Enphase Microinverters Updated June 2019
Enphase Microinverters are hands down the best microinverter on the market today. But is a Micro-inverter the right option for your home? This Enphase microinverter review will point out the pros and cons of using Microinverters compared to other inverter and optimiser solutions.
We’ve hardly installed any Enphase microinverters for in the last three years. It’s not because I have anything against Enphase. Enphase is a premium product. But Enphase didn’t work with Sunpower E Series panels Panel, our premium solar panel. Frankly, when pushed to choose, I would choose Sunpower Panels every day. There are other inverter solutions that will work in place of Enphase.
But in June 2019 that changed. We’ve had our first delivery of Sunpower compatible Enphase IQ7+ microinverters – an inverter that can handle the higher voltage of Sunpower panels. Now premium customers can have their cake and eat it too!
So it’s time to revisit Enphase and nut out the Pros and Cons of using a microinverters.
The Pro’s of Enphase Micro-inverters
As mentioned, in the last 3 years we haven’t installed many Enphase Microinverters. However, in 5 years we have installed about 5000 micro’s over in about 77 installations. We’ve had 2 failures. You could say that’s 2 per cent of Jobs which would make it look bad compared to a quality inverter. I would prefer to compare it to SolarEdge. 34% of our SE jobs have had at least one fault. See my SolarEdge Stats here.
I went to the wider industry to ask for help. “Solar Cutters” is a community of solar industry experts with a diverse range of experience and opinions. As you might imagine, it’s hard to get a unanimous opinion from such an online group. I posed the question:
“Enphase Microinverters are ridiculously reliable: True or False?”
The jury is in. the Solar Cutter community agrees that Enphase is certifiably reliable. But there were also other comments made on the forum so read on.
2. Heavy shading
Enphase microinverters are hands down the best solar inverter solution if your shading is extreme. This is because Enphase microinverters work independently of each other. If you have heavy shading and at some times during the day just one or two panels are in the sun, those microinverters will produce power.
SolarEdge in comparison has to have a minimum of 6 panels in the sun to prevent production loss through voltage blocking. If the panel voltage of SolarEdge system voltage does not add up to 360 volts, then the system will shut down entirely. These issues are explained in-depth in my SolarEdge review.
Tigo and Huawei are better than SolarEdge. Because they don’t work on a fixed string voltage they don’t suffer SolarEdges voltage blocking issue. They do however require around three or four panels in the sun in order to get to the minimum operating voltage of the inverter. Read more on my Tigo review and my Huawei inverter Review. If your shade is not too heavy, then I would often recommend Tigo over Enphase.
3. Body corporates
Enphase microinverters are often the best solar inverter solution for body corporate situations.
- They are cost-effective for smaller systems.
- Because they work independently of each other, they work well on small – multi-oriented roofs.
- Because the inverters are on the roof, you only have a comparatively indiscrete box to install on a communal wall or in your unit.
- Because we run AC cable from the roof, the cable run can usually be more discrete and snuck inside wall cavities.
DC power has the potential to arc if the cable is damaged. For this reason, there are strict regulations about where and how we run solar DC cable to avoid potential damage. The DC cable is run in heavy duty conduit the entire length. We cannot install the cable through tight wall cavities to prevent future damaged when you hang family photos on your wall. As a result, solar installations installed to today’s regulations are as safe as any other electrical wiring in your home.
Enphase microinverter, however, eliminate the low voltage DC altogether by changing the Solar DC power at the panel to AC power. AC power does not have nearly the same potential for arcing as DC power, so regulations about how we run the cable are a lot more lax. If you screw through the AC cable of an Enphase solar system, you will simply trip the safety switch at your switchboard.
In case of a fire, Enphse will always be safer. If you turn off the power of a home with a standard string inverter, the cable to your inverter near your switchboard will turn off, but the DC from your inverter to your panels will still be live. WIth enphase systems, when you turn off the power to your home, the cable to your microinverters will turn off – which means the cable to your panels will turn off.
4. Individual panel monitoring
This is why data geeks are attracted to Enphase. Enphase has the ability to monitor the production of every panel individually and pick up things like. But let’s how valuable panel monitoring actually is.
If trees are growing excessively, it could be a good indication of when to cut them back.
- Blown bypass diodes
Every panel has 3 bypass diodes to protect them from the shade. If they activate too often because of severe shade then they may fail and you will lose 1/3 of the production of your panel. We have only ever picked up blown bypass diodes on two cheaper panels we installed around 5 years ago. We’ve also had 2 microinverters fail and around 50 SolarEdge optimisers fail.
- Underperformance from panel degradation
While good in theory, proving that your panel has degraded by 5 per cent more than it should have is very difficult even with individual panel monitoring. This is why it’s important to purchase a quality panel in the first place. For example, avoid Perc Solar panel manufacturers who have independent tests to show they are not susceptible to PERC degradation. If your panel has failed entirely, this would normally pick up without individual panel monitoring.
Installing expensive and complicated technology to monitor the reliability of simple and affordable technology is madness.
The con’s of Enphase microinverters
1. Potential panel clipping
Historically it has been normal industry practice to oversize inverters by 33 per cent, (eg, to put 6.6kW of panels on a 5kW inverter). This means at lunchtime when the panels want to produce at their maximum, your 6.6kW of panels will be clipped to 5kW total. The practice of oversizing your inverter to 33 per cent only became common because there was not better option. Energex, like most other Electricity distributors, used to state that if you had a single phase home, the largest inverter you could install was 5kW. Other regulations (CEC) stated that the total panel capacity cannot be larger than 133 per cent of the inverter size. That’s why a 6.6kW system on a standard house used to be a cookie cutter solution.
