SolarEdge inverters: a guide for homeowners
The inverter is perhaps the most important part of a home solar system, and the SolarEdge HD-Wave with power optimizers is one of the market leaders. Here's a guide to help decide if it's a good choice for you.
If you’re getting quotes a home solar system, there’s a very good chance that one of them will specify a SolarEdge inverter.
SolarEdge was the market leader just a few years ago, but its market share has been slipping recently and fallen behind Enphase.
Even so, SolarEdge still has about 40% of the US inverter market share, so there’s good odds that one of your solar proposals will include a SolarEdge inverter system.
I can’t tell you whether SolarEdge, Enphase, or another inverter model is the “best” product for you, but I can give you a simple explanation of the SolarEdge product lineup and its pros and cons. Hopefully, that’ll help you have a knowledgeable conversation with your solar installer.
A super quick overview of solar inverters and power optimizers
Solar panels are magical devices that turn sunlight into electricity - direct current (DC), to be exact. The electric grid is based on alternating current (AC), so in order for the electricity from solar panels to be useful to your home, that DC power needs to be converted to AC. That’s the job of an inverter.
There are different types of inverters that you can learn about in this guide to solar inverters.
The SolarEdge system incorporates power optimizers. A power optimizer is a small component wired into each solar panel. It doesn’t do the DC-to-AC conversion, but does help the inverter to better handle situations where some of the panels in the array are covered with shade.
There’s one optimizer for every panel in the array, and they’re bolted onto the rack behind the panels. Cables carry the DC power down to a central inverter, which will be mounted somewhere near your electric panel. The central inverter (pictured at the top of this article) does the actual DC-to-AC conversion.
How do solar panels connect to a SolarEdge inverter?
In a solar array using a SolarEdge inverter, the panels are connected in series and wired into two or three strings.
Solar panel strings have some limitations, similar to strings of Christmas lights. For example, when one solar panel in a string is shaded, its power output and voltage will drop. That loss of power would normally prevent other solar panels in the same string from functioning, causing the loss of power in just one panel to have a much bigger impact.
It’s the role of power optimizers to minimize this problem. With the addition of power optimizers, unshaded panels in the same string can continue to work even if one or more neighboring panels are shaded. That’s a big advantage that the SolarEdge inverters have over ordinary string inverters.
However, even with the SolarEdge systems, an entire string can shut down if there isn’t enough voltage to power the string. Too few panels, physical damage, shading, or low light can cause a string to shut down prematurely. The minimum number of panels required for a string to function depends on the electrical characteristics of the panels in your array, so ask your installer about this if you’re curious.
Designing a solar panel roof layout with strings
The residential versions of SolarEdge inverters support two or three strings, depending on the size of the inverter.
A string of solar panels is connected by common wiring, which means they must be installed on your roof together. To use our Christmas lights analogy again, if you hang a string of lights on your house, you can’t split the string in half and put some lights on the front of the house and the rest at the back - due to the wire, you have to hang them together.
This design limitation applies to solar panel strings as well. For simple roofs, this won’t have any impact, but it might pose a challenge for your installer if you have a complex roof, such as a hip and valley design.
If your roof isn’t a simple plane, it’s possible that your installer may have some trouble laying out the array in the ideal configuration.
SolarEdge HD-Wave inverter models
There are many SolarEdge inverters, but some are intended for the European or commercial markets. Homeowners will be interested in the single phase HD-Wave. (Three phase power is used in commercial settings.)
Here’s a list of key features that all models share:
- Works with SolarEdge power optimizers
- 99% weighted efficiency
- Can be installed outdoors or indoors
- Panel-level monitoring
- Meets rapid shutdown fire safety requirements
The main specification that differs between models is input and output capacity. Here’s a summary by model:
|Model number||Maximum Input (watts)||Maximum Output (watts)|
An explanation of input and output capacity
The table above lists the input and output capacities of the SolarEdge models, measured in watts at 240 volts.
One thing you may notice is that the specified input capacity exceeds the output capacity by about 55%. Why is that?
The input capacity is meant to be a guide on how many solar panels you can connect to the inverter. This is measured in total watts by the STC rating of the solar panel. If you don’t know what that is, you can read my guide on understanding solar panel specifications. A quick explanation is that the STC rating is the power output of the solar panel under standardized, ideal test conditions.
