There are no special electrical home appliances made specifically for solar system users. That’s why solar energy needs to be converted to the right format (220-240V AC in this case) to be useful.
In a solar power system, this happens at many different scales, but the principle is the same: get electricity from the solar panels and convert this DC to AC, which is the format of electricity used by household and office appliances.
The inverter is the final stage of this process and needs to be efficient and accurate to avoid messing up your cool gear.
Today, we look at the SolarEdge SE25K Inverter (the name could be catchier, we know…) and a generic industry standard 25kW string inverter.
The SolarEdge SE25K is a complete PV system said to be able to produce good quality AC for a much lower cost than similar systems.
From the company’s name, you can guess they concentrate primarily on the manufacturer of electronics to use in solar systems and aim to be cutting ‘edge’. SolarEdge was founded in 2006, making them a relatively new player in the solar system game—but they’re already making waves.
The company have been very actively building their resume and have received many awards for innovation, including the Intersolar Award in 2016 for their HD inverter.
In addition to inverters, SolarEdge manufacture electronic tools for controlling your solar system so that you get the best performance from it. They have what they call the Power Optimizer which is a DC/DC Converter that tracks the maximum power point of the solar panels to increase your system’s overall efficiency.
The Power Optimizer adjusts the current being drawn from the solar panels so that energy is transferred from them to the inverter at the fastest rate, because time is money, of course.
Their products can be connected via the internet using your home WiFi and ethernet cables for remote control of each system, and in this way you will be able to measure the amount of energy that has been generated each day by your system.
Through the SolarEdge Control and Communication Gateway microcontroller, you can log all voltage and power levels of all aspects of your system. We are quite impressed with a monitoring app for the iPhone or any iOS device, so SolarEdge definitely has a more modern approach to solar systems.
The iOS and Android apps are designed to be understood by regular non-tech folk, and SolarEdge must be applauded for this because most companies assume everyone knows what’s up, which we have found to not be true in most cases.
The immersion heater controller, part of the company’s home management range of products, helps to divert any extra electrical energy generated by the solar panels towards heating of water. Usually, more electrical energy gets generated in a day than you need, so this increases the savings you would get by simply diverting energy to where it is needed.
With just basic solar system knowledge, you can optimise the energy flow in your electrical system all through home WiFi and not too many companies can or will provide these features. SolarEdge systems tend to be purchased by experienced solar users who want to avoid the common mistakes of oversizing your system and failing to deal with the long-term effects of uneven aging of solar modules and shading.
On this YouTube channel, you can see a lot of videos of SolarEdge products and their applications.
So far we can see that this company caters to more tech-savvy customers who want to maximise the benefit they get from installing a solar system.
SolarEdge’s popularity is on the rise—they’ve sold 22,700,000 Power Optimizers and 95,000 Inverter units to date, so there is a definite demand for their products. Reviews from customers who have bought these are almost all good and, if you are buying from Australia, consumer law will cover any repairs or replacements, so Aussies are covered!
A good solar system is one which saves you money, simple. Strictly speaking, the inverter converts DC energy to AC, but this SE25K is a complete system that has the solar panels as well as the surrounding electrical circuitry, which includes the inverter.
We will take a look at the features that separate this from the competition.
Longer Strings for an Overall Lower Cost
The SolarEdge SE25K is in a category of inverters known as string inverters. When a string converter is put together, the solar cells are connected in series instead of in parallel, which leads to a higher overall output voltage. The higher the voltage is, the less costly the rest of the system circuitry, known as the Balance of System or BOS, will be.
The table below shows a comparison between the SE25K and an industry-standard system with the same rated power output of 25kW. There is less cable required when installing the SE25K because of the different layout of the SE25K system compared to the traditional industry-standard setup.
|DC cable 1*6mm2||1084m||126m|
|DC cable 1*10mm2||212m||108m|
|DC Isolating kit:
Panels DC Box including main DC breaker and fuse disconnectors for 3 strings. Inverters DC Box including DC disconnector.
|DC Isolating kit:
Panels DC Box including 2X main DC breakers and fuse disconnectors for 6 strings. Inverters DC Box including 2X DC disconnector.
When using line inverters, the current in the solar cell with the least sunlight on it will determine the overall current of the line. Sometimes, when a module is covered by shade, more electrical power can be achieved by diverting the flow of electricity away from this solar module.
The SE25K is chosen by customers who want to get the absolute maximum amount of power flow from their system, which can be achieved through monitoring of the power flow from each solar module.
DC Safety Unit
As a general rule (there are so many in life, unfortunately), the output of a grid-tied inverter should be isolated before connecting this to the grid. Isolation basically means making sure there is no DC current path from the grid to the inverter or vice versa.
