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MIKE KLEEMAN
Email: [email protected] Cell: 925-334-4959

3 Advantages of Power Optimizers over Microinverters

12/29/2015

14 Comments

 
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 ​Powering your home with solar involves two significant pieces of equipment: Solar Panels which produce electricity in the form of direct current (DC); and an Inverter which converts the DC electricity made by the solar panels into alternating current (AC) which is the type of electricity needed to power your home.

There's 3 types of inverter options available to homeowners today: A central inverter which was the only type of proven inverter readily available to the residential market before 2011. A solar breakthrough was realized around that time when Enphase microinverters came along and offered so many advantages over traditional central inverters. Then a few years ago, a third option started to make some real noise, and I like to call it a 'hybrid' option as it combines the benefits of both central inverters and microinverters. That option is the SolarEdge power optimizer.


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​So what's the difference between microinverters and power optimizers?

Enphase microinverters (about the size of an iPad) are mounted under each solar panel on the roof and directly converts the solar panel's DC current into AC current. Power Optimizers are similar to microinverters in that they also are mounted under each panel and perform maximum power point tracking, but they do not convert DC electricity into AC on the roof. The SolarEdge power optimizers go a step further, essentially ‘optimizing’ the voltage and current running through the solar panels to harvest the maximum level of power out of each panel and sends that power to a central inverter which does the hard work of converting the optimized DC current into AC electricity.
 
Both products are similar and offer significant advantages over using a central string inverter:
  • 25 year warranty 
  • Higher efficiency means more power
  • Design flexibility enabling the use of multiple roof slopes, tilt angles and azimuths
  • Panel-by-panel monitoring
  • Both mitigate power loss due to partial shading from trees and obstructions
 
So which should you choose for your home? Both are great options and I recommend choosing one or the other over using just a central inverter. But I can specifically think of 3 Reasons you should choose Power Optimizers over Microinverters: Reliability. Higher Energy Production. Lower Cost. 

1. RELIABILITY
One advantage power optimizers have over microinverters is the issue of HEAT. The DC to AC conversion within a microinverter dissipates heat. We all know the hotter anything gets, the less efficient it becomes. Power optimizers have an advantage over microinverters since the heat generated at the conversion process is done at the central inverter which is usually located inside a garage or outside on a wall near your main electrical panel out of the direct sunlight. The inverter part of your solar is the nuts and bolts component, the ‘moving parts’ of your solar system. Having that moving part of your solar system multiplied for every solar panel on your roof I believe makes your solar system less reliable. Power optimizers need only half the amount of 'moving parts' inside a microinverter. Multiple microinverters tasked with DC to AC conversion year after year and more specifically during summer heat waves I think results in a higher risk of failure. Thankfully both the Enphase and SolarEdge product warranties are quite long at 25 years. 
A disadvantage with microinverters is their risk of ‘power clipping’. Enphase’s largest sized residential microinverter is its M250 model which refers to its ability to produce a maximum 250w AC output from each solar panel when connected to the microinverter. Unfortunately this limits your choice of brand, type and size of the solar panel you can effectively pair with an Enphase system. Want a 72 cell solar panel? Sorry, not compatible. Choose a solar panel with an output greater than 250w AC, and you run the risk of clipping the top off your solar panel’s production at 250w AC. On the pairing recommendation of Enphase's website it denotes that the M250 can be paired with solar panels with ratings up 310w DC.

(UPDATE 1/5/2017 Enphase now denotes the M250 can be paried with solar panels rated up to 350w. This in my opinion is highly inadvisable) 

