Enphase Micro-Inverter Review

Enphase Microinverters are hands down the best Microinverters on the market. But is a Microinverter the right option for your home? This Enphase review will kick off with an update – a couple of YouTube videos. In these videos, I show why Enphase isn’t necessarily the shade solution we all thought it was. Below the videos, I explain the pros and cons of Enphase microinverters.

First, and most controversially, watch this video to see my test results showing Fronius working better than Enphase with 15 per cent shade! In short, the advantage that the Fronius inverter has is it makes use of the panel bypass diodes – by bypassing the shaded cell strings. In contrast, Enphase hardly ever engages the bypass diode, so ironically a bit of shade on an Enphase panel can drag the performance of the whole panel down.

In this second video, I show a situation where Enphase can work up to 8 per cent better than Fronius in the shade. In this video, I compare Fronius and Enphase using split cell solar panels, and I shade the width of the bottom of the panels from 12.30 onwards. The results favoured Enphase, but the difference was not as significant as you might think.

 

 

The Pros of Enphase Micro-inverters

1. Reliability in comparison

In the last five years, we have installed about 3200 micros on 156 homes. Half of these systems are over four years old, so they are close to halfway through their ten-year warranty period. To date, we’ve had only six microinverter failures (0.18%) and a few communication issues that I’ll address later.

You could say that 6 out of 156 jobs means about 4% of our Enphase jobs have had a failure. That’s bad compared to a quality string inverter like Fronius. However, that’s not a fair comparison. Enphase’s “decentralized power topology” ensures that if one microinverter fails, you’ll only lose the production of one panel. When a string inverter (like Fronius or SMA) fails, you lose the production of the whole system.

SolarEdge is a fairer comparison. SolarEdge uses both rooftop power electronics (optimisers) and a central point of failure (the SolarEdge Inverter). How does SolarEdge fair for reliability? 34% of our SolarEdge jobs have had at least one fault. 11% of our SolarEdge inverters have failed so far, taking the whole system down. See my SolarEdge Stats here.

At 4% of our Enphase installs with an issue, Enphase in comparison is looking pretty damn good. (Remember it’s only 0.18% of Enphase microinverters that have failed.)

I went to the broader industry to ask for help. “Solar Cutters” is a community of solar industry experts with a diverse range of experience and opinions. 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.

Enphase’s “decentralised power topology”, coupled with its reliability, makes Enphase stand out from any other inverter solution on the market. But inverter reliability is only one part of the equation.

2. Heavy shading

Despite my YouTube videos above, where I show that Enphase isn’t always the shade solution it’s cracked up to be, microinverters are 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. This is explained in-depth in my SolarEdge review.

Tigo and Huawei are also good options for shade. They do however require around three or four panels in the sun to get to the minimum operating voltage of the inverter. Read more on my Tigo review and my Huawei inverter Review. However, if shading is minimal, I prefer to use a couple of Tigo optimisers. As I explain later, the fewer Power Electronics on your roof, the better.

3. Townhouses and units

Enphase microinverters are often the best solar inverter solution for townhouses and unit situations.

• They are cost-effective for smaller systems.
• Because they work independently of each other, they work well on small – multi-oriented roofs.
• You only have an indiscreet box to install on a communal wall or in your unit, keeping that whinging chairman of the body corporate happy.
• Because we run AC cable from the roof, the cable run can usually be more discreet and snuck inside wall cavities. You are welcome, Mr Chairman.

4. Safety

String inverters like Fronius and SMA require DC cables to run from the roof to the inverter. Solar DC power is theoretically dangerous if it’s accidentally damaged. (However Australian solar installation regulations are so strict. Solar DC cables installed to today’s standards are as safe as any other electrical wiring in your home.)

Enphase microinverters, however, reduce that risk even further. Microinverters eliminate the higher DC voltages by changing each solar panel’s extra low-voltage DC power into AC power at the panel level. AC power does not have nearly the same potential for arcing as DC power.

In case of a house fire, Enphase will always be safer. Let’s say you chose a string inverter. When you turn off the main switch of your house, the DC cable from your inverter to your solar panels will still be live. That’s unwanted fuel in a house fire.

If you had chosen an Enphase System instead, when you turn off the power to your home, the cable from your switchboard to your microinverters on the roof will also turn off. Safe as house fires houses.

5. Enphase treats the panel gently

In some ways, this may be my favourite feature of microinverters. With a string system, you can run up to 600 volts and 10 amps through each panel. That’s a lot of energy through a solar panel. While panels are designed to run at 1000 volts, the less stress you can put on a product, the better. If there is shade on part of the panel, the shaded spot will consume energy, and heat up the panel. The panel will quickly engage the bypass diode to prevent heat damaging the cell or back sheet. If this happens frequently, the bypass diode could fail. With a Microinverter, only the voltage of just one panel will run through the panel. Around 40 volts and 10 amps. Will less energy becomes fewer hotspots, and the bypass diode will hardly ever have to engage. This means the bypass diode has less chance of failing. If the bypass diode does fail, it is simple to pick it up with Ephase monitoring.

