Review & Comparison

The debate between Optimizers and Micro-Inverters regularly rages in the solar industry, particularly between the two leading products: SolarEdge and Enphase. Over the last few years, I have all but sat on the fence, seeing the advantages and disadvantages of both. Now I’m putting SolarEdge and Enphase head to head.

We decided by somewhat arbitrary means to adopt Enphase rather than SolarEdge last year and have been installing Micro-Inverters throughout Brisbane with over 2000 Enphase Micro-Inverters commissioned to date. But three major changes in the industry have in my opinion brought the argument to an end. There is now a clear winner – at least for the vast majority of systems we install.
Read my update at the bottom of this post for an interesting development!

Three changes in the solar industry

1. Customer requirement changes
   The first change that has happened over that last several years is that we are now installing larger systems than ever before. As the price of solar drops and the prospect of storing excess energy draws closer a typical size system that customers request is “the biggest you can do.” The biggest system we can install in a single-phase home is restricted by Energex to cumulative inverter output of 5kW. According to the Clean Energy Council guidelines, we can oversize that inverter by 33 per cent, allowing us then to install 25x260W panels or 6.5kW.

• This is no problems with Solar Edge’s SE5000 inverter, with a helpful nominal output of 4985W we can install 25x260W panels, or 6500W.
• The new regulation required Enphase Micro Inverter is 230W. With Energex’s 5kW cumulative limitation, the most we can install is 21x230W micro-inverters (4830W). Matching 21 x 260W panels with these inverters gives the customer only 5460W.

One up for SolarEdge.

2. Local regulation changes
   The next industry change affecting inverters is the power factor correction requirement. The requirement introduced by Energex in October 2015 effectively means that inverters are now limited to 0.9 of their maximum output. Compare both systems with 21 panels split east-west:

• On an Enphase system, each panel facing east will be limited by its micro-inverter at about 10 am to 0.9 of its output. While the panels will be wanting to operate near the full 260W, they will be cropped to 207W.
• On a Solar Edge system, the 5.0kW inverter will be limited to 4,5kW. However, at 10 am, while the eastern panels will be cranking – the western panels will just be warming up! At 2 pm, the opposite will occur. The output of the panels on the SolarEdge inverter will hardly ever be limited by the total 4.5kW output of the inverter

That’s two for SolarEdge.

3. The battery revolution
   The third change that has happened in the industry is the imminent battery revolution. While batteries are not yet affordable, inverter manufacturers are bringing out solutions to future-proof their inverter.

• The Enphase solution is a 1.2kWh hour AC coupled battery. The size of this is strikingly token, and the fact that it is AC coupled means it is less efficient. Read my review of the Enphase AC battery.
• The Solar Edge Solution is compatible with the Tesla PowerWall. Case in point if I have ever seen one! Both SolarEdge and the PowerWall work at 350v DC – an efficiency match made in heaven.

A third knockdown blow to Enphase.

The exception

The three points above may not come into play in certain situations. For example in a small shaded cottage, where the customer is looking for a 2.5kW system and therefore not require any significant storage solution. In this instance, the minor pros and cons listed below may come into play.

Other pro’s of SolarEdge

Not meaning to kick my good friend Enphase when he is down, but there are further advantages of SolarEdge.

• There are less moving parts in an optimizer, so it could be argued that they are more reliable on the roof.
• To back up the last point, SolarEdge offer a 12/25-year warranty. Enphase’s warranty is ten years.
• Individual panel monitoring in included with SolarEdge, Enphase ask for an additional $300.

The pro’s of Enphase

As mentioned, Enphase has been good to us. It would be remiss of me not to mention the strong points.

• Proven reliability. At MC Electrical, we have not had a single micro-inverter issue in over 2000 installed in the last 12 months. I cannot personally speak about SolarEdge reliability.
• Safety. It could be argued that having 240V AC run through the roof instead of 350V DC is safer. (However, SolarEdge string cables can easily be powered down by turning off the mains switch.)
• No DC Isolators. DC isolators are traditionally the weakest point of a solar installation – Enphase does not require DC isolators. However, this bad reputation could mainly be put down to sloppy workmanship, poor installation methods, and cheap components in a young industry.
• Consumption monitoring. While SolarEdge has a consumption monitoring option, it is around $700. Consumption monitoring will become an important part of a well-designed solar installation, particularly in the light of the coming Battery Revolution.

Summary

While the fight between Enphase and SolarEdge has until now been a fair contest, Solar Edge now wins the battle with three important points:

1. The ability to oversize the array to 6.5kW
2. The lesser effect of cropping on split orientations.
3. The Tesla PowerWall solution.

While SolarEdge arguably has other minor advantages, so too does Enphase. However, in most instances, the three points mentioned above will make SolarEdge the new choice of Module Level Power Electronics for MC Electrical.

Update

In my quest to always find the better products on the market, I have reviewed the latest offering from Tigo. Read my review of the new Tigo TS4 module. With SMA recently buying into Tigo, it’s a product worth paying attention to!

Second update. I love how more options just keep coming. For a more affordable method of panel optimisation, read my Maxim optimiser review.

Mark Cavanagh