In a home solar installation, the inverter plays the critical role of turning the direct current from the solar panels into alternating current that the house can use.
Broadly speaking, there are three types of inverter systems: microinverters, string inverters, and power optimizers. There are pros and cons to each of these, and situations where one type is more appropriate than another. While a quality solar installer will answer all of your questions about why they recommend a particular inverter, it’s always a good idea to have as much knowledge as possible so that you can ask intelligent questions.
You can read our guide to solar inverters to learn about the different choices. No matter which installers you end up getting quotes from, you’ll almost certainly get at least one proposal based on inverters from either Enphase or SolarEdge.
This is because these two companies collectively now own 80% of the residential solar inverter market. That’s a huge chunk of market share, so if you’re thinking about going solar, upgrading an existing system, or replacing a failed inverter, it’s a good idea to get familiar with the product lineups of these two companies.
Enphase focuses on microinverters, and does not have any string inverters in their product lineup. With a microinverter-based system, every solar panel is coupled with one small inverter that is mounted on the back of the panel. This means that the DC-to-AC conversion happens right at the back of the panel, so the unit must be durable to withstand the outdoor elements for a few decades.
The latest Enphase microinverters are the IQ 7 Series. They improve on the previous IQ 6 Series with an increased maximum output power, making the IQ 7 Series suitable for pairing with very high efficiency solar panels (rated at 400 watts or more) that are becoming commonplace in home solar installations. (If you’re going with lower efficiency budget panels, you can save money by choosing the previous generation IQ 6 Series.)
With the IQ 7 Series, there are three models to choose from: the IQ 7, 7+, and 7X. The main difference between these models is the input and output power. For lower power panels, the IQ 7 will suffice. If you’re using larger panels with higher cell counts (such as 72 cell panels that are common in commercial and utility installations), you will need to move up to the IQ 7+ or 7X.
SolarEdge offers central inverters that pair with power optimizers. (SolarEdge does not offer a traditional standalone string inverter.) Their inverter for residential use is the single phase HD-Wave inverter. There is also a three phase HD-Wave, but that is for commercial use. (Homes in the United States almost never have three phase power.)
With the SolarEdge system, there is a central inverter that is installed in your basement, garage, or on an outdoor wall at ground level. It handles the DC-to-AC conversion for all the panels in the array.
Power optimizers are an add-on that improves the efficiency of the system, especially in situations where some of the solar panels experience shade for part of the day. As with microinverters, there is a power optimizer unit that is bolted onto the back of each solar panel. The optimizers allow the system to handle shading situations better than a string inverter. It also gives you panel-level monitoring.
From a technical point of view, a power optimizer is a maximum power point tracker. An MPPT unit allows an inverter to better deal with partial shading, a situation that could cause the entire array to lose power generation if not compensated for. While a conventional string inverter might have 1 to 3 internal MPPT units, with a power optimizer system there is one MPPT per solar panel. This allows the solar system to get maximum electricity generation in partial shading situations.
One of the key metrics for any solar system is efficiency. This refers to the amount of light that is converted into electricity. With higher efficiency, you can generate more electricity with fewer solar panels.
While solar panel efficiency is something that manufacturers feature prominently, inverter efficiency is also important. This refers to the amount of power loss that occurs within the unit during the DC-to-AC power conversion.
Fortunately, inverter efficiency isn’t much of a deciding factor these days. The majority of solar inverters that you will find on the market these days have an efficiency better than 95%, and some have 99% efficiency. This means that only 1% of the incoming electricity will be lost as heat during the DC-to-AC conversion.
With the SolarEdge system, you have two components to look at: the central inverter, which lists 99% efficiency, and the power optimizer, which lists 99.5% efficiency. The total system efficiency is these two numbers multiplied.
The Enphase IQ 7 series is slightly worse at 97% efficiency, but this is not quite an apples-to-apples comparison. Even though SolarEdge’s power optimizers do help the system perform better in partial shade, microinverters are still a superior system when it comes to handling shade and complicated rooftop layouts. Because of this, the overall system efficiency of a microinverter-based system will still usually be a little better than one based on power optimizers.
Enphase microinverters have a 25 year product warranty, which is the longest in the industry. While SolarEdge power optimizers also have a 25 year warranty, the central inverter comes with only a 12 year warranty. SolarEdge offers 20 and 25 year warranty extensions, but for an added cost.
The warranties for both companies cover product failures, but do not include installation labor. For both the SolarEdge and Enphase systems, this is why having a 25 year warranty is important. While it’s relatively simple to replace a wall-mounted central inverter, much more labor is required to replace a defective microinverter or power optimizer that is attached to a solar panel.
With any product, the length of a warranty gives a consumer a good idea of how long they can approximately expect a product to last. Previous versions of Enphase microinverters came with only 15 year warranties, and also were notoriously plagued by reliability problems, something that Enphase has basically admitted to.
Since then, Enphase has been working on improving product quality and increased their product warranty to 25 years. It’s been several generations since the problematic M190 and M210 product series, and from what I’ve heard anecdotally in the industry, the reliability of the current generation of Enphase products is very good.
SolarEdge also provides a 25 year warranty with their power optimizers. While a power optimizer is also mounted onto a solar panel and has to withstand the outdoor elements for a couple decades, it performs fewer functions than a microinverter. Theoretically, the simpler electronics should mean fewer failures.