6. Individual panel monitoring

Data geeks love Enphase. Enphase can monitor the production of every panel individually. But let’s see how valuable panel monitoring is.

• Shading
  If trees are growing excessively, it could be a good indication of when to cut them back.
• Blown bypass diodes
  Every solar panel has three bypass diodes to protect them from the shade. As mentioned above, if they activate too often, then they may fail, and you will lose 1/3 of the production of your panel. We have only ever picked up six blown bypass diodes from the 5000+ panels that we have installed with individual panel monitoring (Enphase, SolarEdge or Tigo). However we’ve had six Enphase microinverters, and 56 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. That’s why it’s essential to purchase a quality panel in the first place.

Installing expensive and complicated power electonics on the roof primarily to monitor the reliability of simple and affordable technology is madness.

The cons of Enphase microinverters

1. Multiple failure points

It’s unrealistic to put power electronics behind every panel on a hot roof and expect nothing ever to go wrong. When microinverters start to fail, the effort to replace one is much more than replacing a string inverter next to your switchboard. In the last five years, we’ve only had four micro failures. We replaced those microinverters under the ten-year warranty. But, if we get back onto your roof after the warranty period, you start paying. It is likely to be extremely difficult to remove the specialised nuts, bolts, and clamps that hold the panels on your roof.[ps2id id=’Enphase Warranty’ target=”/]

Let’s hope it’s easy to identify and access the faulty micro. Ladder up, harness on. Panel clamps may be seized depending on your rail quality and the installer’s finesse. Angle grinders come out. Replacement clamps are impossible to find ten years down the track. Should we open a can of worms and start replacing your rail?
Swapping out a string inverter in your garage would have been much more straightforward.

The end customer can purchase an extended warranty online after installation. However, the extended warranty does not include the cost of labour of fault-finding, removing, transporting or reinstalling the faulty micro.

Here’s how an extended warranty compares to purchasing a product outright.

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Because future maintenance will become problematic and costly, we generally only recommend Enphase (or any rooftop power electronics) where shaded situations and complicated roofs necessitate.

Oh, and in case you missed it: the components that monitor production and reveal any problems you may have with your microinverters over the next 10 years … those parts are only warranted for 5 years.

2. Battery compatibility

When batteries do become financially viable, Enphase will limit your options to an AC-coupled battery solution. The main problem with AC coupling is a regulation problem. In Qld, ACT, parts of NSW and parts of Victoria, we are limited to a maximum of 10kW of inverters on each phase. And the 10 kW limit includes the sum of all the microinverters and the AC-coupled inverter/battery charger.

Effectively this means you can have a large solar system and a small battery, or a small solar system and a big battery. If you had the option to DC-couple, you could have a large solar system and a big battery. But going to Enphase does not give you that option. Read my blog on AC vs DC-coupled batteries.

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. We’ll do this by reducing the length of the AC cable run and increasing 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 the 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 AC cable below 1%.

Not every Enphase system will have a voltage rise problem, but it’s a problem worth considering.

4. Enphase’s Achilles heel

A sign of a good company is how they respond when things go wrong.

Enphase monitoring uses power line communication. The microinverter monitoring is transmitted over the same 240-volt cable that powers your appliances. Powerline communication works perfectly well – until it doesn’t. Noise or electrical disturbances from your household appliances can interfere with this signal, and the monitoring stops working. Which appliances can interfere with your monitoring? The Enphase-noise-troubleshooting guide gives a comprehensive list:

Light switches, dimmers, irons, microwaves, touch lamps, computers, battery chargers, phone chargers, laptops, compact fluoros, battery backup systems, hot water diverters, export limit devices or automatic controllers, switches, power strips, surge diverters, ethernet bridges, heavy motors, water pumps, fridges, power tools and kitchen appliances.

Just about every appliance you own could interfere with Enphase microinverter monitoring. Importantly Enphase is not claiming the offending noises are outside of the relevant Australian Standard on Electromagnetic Compatability (AS: CISPR 14.1:2018). It’s just normal electrical noise that happens from everyday appliances that are screwing up Enphase communications. The problem is an Enphase problem.

As it turns out, the first time we encountered this problem on one of our installs, I was writing this blog. The timing was joyfully serendipitous. Shane, my service manager, was all over it.

“Mark, Enphase has told us we need to buy a specific filter and install it at the customer’s premises in order to fix the noise issue.” Shane told me.

“That’s fine” I replied, “As long as Enphase reimburses us for the parts and labour, it doesn’t bother me”.

“That’s the problem” Shane continued. “Enphase Tech support is telling me they don’t reimburse anything for noise issues.”

I laughed out loud. Enphase wouldn’t be so stupid, would they?