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Unfortunately, this is a bit of an overstatement. I’ve installed a handful of solar systems using Enphase M250’s with solar panels sized between 285w- 300w DC that have been negatively been affected by power clipping.
So far in my career I've installed slightly more Enphase systems than SolarEdge, and both are exceptional upgrades to the stand alone central inverter. I can count on two hands how many SolarEdge systems I’ve had issues with that involved some form of maintenance or replacement. The majority of those involved replacing the inverter only, and had nothing to do with the power optimizers. That’s why I love the extended 25 year warranty SolarEdge provides for its central inverter to mirror its 25 year power optimizer warranty. On the flip side of that coin I’ve had 3 times the amount of service calls involving Enphase, all of which required troubleshooting the Enphase monitoring system or replacing faulty microinverters. And let me tell you, it’s a lot easier to replace a defective wall mounted central inverter at ground level than it is to replace a microinverter on the roof. Why does it seem that every time a microinverter goes out it happens to be smack dab in the middle of the solar array? It’s never a microinverter on the perimeter, so we have to temporarily lift and set aside 4-6 panels just so we can reach the one panel in the middle with the faulty microinverter. Frustrating!
 
2. HIGHER ENERGY PRODUCTION
Currently, the peak efficiency of an Enphase microinverter is 96.5%. The peak efficiency of SolarEdge power optimizers is 99.5%. Remember though, the SolarEdge system is a hybrid that adds the central inverter component. That central inverter operates at 97.6% efficiency. So with a little math we find that a 99.5% peak power optimizer efficiency multiplied by 97.6% central inverter efficiency equals a peak efficiency of 97.1% with SolarEdge compared to 96.5% with Enphase. That may not seem like a big difference at first glance, but it adds up day by day, year over year. Truth be told, there are those that state Enphase may produce a higher energy yield over SolarEdge, but they’ll never back it up with an accurate apples to apples comparison. Here's a side by side case study that proves just how much SolarEdge Power Optimizers will outproduce Enphase Microinverters.
When a solar panel is shaded from a tree, chimney or a cloud in the sky during the course of a day, its voltage drops. At night, the voltage drops to zero obviously until the sun comes up the next day. To capture power produced by a solar panel, your system is limited by the minimum voltage required by the inverter. The lower the minimum voltage, the greater the amount of energy that can be harvested. A central inverter usually requires a minimum system voltage over of 125v. An Enphase microinverter requires a minimum voltage of 22v. The SolarEdge power optimizers start tracking at only 5v. This means they’ll produce more power in shaded conditions and kick on earlier in the morning thus producing more power as the sun comes up.
 
3. LOWER COST
I know it’s hard to believe. “So what you’re telling me Mike is that power optimizers are more reliable and produce more power than microinverters but cost less?” In a word: YES. A microinverter system is comprised of sophisticated monitoring parts, components and AC trunk cabling not required by SolarEdge. However there is no central inverter to install like with the SolarEdge system, true. On the surface, adding a central inverter to the system sounds like it should cost so much more but it doesn’t. A microinverter is about 2 ½ to 3 times the cost of a power optimizer, and remember it has twice the amount of ‘moving parts’. It’s pretty much like taking a central inverter and dividing it up into 24 smaller inverters over an entire solar system. That’s not cheap. Although the SolarEdge solution requires adding the cost of a central inverter, when you add up all of the microinverter equipment, cabling, monitoring, warranties and the labor to install the Enphase system, the upfront cost to a homeowner is still about 10% more than SolarEdge.
 
So there you have it: Better reliability, more energy produced and a lower cost. When it came down to deciding which upgrade I wanted for my home’s solar system, the choice was easy. I have SolarEdge and you should too.


14 Comments
John
1/5/2016 02:24:42 pm

I prefer SE over enphase for this reason - Consider the number of components in each, number of parts that can fail. Enphase has higher risk of failure, you're looking at over 200 indovidual pieces inside the microinverter compared to what, about 30-40 in the PowerOptmizer. Mulitplied by number of panels. That's a lot more.

Reply
Bob
9/1/2016 07:29:36 am

There's still a massive inverter inside the house with many more higher rated parts that carry a lot more power in the solaredge system. Not to mention if an enphase goes out everything still produces besides the be panel. If a solaredge optimizer goes out, loses communication, or the grid goes out , the whole system goes out

Reply
Mike Kleeman link
11/10/2016 04:00:15 pm

Are you a paid spokesperson for a microinverter firm, or a disgruntled ex-Solar Edge employee?
The inverter is not massive, it's actually quite small. The 'moving' parts of a central inverter are actually less than a microinverter and have lower failure rate. If any one optimizer goes out, the system does not shut off, does not lose communication, And if the grid goes down regardless of whether you have optimizers or microinverters, your entire solar shuts down.

