Alternative to microinverters

[coo1guy]

I'm trying to figure out what it would take to replicate one of these "plug & play" kits if you have standard panels that don't come with built-in microinverters.

What type of inverter do you need between the standard panels and the outdoor outlet to replicate what microinverters do?

Thanks

 

[svetz]

With Microinverters it's all AC off the roof, so it's panel->microinverter->junction (aka, combiner-box)->load center as your drawing shows.

Most building codes will also require Arc Fault protection and Rapid Shutdown. These are usually built into a microinverter, but not necessarily string inverters. The code will also specify breakers and labels, but that's similar regardless of inverter type.

String inverters need a solar charge controller (aka MPPT) and the inverter. How the panels are arranged in series and parallel is very important as it must match the MPPT, see Figuring out how many panels in series and parallel based on your MPPT.


An all-in-one is generally an inverter combined with an MPPT and possibly a battery charger, it may or may not be grid-tied. One big problem with string inverters is that they're usually not scalable, if you want another kW you have to replace it.

If you have shade you'll probably want microinverters or DC optimizers (e.g., Solar Edge) as shade messes up String inverter systems.

Microinverters have a ton of other advantages:

• Available from several different vendors at all price ranges
• More reliable with longer warranties (25 years) than inverters (~5-10 years)
• If one fails you're only out a panel's input until you can get it replaced. Replacement shipping costs are less because they're each small and light.
• Typically they have the highest conversion efficiencies
• They are silent
• They have very low self-consumption (e.g., not running cooling fans)
• Per panel MPPTs will always outperform or equal a String based MPPTs.
• Shade on one panel doesn't cause loss from the rest
• Unlike string inverters, they can handle odd roof geometries where the solar angle is different for multiple panels (solar optimizers (e.g., SolarEdge) can also do this).
• They sit underneath the panel and don't take up additional space (this was important for me as I couldn't fit an inverter under the house due to the building codes, but the rooftop was well above the flood elevation).
• Lightweight, quick, and easy for one person to install, but one per panel means more time overall spent on it
• Typically you can get per-panel diagnostics which makes it much easier to diagnose problems
• Lower voltage off the roof.
• Don't need to do string designs or calculate string voltages/amperages (see Figuring out how many panels in series and parallel based on your MPPT and Microinverter Voltage Rise Design Issue)
• Allows for different panels of different ages to work together without loss, excellent for growth over time
• The RSD and arc-fault is generally built-in

 

[coo1guy]

Thanks

Still in a DIY (and hopefully slightly cheaper) logic, would it be smart to buy microinverters and connect them to standard panels or is there an optimization in the case of panels with built-in microinverters?

 

[DThames]

Thanks

Still in a DIY (and hopefully slightly cheaper) logic, would it be a smart approach to buy microinverters and connect them to standard panels?

Apsystems QS1 Microinverter connected to standard panels.

 

[svetz]

Still in a DIY (and hopefully slightly cheaper) logic, would it be a smart approach to buy microinverters and connect them to standard panels?

Wait 15 minutes for someone to tell you String inverters are better so the holy war can continue.

The problem with microinverters is when you want battery backup. Previously, the only way to do that with microinverters was AC coupling, which jacked up the total system price. As far as I know, Enphase is the only microinverter manufacturer to have a "total" solution, but Enphase is a high-end product with a high-end price.

Ultimately it depends on what you want to do and can afford. Enphase is pretty much plug and play and it's easy to find any issues.
String Inverters have a lot more rules, but you can learn all those rules on these forums and build yourself a sweet system cheaper.

 

[coo1guy]

I'll clearly go the microinverters road based on what I read, especially as I precisely want to avoid adding a battery to my system.

Any preference between these two models?



Thanks

 

[DThames]

I'll clearly go the microinverters road based on what I read, especially as I precisely want to avoid adding a battery to my system.

Any preference between these two models?

View attachment 107292

Thanks

I can't speak of those two offerings but the special cable that connects most micro inverters together is expensive. Look at the cost per connection as part of your decision process. Note the one with the pigtail, you could cut the connector off (bye-bye warranty, but you could) and wire it into a conduit box. The other one, you could not do that.

 

[Ampster]

Any preference between these two models?

I do not know much about either of those. I have used Enphase at several installations since 2015 with good luck.

 

[Turkey Hollow Solar]

Been having good results with APSystems new DS3 units.

 

[DThames]

Been having good results with APSystems new DS3 units.

I got a bit bent out of shape when APSystems wouldn't allow their data collection unit be be commissioned by someone other than their certified person and they wouldn't certify "just anyone", even with their free training. I went back to the vendor that I purchased from and they helped me get the account set up and working. Not DIY friendly at all, but the equipment is great.

 

[newbostonconst]

I have put cord ends on both Enphase IQ7 micros and APSystems QS1 micros and just plugged them into 220 outlets. They work fine. I have laid them "temporarily" in landscaping with mulch around them before they are permanently mounted.....