Enphase mans up

The joyful serendipity continued because the same morning, Enphase’s product line manager Andrew Mitchell had arranged to drop into my office for a meeting. I told Andrew that tech support had foolishly suggested that I’d be out of pocket to fix their communications issue. Andrew was upfront:

“I don’t know what to say, Mark. That’s the Enphase policy. Enphase expects the installer to return and install a filter at their own expense. But I get your point, you installed to our installation guidelines and best practice. We really have no excuse.

He was right. They don’t have an excuse. So I got my keyboard warrior hat on and sent a passive-aggressive email to Enphase. It only took a week until Enphase conceded their attitude was wrong. Andrew knew I was working on this blog, so gave me the below statement to share with you.

“As long as the product is installed, operated, handled, and used in accordance with the Quick Install Guide, Power Line Communications failure on a micro inverter is grounds for warranty replacement and Enphase will cover parts and labour up to 10 years.  If Enphase deems that the communications failure is due to environmental noise and not a product failure it reserves the right the remedy the situation with the use of a noise filter.  

That’s good news for installers. My faith in Enphase has been restored.

Enphase has now developed a filter that seems to have solved this issue. Now we don’t have to worry every time our customer buys a new appliance.

In any case, the power line communication problem does not affect solar production. If it can be fixed by installing a filter, it’s not a massive issue. However, it’s not uncommon for Enphase to replace microinverters because of a communication issue that a filter won’t fix. Again, it’s not reasonable to install Power Electronics on a hot roof and expect nothing ever to go wrong.

Oversizing Enphase microinverters

I’ve been on a bandwagon for years, saying you should preferably avoid oversizing microinverters by 33%. String inverters often have panels in multiple orientations so they can “capacity share”. Microinverters can’t capacity share.

Recently I set up a side-by-side comparison on my roof attempting to quantify my argument. I installed 4x 320W panels. Two panels ran on 240W micro inverters (IQ7). The other two were connected to the larger 290W microinverters (IQ7+). I had some concerning anomalies from the IQ7+. I’ll mention those at the end of this section. But for this post, I’ll show my preliminary results which I think are conclusive enough.

 

 

Preliminary results

The blue production curve on the left is the actual production curve of 1 x north-facing 320W panel in mid-September when connected to an IQ7 microinverter. The blue graph was traced from the Enphase portal to Adobe. The red section was extrapolated from the IQ7+ data. The area was calculated with an Adobe plugin.

The IQ7 doesn’t reach the “peak output power” of 250W as per the Enphase spec. Instead, it starts clipping at 245W at about 9 am.

In September the sun is close to 90 degrees to the panels that are tilted at 25 degrees. So clipping will be close to the maximum.

The blue line was the actual production taken from the Enphase portal. The red line is “modelling” what an IQ7+ was reaching at the same time. It peaked at 295W.

The northern panel was clipped by 6.99%. The western panel wasn’t far behind.

This is only data from one perfect spring day. Without trying to predict 12 months of data, including rainy days, winter months, and different orientations, I’m close to admitting defeat. I would guestimate that the annualised losses from clipping would be approximately 2 per cent. If you work that out in dollar value, it’s probably not worth the cost of installing bigger microinverters.

If you are in Brisbane or further away from the equator, as long as your installer doesn’t oversize your microinverter by more than 33% (as per CEC guidelines), your annualised losses will be around 2%. An IQ7 is probably ok on a 320W panel and an IQ7+ can handle 385w panel. Yes, my Humble Pie was delicious.

But I’ll go down swinging with a few points you should consider.

• If you install a 320W panel on an IQ7 micro inverter, don’t complain when your production flatlines in summer.
• And the next time someone suggests that Enphase will yield higher because it handles panel mismatch so well: remind them Enphase can’t “capacity share.” Stick that in your pipe and smoke it.
• Curveball: The anomaly mentioned showed that IQ7+ produces about 5% less than IQ7 at times when clipping does not occur. Enphase has not given me an acceptable answer for this. I’m heading to Silicon Valley mid0October, and I hope to get insights at Enphase HQ.

Conclusion

Enphase microinverters have proven so far to the industry that they are a reliable solution. While they are not necessarily the best shade solution for medium shaded, If you live in an area with extreme shade, we recommend using Enphase microinverters because they allow the panels to 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, rooftop power electronics will eventually fail. When they do, it could be a complicated and costly exercise to replace them. If you choose Enphase, you should also be aware of potential voltage rise issues, and understand that you are locking yourself into an AC-Coupled Battery. Also be aware that if your monitoring is intermittent, noise from an appliance may be causing it, or a microinverter signal could have failed. The good news is, Enphase will now cover the cost of installing a noise filter under warranty. Finally, I was wrong. You can oversize a microinverter by 33 per cent without losing too much yield annually. Just don’t come crying to me when it clips 6.99 per cent of your power on a spring day.