In practice, your solar panel will probably never achieve its STC rating due to heat, haze, dust, and other factors. As a rough guide, you can expect a panel to generate 75-80% of its STC rating on a bright, sunny day that isn’t too hot.
On top of that, it’s normal for solar arrays to be designed with some intentional inverter clipping. Clipping is a loss of power output because the inverter can’t handle all the electricity that the solar panels are sending.
This might sound like a bad thing, but nearly all solar installations are designed with some clipping in mind. This because the panels might achieve their best output on only a few days of the year. (These will often be clear and cool spring days.) The rest of the time, the inverter may have enough capacity to work without clipping.
The SolarEdge specifications above add up to a DC-to-AC ratio of about 1.55. That might sound high, but in practice this might result in annual losses of maybe 5% due to clipping. (This is highly dependant on the site and local climate, so don’t take that as a hard rule.)
Keep in mind that these figures are the inverter’s maximum input, and your installer may design the system well below that number.
SolarEdge power optimizers
The power optimizers (pictured above) are a required part of the SolarEdge inverter system - it can’t operate without them.
Every panel gets one power optimizer (with the exception of one model intended for commercial installations that can handle two panels), which is mounted on the rack behind each panel.
Here are the key features of the power optimizer:
- Reduces the impact of shading.
- Provides for panel-level monitoring. This means that in your monitoring app, you’ll be able to see the power output of individual panels in the system.
- Provides for rapid shutdown ability to meet mandatory fire protection codes
- 98.8% efficiency
- IP68 waterproof rating
- Maximum input power of 320 watts to 505 watts, depending on the model
- Minimum string length of 6 to 8 panels, depending on the model
- 25 year warranty
SolarEdge power optimizers come with a 25 year warranty, but the HD-Wave inverter has only a standard 12 year warranty. It possible to expand the warranty to 20 or 25 years, but that comes at an extra cost that depends on the inverter size.
Here’s the pricing published by SolarEdge as of 2020:
|Inverter output capacity||20 year warranty||25 year warranty|
|Less than 4 kilowatts||$140||$160|
You can always check the latest pricing at the SolarEdge website.
Is the extra warranty worth it? That’s hard to say: it’s much like deciding whether to purchase an extended warranty for a car or major appliance.
While there have been anecdotal reports of high failure rates of SolarEdge equipment in the past, that’s not something that I’ve heard about lately. That said, inverter failures do happen - they are the component of your solar system that is most likely to fail.
Deciding to upgrade the warranty should be something you discuss with your installer, as they may have insights into the failure rates they’ve experienced with their installations.
Monitoring a SolarEdge system
Like any modern solar inverter, you can monitor the power output of a SolarEdge system in real time. You can do this with either the SolarEdge app or use their website.
Thanks to power optimizers, this includes the ability to see how individual panels are performing. This can help you understand if one panel is having problems, perhaps because it needs to be cleaned.
Using the monitoring app, you can see how much electricity a system generated in a day, or you can go back to see how much was generated in a previous week, month, or year. Some system homeowners make their data public, so you can use the SolarEdge monitoring site to view the data for these public systems.
SolarEdge home hub
In addition to the standard HD-Wave inverter, SolarEdge provides the Energy Hub inverter. It looks identical to their standard inverter, but includes features to support additional components such as the SolarEdge battery, smart switches, and SolarEdge EV Charger.
It’s significantly more expensive than the standard inverter, so unless you need these capabilities - or think you may want to add them in the future - the standard HD-Wave inverter will be the best choice for you.
Which SolarEdge inverter model should you choose?
Unless you think there’s a possibility that you may want to expand your system with more solar panels in the future, most homeowners will want the model with the lowest capacity they need (which includes accepting some clipping).
This is perhaps one of the main disadvantages of choosing a central inverter - regardless of whether it uses power optimizers or not - over microinverters. With microinverters, you can simply add more panels as you need them, because microinverters operate independently of each other.
That’s not the case with a string inverter, including the SolarEdge HD-Wave. If you want to expand your system beyond the capacity of your inverter, you’ll either need to purchase a new inverter or add a second inverter to the system. This will often exceed the cost premium of microinverters.
Since it’s such a common choice that prospective solar customers face, I wrote an article on comparing SolarEdge and Enphase to help you decide.