Micro-inverters vs DC Optimizers

[tkripala]

Hi all! I'm close to deciding on the configuration of a 7.3 kW system (LG320W - 23 panels) but am having a bit of a back-and-forth on Enphase S280 micro-inverters vs SolarEdge DC optimizers. Initially, I had decided on the Enphase but then came across a few mentions of output clipping. I'm not sure how much of this I will see but need to understand if I went with the DC optimizers, would that eliminate the possibility of clipping and help me increase the overall yield?

[ButchDeal]

Hi all! I'm close to deciding on the configuration of a 7.3 kW system (LG320W - 23 panels) but am having a bit of a back-and-forth on Enphase S280 micro-inverters vs SolarEdge DC optimizers. Initially, I had decided on the Enphase but then came across a few mentions of output clipping. I'm not sure how much of this I will see but need to understand if I went with the DC optimizers, would that eliminate the possibility of clipping and help me increase the overall yield?

short answer is yes. If the SolarEdge system is designed correctly they should use at least P320 optimizers capable of 320W and well we would use the SE7600 inverter capable of 7.6kw as well as upgradable to StorEdge battery backup. Some other installers might use the SE6000 which could have some slight clipping depending on the arrangement of your solar modules but would be considerably less clipping as this would be total system and not on individual modules like micro inverters.

There is also the financial health of enphase to consider.

[sensij]

Clipping is probably inconsequential... you aren't going to lose a meaningful amount of energy if LG 320's are paired with S280's. If the price is the same either way, you would be better served to just pick the architecture you like best (or any other differentiating factor you consider important); the energy value difference may be just a few dollars a year.

[tkripala]

short answer is yes. If the SolarEdge system is designed correctly they should use at least P320 optimizers capable of 320W and well we would use the SE7600 inverter capable of 7.6kw as well as upgradable to StorEdge battery backup. Some other installers might use the SE6000 which could have some slight clipping depending on the arrangement of your solar modules but would be considerably less clipping as this would be total system and not on individual modules like micro inverters.

There is also the financial health of enphase to consider.

The installer quoted me an SE6000 and as I read through the spec sheet it did seem to me to be undersized but was assured by the installer that it can handle up to a max of 8.1kW. I'm not sure how much a larger inverter would add to the cost (right now, I'm at just under $3.50/W which seems to be around the average here in the SF Bay Area for LG320's and either Enphase/SolarEdge).

[GRickard]

Not sure what your installer would raise the price for the upgrade, but the retail difference is about $180 between the two inverters.

[ButchDeal]

The installer quoted me an SE6000 and as I read through the spec sheet it did seem to me to be undersized but was assured by the installer that it can handle up to a max of 8.1kW. I'm not sure how much a larger inverter would add to the cost (right now, I'm at just under $3.50/W which seems to be around the average here in the SF Bay Area for LG320's and either Enphase/SolarEdge).

I have taken the SE6000 off of our install option list. There is little reason to install it. the breaker size is almost the same as the SE7600, the SE7600 is more capable and can be upgraded to the StorEdge. With the difference in cost so small, we just don't bother with the SE6000.

Though the SE6000 can have up to 8.1kw connected to it, it can not invert that much.
It does not mean though that it will clip. If all your modules are facing south and unshadowed around the middle of the day you might have some clipping.
Given any shadows, or modules facing different directions, it would be unlikely to clip.

[brucet9]

One further thing to consider is the MPPT operating range of optimizers vs micro inverters. Your chosen LG modules max voltage is 40.9 Voc.

Enphase S280 MPPT range is 27 to 37 volts. This guy won't deliver any power until it sees 27V DC from the module. Voltage under load will certainly be less than open circuit, so it may not exceed the upper limit of the S280.

Solar Edge P320 optimizer MPPT range is 8 to 48 volts. It should, therefor, begin delivering power earlier in the morning and continue later in the afternoon than the micro inverter would. The later in the afternoon you can continue generating power, the higher the per kWh rate you can earn from the PoCo on net metering.

[solardreamer]

One further thing to consider is the MPPT operating range of optimizers vs micro inverters. Your chosen LG modules max voltage is 40.9 Voc.

Enphase S280 MPPT range is 27 to 37 volts. This guy won't deliver any power until it sees 27V DC from the module. Voltage under load will certainly be less than open circuit, so it may not exceed the upper limit of the S280.

Solar Edge P320 optimizer MPPT range is 8 to 48 volts. It should, therefor, begin delivering power earlier in the morning and continue later in the afternoon than the micro inverter would. The later in the afternoon you can continue generating power, the higher the per kWh rate you can earn from the PoCo on net metering.

I can clearly see Enphase producing power outside of the MPPT voltage range. So, I believe MPPT voltage range only applies to MPPT optimized inversion. You still get power outside of the MPPT voltage range but likely at lower efficiency. BTW, I don't see voltage outside of the MPPT voltage range on clear days during this time of the year except before 6am and after 8pm which makes very little difference on total energy produced.

[ButchDeal]

I can clearly see Enphase producing power outside of the MPPT voltage range. So, I believe MPPT voltage range only applies to MPPT optimized inversion. You still get power outside of the MPPT voltage range but likely at lower efficiency. BTW, I don't see voltage outside of the MPPT voltage range on clear days during this time of the year except before 6am and after 8pm which makes very little difference on total energy produced.