 

[Herb]

I pulled the trigger 6 years ago on the Enphase IQ PV system with generation and consumption monitoring, and I have to say it's been great, is not a big system, but it generates around 25-30Kw on good days, my bill this month is 6 USD from 160 USD a few years ago during the summer months. I also have 2 battery backup systems, one for running lights and small appliances, and the other one does the mini splits AC units during emergency situations, with a grid tied when the power goes out the system shuts down. You can add battery backup to just about any IQ system from them but the price is way high for me for the capacity you get.

 

[meetyg]

I'll clearly go the microinverters road based on what I read, especially as I precisely want to avoid adding a battery to my system.

Any preference between these two models?

View attachment 107292

Thanks

Both are cheap trash...
I have 2 units of the second type, one failed very quickly. Their main problem is heat: They generate alot of heat, and have very small cooling fins, which don't help much.
I kept mine in an enclosure with 12v fans, in the shade, and they still heated up to the point where I couldn't touch it.
The one that didn't fail would stop production every 15 minutes or so, for about 10 minutes.
This was with only 400w or so of solar.

I don't think the first type is any better.

In the end I got a Deye Sun 2000w microinverter, with 4 MPPT inputs.
It's much better, had been running for almost a year now with no issues.
It also has cloud based monitoring with lots of information, so you can check up on your solar production (although the cloud updates only every 10 minutes or so, but good enough for me).

Yes, the Deye is more expensive, but in the long run, it's worth it (rather than buying one those cheap ones every few months).

 

[Herb]

I agree, reliability is a must, I went with Enphase, precisely for that reason, you get what you pay for. There are still excellent options out there, when I'm not using solar for anything, since I run the main off grid system for just 12 hours a day during hot days here in TX, I hook up a cheap GTI inverter that I've had for over 5 years now, basically run it everyday, and it pumps ac back to the grid, on a daily basis is can do up to 5Kw so it also suplements my daily energy consumption, that and the grid-tied PV system makes more energy than I use so is deposited during the day and used at night if needed.

 

[Turkey Hollow Solar]

I got a bit bent out of shape when APSystems wouldn't allow their data collection unit be be commissioned by someone other than their certified person and they wouldn't certify "just anyone", even with their free training. I went back to the vendor that I purchased from and they helped me get the account set up and working. Not DIY friendly at all, but the equipment is great.

APSystems now has a DIY option that allows both the app and website.

I don't know if it provides full functionality, but it appears to. They have also responded to Tech Support questions.

In my recent experience, I consider APSystems to be DIY friendly!

 

[DThames]

APSystems now has a DIY option that allows both the app and website.

I don't know if it provides full functionality, but it appears to. They have also responded to Tech Support questions.

In my recent experience, I consider APSystems to be DIY friendly!

That is good to hear. I did my install in 2019, so not current with their position.

 

[Herb]

I checked their website, have you checked their prices? I like that Zigbee communication method. The house is mostly on a zigbee network, but I'm pretty sure they use their own frequency. I wonder if I can integrate 6 of those with my current grid tied, it would be the same as what I do with the GTI, but I think 6 of those (1 per 2 panels) would generate a lot more energy than the GTI I'm using now, I would think. The 10 year warranty seems a little short but if the price is right it would be an excellent option IMO.

 

[DThames]

I checked their website, have you checked their prices? I like that Zigbee communication method. The house is mostly on a zigbee network, but I'm pretty sure they use their own frequency. I wonder if I can integrate 6 of those with my current grid tied, it would be the same as what I do with the GTI, but I think 6 of those (1 per 2 panels) would generate a lot more energy than the GTI I'm using now, I would think. The 10 year warranty seems a little short but if the price is right it would be an excellent option IMO.

The QS1 quad units that I have are discontinued. Looks like the DS3 dual unit could be as low as $185. The expense of the AC cables is unwelcome.

 

[Herb]

The QS1 quad units that I have are discontinued. Looks like the DS3 dual unit could be as low as $185. The expense of the AC cables is unwelcome.

I was just watching an installation video, seems like the installation is basically the same for the Enphase Micro inverters. Price-wise you could save on the inverters, compared to the Enphase ones since you can use 2 panels with one dual inverter, but not sure about the cable costs and accessories associated with the setup. I would have to request a quote to see, also the panels I have are not that big and might not be worth the extra expense in my case.

 

[Cyanlite]

Wait 15 minutes for someone to tell you String inverters are better so the holy war can continue.

The problem with microinverters is when you want battery backup. Previously, the only way to do that with microinverters was AC coupling, which jacked up the total system price. As far as I know, Enphase is the only microinverter manufacturer to have a "total" solution, but Enphase is a high-end product with a high-end price.

Ultimately it depends on what you want to do and can afford. Enphase is pretty much plug and play and it's easy to find any issues.
String Inverters have a lot more rules, but you can learn all those rules on these forums and build yourself a sweet system cheaper.

Yep and I'll also add in that if you don't buy their expensive batteries and the grid goes down, the older Enphase system shuts down. If you have the newer IQ8+ microinverters, then you CAN get 30% of your solar power towards a critical loads panel.

With a DC-coupled string inverter system that everybody else here does on this forum, we wouldn't even notice or care if the grid goes down