The central inverter performs the actual work of turning DC to AC power in a SolarEdge system. Their HD-Wave central inverter comes with a 12 year warranty that you can upgrade for a price. That’s noticeably shorter than the Enphase warranty, but also in line with the warranties offered with string inverters by other companies.
In other words, 12 years is about the expected lifespan of a central inverter. This means that you should expect to replace your inverter at least once during the expected 25 year lifespan of your solar panels. Be sure to include this factor when comparing the price of a string inverter or power optimizer-based system to microinverters.
In general, a microinverter-based system will be the most expensive option, a power optimizer-based system will be somewhat cheaper, and a string inverter will be the least expensive.
In the real world, while it will usually be the case that a string inverter will be your cheapest option, the actual price you pay is significantly influenced by the deal your installer can get from the manufacturer. The effects of local pricing and volume discounts mean that you could get a bid where Enphase is cheaper than SolarEdge.
The long term cost of your system should also be an important factor. While microinverters cost more up front than a string inverter, they’re warrantied to last twice as long. While a 10 or 12 year warranty on a string inverter doesn’t mean that it’s expected to fail after the warranty is over, the length of a warranty should be taken as a pretty good guide about the manufacturer’s confidence in the longevity of their product.
Both Enphase and SolarEdge give you panel-level monitoring that is available from the web or a smartphone app. They’ll tell you how much power you generate in real time, and let you generate reports on how many kilowatt-hours of electricity your system has generated on any day, week, month, or year.
Both systems also let you see how much power each solar panel generates, which is a great feature to help you monitor the health of your system and to know when one panel might be having a problem.
You can preview what this system looks by checking out any of the public systems that are available on the web. While the web portals that SolarEdge and Enphase provide don’t match exactly what their smartphone apps look like, it gives you a good idea of the detail available.
One thing to note: with Enphase, the monitoring system is provided by a separate product called IQ Envoy. It communicates over Wi-Fi or cellular to send data to Enphase servers. If you go with Enphase, be sure to ask your installer about this monitoring functionality and get pricing for the IQ Envoy as a separate line item on your invoice.
With the SolarEdge HD-Wave inverter, the monitoring system is built into the device.
With growing interest in home batteries, especially with planned blackouts in California becoming commonplace, more and more companies are getting into the battery storage market. While the Tesla Powerwall is the current market leader and usually the least expensive option, if you’re thinking about battery storage it’s worth considering the battery offerings from Enphase and SolarEdge.
Both Enphase and SolarEdge pitch their systems as all-in-one solutions that integrate well with their inverters and software.
Enphase offers a 10.1 kWh battery while SolarEdge has partnered with LG Chem to offer their RESU battery, which is also a 10 kWh unit.
Note that both these are smaller than the 14 kWh Tesla Powerwall. The Powerwall is currently being offered for about $0.48 per watt, and is probably cheaper than either the Enphase or SolarEdge options. Still, if you’re thinking about battery storage, it’s worth asking your installer, as they might be able to find you a deal.
If you have a home solar installation with partial shading, solar panels mounted on multiple roof segments, or the desire for panel-level monitoring, then both Enphase and SolarEdge inverters can be a great solution to make sure that you get the maximum electricity out of your solar energy system.
In addition, if you think you might want to expand your system in the future - such as to supply electricity for an electric car - then Enphase microinverters offer better expansion flexibility than either power optimizer or string inverter-based systems.
Which should you choose? While it’s likely that Enphase will cost you slightly more up front (though not necessarily, depending on discounts that your installer can get), if I had to choose between the two, I would go with Enphase.
The reason comes down to reliability. While Enphase products have had reliability issues in the past, several product iterations have occurred since then, and the general “word on the street” from installers is that there are fewer in-field replacements and dead-on-arrival units with the latest Enphase IQ 7 product lineup. In addition, Enphase has done a good job on the customer side by offering their upgrade program to owners with early generation microinverters that suffered reliability issues. Finally, Enphase inverters come with a full 25 year warranty.
SolarEdge power optimizers can also be a good choice for tricky rooftops with shading issues, but there are some reliability concerns with their latest products. Because it’s a public company, these issues are discussed in the open. In a recent earnings call, the Acting SolarEdge CEO Zvi Lando admitted that the company has been experiencing an increased number of warranty claims on their single phase inverter series (the type used for home installations).
...in recent months, we experienced an increased number of single phase inverter failures and heightened call center activity. This was due to a combination of two reasons. First, releasing new products and capability is typically characterized by an initial period of stabilization until manufacturing processes are fully mature. Second, during this period due to our growth in market share and increased shipments, there was a significant increase of new installers and accounts using our technology for the first time, and there is a short learning curve for them as well.
To translate Lando’s first point, their power optimizer product is relatively new and they’re still working out the bugs. On the second point, he seems to be levelling some blame at installers, possibly suggesting that some failures are due to poor installation practices rather than a fault of the product itself.
Whatever the case, the product failures are real, and have been mentioned in earnings calls in both 2018 and 2019.
Even though product failures are covered by warranty, the labor cost of a replacement isn’t covered by warranty. It’s an expense you definitely want to avoid.
Finally, it should be noted that if your solar panels are being installed on a single flat section of roof and you have no shading issues, your best option might be a string inverter. While a 10 year warranty for a single inverter is typical (meaning that you should plan for at least one replacement during your system’s lifetime), the cost of a string inverter is also considerably cheaper than microinverters or power optimizers. In addition, the labor cost of replacement is lower because you don’t have to go up to the roof to replace components. Read our guide to solar inverters to learn more about this topic.