SolarEdge Inverter and Optimiser Review

Having installed over 45 MWp (5,500 systems) of the stuff over 6 years, we thought it would be good to put our experiences and thoughts down on paper and provide you with a SolarEdge review.

What makes a good solar inverter?

When we first started supplying and installing solar 10 years ago, the differences between inverters were quite substantial. Some could be installed outside, some couldn’t; conversion efficiencies ranged from 92% to 97% and most inverters had a transformer in them and were quite heavy to lift – how times have changed!

These days your standard string inverters are nearly identical in terms of the claimed feature set. If you took the logo off the top of the spec sheet and sat them side by side you’d be hard pushed to tell the inverters apart. Under the hood however it’s a very different story, and we know from experience that inverters have vastly different build qualities, leading to variable reliability and performance between brands.

Measuring reliability is a highly subjective undertaking and its nearly impossible to get accurate numbers out of manufacturers – they all say their failure rate is less than 1%! Industry veterans also have vastly differing views about what makes a good, reliable inverter and it amazes us how the fantastic experience of one installer can be equalled by the horrible experience of another.

Support from the manufacturer is key

We have had good and bad experiences with nearly all the major inverter brands at some point in that 10 years. However, the most notable aspect is how well the manufacturer supported us when something went wrong. SolarEdge, hands down, are one of the better companies we have dealt with. Their support is one of the reasons we keep supplying their products to our valuable customers and we know, that no matter what the issue, SolarEdge strives to resolve problems promptly and efficiently. That’s one of the reasons we give a positive SolarEdge review.

While support is the number one factor we consider, there are lots of other things we assess when choosing what products to offer our customers (in order of importance):

1. Technical support
2. Safety
3. Reliability, longevity and quality – these all sort of go together
4. Flexibility of the product i.e. the ability to add a battery or connect a hot water system later
5. Financial stability of the manufacturer
6. Commitment to research and development – how progressive is the manufacturer and are they investing heavily in innovation
7. Price (note this one comes last for us)

No manufacturer gets a perfect score, but the best ones get very close and SolarEdge is certainly one manufacturer that does this. This is particularly evident in the areas of flexibility, R&D, safety and support.

Module Level Power Electronics

SolarEdge is a little different to the rest in that uses Module Level Power Electronics (MLPE) to optimise the production of your Solar PV system. This is probably worthy of a blog post itself, but we will try and break down in simple terms what MLPE does for you and how this differs from your typical string inverter setups.

A typical solar panel contains a group of cells (60 or 120) connected in strings to a junction box mounted at the back of the panel. The junction box holds several bypass diodes which turns parts of the panel off if they are affected by shade. This isolates the effect of the shade to a small part of the panel but unfortunately, in standard solar setups, there is a flow-on effect to the rest of the panels in the system that reduces the overall performance of your solar system beyond just the effect of the shade on one panel.

Standard string inverters minimise the impact of shade by having two Maximum Power Point Trackers (MPPTs) in the inverter. These MPPTs are continually working throughout the day to strike a balance between voltage and current to maximise the amount of power produced. If there is shade on one or two panels then it does its best to keep the power on that string as high as possible. Most string inverters have 2 of these MPPTs, so if there is shade on an east facing panel in the morning it can be totally isolated from the panels facing north that are in full sun.

Introducing the power optimiser

SolarEdge takes an entirely different approach to this problem by installing a little box called a power optimiser at the back of each panel. These power optimisers mean that rather than being restricted to 2 MPPTs you effectively have an MPPT in the back of every panel, which means each panel produces its maximum power and you get more energy out of your solar system.

In addition to having the MPPT in the back of each panel, these module level power optimisers provide a raft of additional benefits:

• Higher system output – optimiser technology not only improves system output, whether partially shaded or not, it also mitigates against panel power losses arising from heat, soiling, production variation or panel ageing.
• Module level shutdown – when you turn the inverter off the voltage coming from the panels and DC wiring drops down to a safe level (1-volt x the number of panels) rather than the 400V-500V coming from the roof of a typical solar system.
• Panel level monitoring – you can see what each panel is doing, and this allows you to track the performance over time – which is essential if you ever have a performance warranty problem down the track.
• Single String Design – SolarEdge’s new design capabilities allow for a whopping 6.66kW of panels to be installed on one long string on its inverter up to 5kW. This not only reduces the number of other components you need on the roof such as DC isolators, it allows for improved capabilities to mitigate against power losses from shading, multiple orientations or soiling.
• Installation flexibility – you can add any type of panel you like (with some exceptions) in practice across several different orientations and it’s easy to swap panels out for a new model if you have issues down the track (the panel specs don’t have to match). This also allows you to expand the system in the future, which may be necessary when a battery is connected.

In summary, MLPE is in our opinion and in our SolarEdge review a superior approach and we think over time we will see it become the standard for solar panels, whether using power optimisers or some other MPLE variant.

SolarEdge and batteries is a great match

DC coupling is a better option for batteries

There are two methods for transferring electricity from your solar panels to a battery. The first method is AC coupling, where the DC power from your solar panels is converted in AC through the solar inverter before reaching a second inverter that manages the charging and discharging of the battery. And we need to mention that the battery will only charge with DC power, so you actually need to convert the power once again from AC to DC to charge the battery. Every time there is a power conversion, there is a bit of power lost.

The second method is called DC coupling, where the solar panels can charge the battery directly in DC power. The great advantage of this approach is that all the charging happens without converting any of the electricity to AC. This is more efficient, and requires less components to pair your battery to solar, which limits the amount of points of failure in the system.