No you don't get power outside of the MPPT operating range. The system will stop at the edge of the MPPT range which is not the optimal voltage for some modules. Thus th ineficincies.

[solardreamer]

No you don't get power outside of the MPPT operating range. The system will stop at the edge of the MPPT range which is not the optimal voltage for some modules. Thus th ineficincies.

Looking at my inverter output I see each producing a little power ~1W around 26V which is under the minimum MPPT voltage spec of 27V. The MPPT voltage range is stated as peak power voltage range in the datasheet which seems to imply it's possible to produce less than peak power outside of the voltage range spec.

[ButchDeal]

Looking at my inverter output I see each producing a little power ~1W around 26V which is under the minimum MPPT voltage spec of 27V. The MPPT voltage range is stated as peak power voltage range in the datasheet which seems to imply it's possible to produce less than peak power outside of the voltage range spec.

That is barely powering the inverter and in the error range of the inverter meters. In way we were talking about the MPPT "operating" range . It doesn't operate outside of the operating range.

[Six4KilowWatt]

The max power shouldn't really clip the Enphase. Now there are reasons not to consider Enphase, the big one is that the company is in trouble. However the other solar companies making inverters aren't exactly fortune 500 companies either.

Enphase keeps the electronics on the roof, this is good if you don't want an inverter box out in the open, aesthetically it can be ugly to some. However mostly they are just put somewhere nobody cares to see anyway.

The cost per watt goes down with Enphase if you do the work yourself...get the racking/panels etc...mount all the panels and leave the wiring for the electrician. That is why I like Enphase. It does make it possible for DIY. The systems are rather plug and play.

Permitting process is generally simpler with Enphase. String inverters are less DIY friendly. However if you use Enphase and do the DIY/electrician route, it's going to get you into the payback period much faster. That is why I like Enphase for certain applications, grid tied in particular. Off grid...not so good.

Of course if you do use a regular inverter, then you should absolutely get optimizers as insurance of energy harvest. Clouds happen...there is no such thing as full sun perfection...Optimizers should be considered mandatory.

[ButchDeal]

The cost per watt goes down with Enphase if you do the work yourself...get the racking/panels etc...mount all the panels and leave the wiring for the electrician. That is why I like Enphase. It does make it possible for DIY. The systems are rather plug and play.

This is true of ANY system. DIY reduces costs. No more or less so for enphase.
Any system can be done DIY.

[foo1bar]

The cost per watt goes down with Enphase if you do the work yourself...get the racking/panels etc...mount all the panels and leave the wiring for the electrician. That is why I like Enphase. It does make it possible for DIY. The systems are rather plug and play.

When I was planning 2 years ago I priced out my system using Enphase vs. using Solaredge.
Solaredge was cheaper by a fair amount when I priced everything out.
And not much difference (IMO) in complexity for wiring it.

Permitting process is generally simpler with Enphase.

I disagree.
It's the same process - slight differences in what you have drawn on your plans, but the process is very similar.

String inverters are less DIY friendly.

slightly less.
Solaredge is pretty close to the same though.

However if you use Enphase and do the DIY/electrician route, it's going to get you into the payback period much faster. That is why I like Enphase for certain applications, grid tied in particular.

I don't think pricing has changed significantly in 2 years.
I think if you're DIY'ing it, Solaredge is cheaper than Enphase.
And string inverter (if not having to do rapid shutdown) is cheaper still.
(But string inverter wasn't an option for me due to multiple orientations and shading issues)

[quote]Clouds happen...there is no such thing as full sun perfection...Optimizers should be considered mandatory.
BS.

If there's no shade/obstacles and similar orientation optimizers aren't necessary.
They do provide a number of benefits:
1> shading impact reduction
2> enhance production when dealing with multiple orientations
3> satisfy rapid shutdown requirement
4> provide per-optimizer power production information (usually that means per-PV-module, but not always)
5> very minor increase in production because of mppt per module and modules aren't perfect matches

All nice benefits, BUT there is the downsides:
1> cost
2> extra equipment on roof
3> cost
4> did I mention cost?

Are the extra costs worth it?
IMO yes - for many many installs they are.
BUT when you have a roof that only has 2 faces and it has zero shading it's really difficult to justify.
(I'm on a church committee where we're wrapping up exactly that type of install and the installer did choose solaredge - so he still thought the rapid-shutdown and per-optimizer production info was worth it)

[solardreamer]

That is barely powering the inverter and in the error range of the inverter meters. In way we were talking about the MPPT "operating" range . It doesn't operate outside of the operating range.

That's possible but it does not seem likely. The inverter generates ~2W with voltage in 27-28V which is within the MPPT range. The power drop off against voltage looks fairly linear in the 26 to 28V range. So, it looks like the inverter is still operating outside of the MPPT range but there is just so little sun when voltages are low (in or out of MPPT range) there is just not much power to be generated. It would be interesting to see what kind of power other inverters (micro or regular) with wider MPPT range can generate at low voltages like 26V or below with similar panel. My suspicion is no significant difference.