Steve
2/3/2017 06:41:21 pm

That "case study" is very flawed:

1. It compares the output from the best panel of one system against the best panel of another system. That's a major no-no and can introduce a lot of error just from sample variations. The better approach is to take the average of the output from the samples to at least reduce this error. If you do that then the average from the Enphase install is 4.143 and the SE install is 4.81.

2. Next, the "case study" did not adjust for the degradation of the panels based on age. Canadian Solar panels that are 16 months old will suffer output degradation of about 2.72% compared to a brand new panel. This means the Enphase output should be divided by 1/(1-0.0272). So the modified Enphase output is now 4.26.

3. The study did not adjust for reduced output of the Enphase system due to 16 months of soiling. I estimate a 5% reduction is reasonable for the Enphase system. Now the modified output for the Enphase system is 4.26/0.95 = 4.484.

4. I believe the reported SolarEdge output is DC output. That means you have to convert the SE output to AC by multiplying 4.81 by the SolarEdge DC/AC conversion factor of 97.6% to give 4.695.

In conclusion after all the adjustments and corrections, you have 4.484 for Enphase and 4.695 for SolarEdge. This gives SolarEdge a 5% advantage based on these two installations in this case study and not the 13% cited.

Reply
Mike
2/17/2017 04:53:29 pm

Steve, thank you for the great feedback on my analysis. Good points. I'll note however, both systems in my review Iwere washed clean before I read the system production. Also, the rated and warranted panel degradation rate for 16 month old panels is no where near 2.72%. I'm curious where you came up with that number? It's actually less than 1%.

Reply
Bruce Thompson
7/4/2017 03:22:07 pm

I agree with Steve that your 13% advantage is flawed, but so is his 2.72% correction for older panels.
As I ran the calculations with average outputs, I corrected for 0.9333% degradation of Enphase panels that were 16 months older, I applied 2% correction for 255W vs 260W panel nameplate ratings, applied .976% correction to convert SE' reported DC kWh to AC and arrived at 4.14kWh for Enphase vs 4.29kWh for SE, a difference of 3.6% in favor of SE.

Reply
TBD
2/8/2018 07:55:14 am

You are a bad salesman! First, don't say "attack the grid" when you want to promote a renewable energy. Second: several technical flaws in your reasoning. Don't pretend to be what you are not. You are not a tech-guru.

Reply
Lucien Fernandopulle
1/25/2019 08:10:08 pm

Can we use Solar panels only with a common central inverter without optimizers or microinverters for a 200KW system where there is no risk of shading? Please advise.

Reply
Mike
2/12/2020 07:00:41 pm

Just revisted this post of mine from 4 years ago and both interesting and fulfulling to see my initial assumptions and calculations have come to fruition. It is now widely known that Optimizers are slightly more efficienct and push more power over the life of the system.

Reply
Mike
2/12/2020 07:02:42 pm

Joe at Pegsolar.com made a pretty good comparison video a couple years back here:
https://www.youtube.com/watch?v=b5xhBClylHk&feature=youtu.be

Reply
anita link
12/29/2020 11:59:55 pm

Very informative article on the internet. Great work! keep it up.

Reply
Avery B link
1/13/2021 04:14:04 pm

Good readinng your post

Reply
Shyamal Mitra
8/14/2022 07:48:13 pm

I would like to know if all of the reasoning still applies in 2022 as regards power optimizer and microinverters. Are power optimizersstill better than micro inverter as regards total energy output. Have gotten multiple quotes and it seems most venders I still recommending microinverters. Also is it true that optimizers are better in shaded areas.

Reply
Jonathon Pham link
11/11/2022 08:26:38 am

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