more than the generator produced
energy, it can destroy the generator controller.
That is why most AIO inverters have a relay on the dedicated AC coupling
input. It will open the relay if the inverter sees generator power.

The MNP AIO will allow both inputs, but will open the relay if the AC
coupled power increases to 20% of the Generator input (firmware dependent).


On Wed, Jan 21, 2026 at 2:27 PM Jason Szumlanski via RE-wrenches <
re-wrenches at lists.re-wrenches.org> wrote:

> Enphase IQ8 microinverters will absolutely leak some power back to the
> grid when set to a no-export grid profile. How much, and if that is
> detrimental to the generator is another question. I suspect if the
> generator is large enough relative to the PV array, the impact will be nil,
> but I would not take the risk.
>
> I don't think the fast switching really does the trick in terms of not
> exporting. That function relies on the consumption CTs connected to the
> Gateway, which in turn communicates with the microinverters. Aside from the
> CTs not being totally accurate, I don't see how that communication loop
> could be fast enough.
>
>
> 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 Wed, Jan 21, 2026 at 12:09 PM scot.arey--- via RE-wrenches <
> re-wrenches at lists.re-wrenches.org> wrote:
>
>> Good day,
>>
>> I many years ago watched the fast-switching capabilities of the IQ-8
>> microinverters to produce only what demanded of the MI, and wondered if it
>> might have application in a grid-tied system that is served by a
>> whole-house generator.
>>
>> We have the opportunity to install grid-tied-only array of 24 IQ8 but all
>> the MIs will be on the customer side of an auto-transfer switch and
>> generator. We want to leverage using existing building wiring to carry the
>> solar and all solar sizing meets the 120% rules.
>>
>> But I know that grid-tied solar on the customer load-side of the transfer
>> switch means no place for full solar power production to flow to when the
>> grid is not available...but  then I thought back to that fast switching
>> capability: is there a way to ensure the IQ8 don't backfeed a generator
>> when it is operating for a grid anomaly?
>>
>> I suspect the answer is "are you nuts???" but that video of capability
>> got me thinking, "why not?" and if not, how is it - what tells the MI to
>> cease production? - when it is within a full and proper ISC/ESS system
>> design?
>>
>>
>>
>> *Howard "Scot" Arey*
>> *Owner, Solar CenTex*
>>
>> NABCEP PV Installation Professional
>> TECL 29755
>> 254-300-1228
>>
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