DC Coupling is also a fantastic way to maximise the size of the system you can install at your house, as most grid connection limitations apply to the AC output of your inverter not the number of solar panels (DC) you install. To explain this in more detail look at the following graph for a system that has a 6kW SolarEdge inverter and 9.99kW of solar panels:

If you look at the green curve, which is the total output of the solar panels , you can see the power peaks well above 6kW. So how is this happening given it’s only a 6kW inverter? Well, quite simply, the excess DC electricity coming from your panels is going straight into the battery (the blue line) meaning the battery is charged more quickly. No conversion to AC (which incurs electrical losses) and no knock back from the local network operator (who mandate an AC limit but have provided us with special dispensation to use a 6kW inverter if we ask nicely).

Two New inverter solutions in early 2021

As of January 2021, SolarEdge has introduced two new inverters on the Australian market.

HD-Wave Genesis

The HD-Wave Genesis combines all of SolarEdge’s traditional benefits with improved pricing and single string design for installations up to 6.66kW – Australia’s most popular system size. With this new technology, up to 6.66 kW of DC solar power can be installed in one string, with only one DC isolator needed for the array. This configuration will require less components and labour to install, which translates to lower costs for our clients. Thanks to an attractive new price point, the HD Wave Genesis is designed to fit any shape of roof, to cope well with shade (as with any SolarEdge inverters), and to offer a cost-competitive option against more basic string inverters.

New Generation three phase inverter

The second product introduced by SolarEdge in 2021 is their new generation three phase inverter. This is a long awaited solution for us and our clients. SolarEdge offered a three phase inverter before 2021, but it was rather hard to design with, and the installation would be labour intensive, with complicated strings configuration. So when designing larger systems on three phase residences, we would install either one or two single phase SolarEdge inverters instead, depending on the house consumption pattern (whether there was big loads in the middle of the day or not). But now, with this new product, only one large three phase inverter is required, and that offers some clear benefits. Number one, installing one inverter instead of two can cut the costs of a large SolarEdge system by a few thousand dollars. Number two, a three phase inverter is less affected by high grid voltage. To explain further, when there is large amount of solar energy export (on a nice and sunny day), the grid voltage can increase in a suburb, and the Australian Standard for Solar Inverters requires an inverter to ramp down its production (or even completely shut down) when the grid voltage is too high. This means that on a nice and sunny day, you might not be able to reap the full benefits of your PV solar system. By having a three phase inverter (instead of a one phase inverter), the voltage rise is spread out on all three phases, and therefore, you are less likely to see your inverter shut down during high voltage period. Furthermore, your solar exports are putting less stress on the grid voltage, as they are also spread out on three phases instead of one. Number three, a three phase inverter is less likely to be struck by an export limit by energy distributors, either in a suburban or rural context. This means that you can benefit from more feed-in tariff credits thanks to larger solar export.

Smart homes, device monitoring and hot water control

One of the other great things about getting yourself a SolarEdge inverter is that you can trick it up with several other little gadgets that reduce your energy bills even further and give you greater visibility and control over power hungry devices in your home. Here are some of the smart energy devices now available.

Smart Energy Hot Water:

This is a wireless controller which automatically diverts surplus PV energy to provide hot water. It is a particularly cost-effective way to store excess solar energy. The great thing about this unit is that it ramps the power up and down depending on how much excess solar you have.

Smart Energy Relay:

A wireless switch that controls various loads such as air-conditioners or hot water heat pumps. This allows you to use more of your solar energy and manage your appliance via your phone.

We anticipate several more Smart Home or Smart Energy products to hit the market from SolarEdge over the coming years. It’s an area that is starting to attract a lot of interest from homeowners wanting to control everything from lights, to the charging of their EV to switching on appliances when its more financially beneficial for them to do so. The nice thing about SolarEdge’s approach here is that all these components are just add-ons, you can install them now or later and other than the component itself and a little ZigBee card that goes in the inverter, there is no more that needs to be done.

Buying solar should be no harder than buying a car

There are so many different pieces that go into a solar system and we feel for people that are looking to buy a system for the first time, it must be daunting! This isn’t like buying a car where you drop down to your local dealer and grab a Hyundai, Toyota or a Lexus, sign up for some finance and walk out the door with the keys – buying solar is a very involved process that requires the average buyer to somehow decide between an array of brands, suppliers and installers and sit the first year of an electrical engineering degree along the way.

As it stands now, a typical solar system comprises of at least 10 different brands of equipment. You might have SunPower for your panels, SolarEdge for your inverter, BYD for your battery, Clenergy for your racking system, Hager for your electrical components, EDMI for you meter…the list goes on. It can be a very confusing and complicated process with a lot of different brands to consider.

Whether the manufacturer you are buying from physically makes all the components or not is irrelevant (Hyundai don’t make all the components for a car I can assure you). What matters here is that when buying one brand you have one company providing your warranty, one company to go back to if you have an issue and you don’t get stuck in limbo between manufacturers pretending an issue is not of their making. Imagine if the glue on your new car door frame started failing and you had to call Bostik to come out and fix it under warranty – it would be very frustrating and quite ridiculous really. SolarEdge are looking to change this experience and while its not quite like buying a car yet, its certainly headed in that direction.

SolarEdge diversifying is a good thing

Several commentators have suggested that perhaps SolarEdge is losing focus on their core product by offering panels, smart home devices and EV chargers but from where we sit as a supplier and installer we think it’s a fantastic move by SolarEdge. By diversifying and offering a wider range of interconnected products they are simplifying the process of buying solar or energy storage for customers and cutting out some of the complexity for suppliers like ourselves that are installing, configuring and supporting the system.

Good on SolarEdge for cutting through the complexity, creating a holistic solution in which all the produces are designed to work together, and diversifying their range to provide an end-to-end solution customers are crying out for. The new inverters with HD-Wave technology are a fantastic little unit and our installers like not breaking their backs lifting the 10kg units onto the wall. We can’t wait to see what SolarEdge announce next!