However, in Qld, regulations and a wider range of solar products are making the practice of oversizing less common. Instead, customers are often choosing to pay a small premium and install a larger single phase inverter to avoid lunchtime power clipping.
For example, today it is common practice to put 9kW of panels on an 8.2 kW inverter. Although we have still oversized the inverter by about 12%, the panels may never want to produce more than 8.2kW of power at the same time. This is what I call “inverter capacity sharing”.
2. Inverter capacity sharing
Inverter capacity sharing occurs when a string inverter is connected to solar panels on multiple roof orientations. For example, if 3.3kW of panels on the eastern roof are performing at their maximum at 10 am in the morning, the other 3.3kW of panels on the west will not be performing as well. At 10 am, the combined panel output may only reach 6kW. The same “capacity sharing” happens throughout the day, and the inverter will rarely limit the output of any individual panel.
Enphase is different. Because microinverters use only one inverter per panel, Enphase can’t “capacity share” like string inverters can. Instead, each panel is always limited to the output of that inverter. So to reduce inverter clipping, it’s best not to install a panel that is anywhere near 33 per cent bigger than the output of your Enphase microinverter. We recommend a maximum of 10 to 15 per cent oversizing to minimising panel clipping. This will marginally increase the cost of your Enphase system, but it may significantly increase your solar production.
The graph below compares the peak output capacity of the three Enphase micro-inverter models available and show the recommended maximum panel size to prevent significant power clipping. Note this value is peak output. Continuous output is 5 or 10 watts less.
|Enphase Micro Inverter model||Peak output||10% oversized panel (recommended)||15% oversized panel (borderline)||30% oversized panel (not recommended)|
|Enphase IQ 7||250 W||275W||287 W||325W|
|Enphase IQ 7+||295 W||324 W||339W||383W|
|Enphase IQ 7X||320 W||352W||368||416W|
- Common panel sizes now start at 300W. The IQ7 is a bad choice if you want to maximise production.
- The IQ7+ is suitable for 300 to 330W panels.
- The IQ 7 plus is designed for higher voltage panels: SunPower 350W and 360W panels.
Oversizing is an issue easily solved by ensuring your Enphase microinverter is not too small for the panel you choose. A potential problem that can’t as easily be solved is voltage rise.
3. Voltage rise
Voltage rise is sometimes a significant electricity grid issue that can make your solar system turn off in the middle of the day. It’s a fairly complex issue explained in detail in this post. If you have potential voltage rise issues, we’ll need to minimise voltage rise by minimising the length of the AC cable run and maximise the size of the AC cable.
If you have potential voltage rise issues, we’ll need to minimise voltage rise by minimising the length of the AC cable run and maximise the size of the AC cable.
If you install a string inverter like Fronius, this is simple. We install your inverter next to the switchboard and use 10mm cables. In this situation, we might only contribute 0.2% to voltage rise.
If, however, you choose Enphase, we’ll need to run longer AC cables to your roof, and run small Enphase AC cables to every panel. On a high set complex roof, it may not be feasible to minimise the voltage rise on an Enphase system below 1%.
Not every Enphase system will have a voltage rise problem, but if you are looking for the best solar inverter solution, it is a problem worth considering.
5. Battery compatibility
First, let me say that batteries on your solar system are a bad financial decision in most situations. The price off batteries is going up rather than down. The reliability of batteries is not getting any better. When you think of batteries, think of a distant future possibility.
The problem with Enphase is you are locked into an AC coupled battery solution. I’m not saying this is necessarily bad. For the few batteries we sell, it’s always Tesla, which is an AC couple solution.
With Enphase, your solar panels produce DC and this power is inverted to AC power on the roof. If you want to charge a battery, you have to invert this power back to DC to charge the battery, then the battery has to invert it back to AC so you can use the stored energy in your home.
4. Multiple failures points
It’s almost incongruous to say that failure are a week point of Enphase. Enphase has proven to the industry they are ridiculously reliable.
But it’s unrealistic to put power electronics behind every panel on a hot roof and expect nothing to ever go wrong. If micros start to fail, the effort to replace one is much more than replacing a string inverter next to your switchboard. If we get back onto your roof in 10 years time it likely to be extremely difficult to remove the nuts and bolts that hold your panels on your roof. Replacung a string inverter in your garage will be much more simple.
We generally only recommend Enphase (or any type of optimiser) in shaded situations and complicated roofs. Whenever you can, K.I.S.S:
Keep It Simple Stupid!
Enphase Micro-inverters have proven so far to the industry that they are a reliable solution. If you live in an area with extreme shade, we recommend using Enphase microinverters because they work independently of each other. Because of the flexibility of Enphase microinverters and the less intrusive installation methods, Enphase works well in townhouse and body corporate situations. However if you choose to go Enphase, be sure your panel isn’t too much bigger than the Micro-inverters output – otherwise, you will limit your production. Also, because Enphase usually contributes more to voltage rise than string inverters, you’ll want to ensure voltage rise is not a concern for your home. Finally, putting power electronics on your roof should be a last resort – string inverters will be much better for future serviceability.