Isolation is usually achieved by using an expensive transformer but the SE25K has this covered for you making it a good option for connecting to the grid. When connecting to the grid you can take advantage of the feed-in tariffs which many (clever) people in Australia are doing right now.
Optimization Using Internet Networking
The SE25K is intended for indoor installation, but sometimes if you have an unusual structure to your home, you may not be able to easily create a wired network between this and the PV modules. Also, you may want to monitor and control the operation of your system remotely.
In general, ethernet is faster than wireless internet but places limitations on where you can install the unit. The wireless speeds should be sufficient for any monitoring and control required by the system.
With no knowledge of coding, logs of the system performance can be taken over time and can help in developing a long-term strategy for power optimization if you are keen.
The efficiency of the inverter itself, in the absence of the rest of the components of the system (collectively known as the balance of system or BOS), is 98%, which is up to industry standards. This is achieved through power electronics switching and very little heat is dissipated in the circuitry of the inverter.
This is the maximum efficiency according to the inverter datasheet and realistically the efficiency will be less and gradually decrease as the device becomes older.
An inverter basically converts direct current (DC) into alternating current (AC). The way this is done is by switching the direct current on and off very quickly and filtering all the high frequencies away. The higher the frequencies involved are, the cleaner the AC that is produced, and the HD-Wave technology used to convert the DC to AC separates SolarEdge Inverters from the industry standard.
The AC that comes from the grid meets strict quality requirements and should have almost no distortion at all. Since the inverter is (either partially or fully) replacing electricity from the grid, it should be of similar quality. The filter of the inverter is often very costly and if the size of this can be reduced, the overall cost of the inverter can be greatly reduced.
If you look at the pictures below, the multi-level switching done by the SolarEdge inverter requires less filtration. This is something that is often seen at an academic level and it is very rare to see this being implemented on a large scale because this technique is still relatively new.
SolarEdge multi-level switching
Single-level industry standard switching
|Rated AC Power Output||7000||15000||$25,000.00|
AC Output Voltage Line-to-Line/Line to Neutral (Nominal)
Maximum Continuous Output Current (Per Phase)
|Transformer-less Ungrounded Input||Yes|
|Maximum Input Voltage||900V|
|Maximum Inverter Efficiency||98%|
|Night-time power Consumption||< 2.5||<4|
Rated AC Power Output – This is the maximum amount of power at the output of the generator. The inverter does not generate electrical energy but converts it so the input power to the inverter may be slightly more than this. This determines the maximum number of devices that can be running at one time.
AC Output Voltage – The line-to-line voltage is the voltage between two of the three phases (lines) of a 3-phase system. Line-to-neutral is the voltage across one of your wall sockets, which in Australia is between 220V and 240V.
Maximum Continuous Output Current - Maximum current depends on the resistance of the load connected to the inverter. Exceeding this may result in the death of some of your system’s components.
Transformer-less Ungrounded Input – The input of the SolarEdge does not require a transformer or grounding because this is catered for in its design. This saves on cost and potential headaches in the initial setup of the system.
Maximum Input Voltage - The maximum voltage of a solar system is very unlikely to be exceeded because this is the voltage across all the solar cells combined. This can be calculated and accounted for right at the beginning, unlike the current which depends on his load.
Maximum Inverter Efficiency – The inverter will almost always be the most efficient component of your electrical system. Energy loss can occur during electrical switching and filtration, but active filters have been used for years to reduce the loss of energy at filtration to almost zero. Zero voltage switching is used to prevent loss of energy during switching.
Night-time Power Consumption – This is the amount of energy used by the inverter at night when it remains on. The figures of 2.5W and 4W are too small to even take into consideration when planning the system.
The SE25K is a system designed for the more sophisticated solar customer that wants to get the most out of their system.
Line inverters are made to have a high voltage output from the solar cells, which reduces the cost of the rest of the system.
Simpler line inverter systems, like the traditional inverter system we compared the SE25K with, has less power flow when the solar cells are covered by shade because the solar modules generating less electrical energy decrease the overall generation of the system. This problem is taken care of by the SE25K control system.
The inverter alone is no better than industry standard, but if you have the know-how to set it up correctly (or know someone who knows someone) the whole system will save you money in the long run. Just make sure you take your time with the setup because it will take a tiny bit of time to get it right!
If you want to see how much solar or battery storage could save you over the next 5 years, then take our solar saving calculator quiz below!
Or talk to an Instyle Solar expert about the best solutions for home energy storage or PV-panels.
Otherwise, head back to the solar blog to find even more great educational content.