How do micro-inverters work?
These days everybody wants to invest in solar energy because of the massive money savings enjoyed by producing your own energy, but before investing in a solar power system, there is a lot of basic knowledge you need to catch up on to make sure you are getting the correct system for your needs. One key part of a solar system is micro-inverters. But what are micro-inverters and how do they differ from regular solar inverters?
A micro-inverter acts as a converter from direct current (DC) produced by your solar panels into alternating current (AC) which is usable in your household to power appliances and devices. Regular inverters for solar systems are a single system that converts all direct current produced by your photovoltaic (PV) solar panels into AC power, a micro-inverter set up has a small inverter on each panel that converts the current rather than a single centralized one.
The major advantage of this is each solar panel acts as its own independent energy generation device and is dependent on the rest of the array. With a regular solar system, if one panel is affected for example by partial shading, it affects the whole system because panels are joined as a circuit. This would not be an issue with a micro-inverter setup.
With the shading of a particular module, there won’t be any effect on the efficiency of the other modules. So, in essence, each of the individual panels or modules will work on its own without help from the array.
Most people tend to confuse micro inverter to string inverter as they have the same function, but differ in working principle.
Microinverter – Is a small weatherproof device that is installed behind each solar panel on your roof. As the current produced by each panel is converted from DC to AC separately, greater efficiency of energy harvesting is realized. This is new technology and as such does cost more.
String-inverter – Also known as a central inverter, solar panels are all linked or strung together in a circuit and the collective energy is converted by one large inverter to be used by the owner as AC power. If there is an issue with one of your panels, it weighs on the energy production of the entire system rather than just being isolated to that single panel.
Advantages and disadvantages of micro-inverters
Safety – These are a lot safer than the older setups as DC current (which can be deadly) never leaves the panels. Each panel converts the energy on the spot. A traditional setup with a central inverter would have DC cables running from all the panels into the inverter to convert into AC power all at once. Micro-inverters are much safer for the installer and the resident. A lot less can go wrong.
Ease of installation – Micro-inverters really are a plug-and-play setup. With a traditional solar system, the installer would need to run DC cables and
Efficiency – There are many advantages to enjoy from using micro-inverters.
However, nothing beats the advantage of having more solar power voltage.
Comparing this to the string inverter, since all panel is connected together on the string, the solar power voltage would have to take up the lowest voltage from the connected panels. This isn’t so for the Microinverters that have each panel functioning independently of the other one.
Longevity – Mirco-inverters last a lot longer than a central inverter. They come with a 25-year warranty which matches the warranty given for most solar panels by their manufactures. Central inverters only have a warranty period of 10 years, so chances are you will need to replace it once during the life of your system.
Monitoring – Microinverters come with standard monitoring systems that allow you to keep an eye on their output from the comfort of your sofa via a mobile app. Regular string-inverters require paid extras for monitoring.
Easy system up-sizing – If you were to set up a regular 5kW system with a central inverter, but then wanted to upgrade to 7kw, you would need to replace the inverter to cope with the extra load. With miro-inverters, it’s as easy as just adding the extra panels needed. Easier and cheaper.
Isolation of defective panels – If you had an issue with a single panel, it would not affect the output of the whole system, just that panel using a micro-inverter setup. With a regular string-inverter, one weak link will reduce the overall output of the entire system.
Perfect for partial shade – In some cases, homeowners will have a shaded roof for a part of the day which may affect some panels in the array. With micro-inverters, this would only reduce the output of the affected panels and not compromise the entire system.
Upfront cost – The initial cost of a solar system utilizing micro-inverters will cost more, but with the increased efficiency and warranty life, it is a much better investment over the long term.
Are micro inverters worth the extra money?
In my opinion yes. Although there is a greater upfront cost for the installation, there are so many upsides to having them installed that the extra cost is outweighed all the benefits you enjoy. The biggest advantage is that last twice as long so you will be saving money in the long run.
If you are just installing a solar system to increase the value of a home you are just going to sell up, then maybe you are not too worried about the longevity of the system, but if it were my home, I would want better quality equipment that will go the distance.
The last thing you want to be doing is replacing your inverter after 10 years of use. Considering panels will last 25 years, you are the best matching that with a quality inverter.
Are microinverters more efficient than regular inverters?
In short micro inverters are more efficient than regular ones, but to what degree will depend on a host of factors.
In a straight test with the same size system, same solar panels and light conditions the extra power produced would be marginal. But it is when conditions are not ideal that microinverters are worth their weight in gold.
If your solar panel system were to suffer from partial shading from trees or other fixed objects, the drawdown in power loss is only restricted to the affected panels. This is because with microinverters each pane in the system is producing power independently and sending it to your home.
In the same scenario, a partially shaded solar system would spell disaster for the total output of the system as panels are stringed together in an array and rely on the entire system to be working well to produce good energy. A weak link can bring down the whole system.
Top Micro inverters on the market
Not all inverters are built equally, so you need to read up on what is going to suit your needs best.
Below are some of the best inverters for price, functionality and durability. Of course, there are others that I’m sure we’ve missed, but it is hard to go past some of these great models.
Some of these brands include the following:
Enphase is the most popular manufacturer of microinverter, and they have their headquarters in California. The micro inverter would automatically convert the DC to AC at the site of the inverter instead of having to transfer the electricity into a centralized unit like that of a string inverter. Enphase microinverters also come with a minimum of 15 years’ warranty and a maximum of 25 years’ warranty depending on the model of the system.
Enphase alongside Solar Edge is two of the world’s leading solar inverter manufacturers for both residential purposes and industrial uses.
This is another producer of microinverter and power optimizers. They are part of the SMA solar technology company, a company that has its headquarters in Germany. SMA products are considered to be quite expensive, and this is why they are not really as popular as other microinverter companies like Enphase and Solar Edge.
How many micro inverters do I need for a 5kw solar system?
A 5Kw system is the most popular sized system on the market as it generates about 23kWh of energy which is about the national average of daily energy consumption.
As micron inverters are attached to the underside of each solar panel, the real question is how many solar panels will I need to make up a 5kW solar system?
The amount of solar panels needed to make up a 5kWh system ranges from 16-20 panels. Now if you are thinking well why would I pay for 20 panels when 16 will do?
Well, it all depends on the output of each panel.
Different solar panel manufacturers have different product lines with panels producing different amounts of od power at peak levels.
The average is about 150watts per hour. 5000 Watts (5kW) divided by 250 Watts (panel output) = 20. So you will need 20 x 250w solar panels to make up a 5kWh system.
Each panel will have an inverter attached to 20 microinverters.
So a solar panel with a 315 Watt output will need 16 panels and inverters total to make up the same-sized system. Like anything, the more efficient it is the more and you will probably buy 20 panels cheaper than 16.
Here are some popular solar panels with microinverters built-in
Enphase is one of the forerunners of the micro-inverter industry, and in 2017 they switched it up a gear with the convergence of microinverter in solar panels. However, that was not their first attempt at doing so as they have tried the convergence before that and failed.
But with the success of this innovation Enphase has created a milestone in the inverter world such that more costs can be saved for customers. Since the major issue faced with micro inverter is the expense in both purchasing and management this innovation will look to curb that, and a few extra dollars can be saved in the process.
Another popular micron inverter supplier is Sonnon. This is a german company that has been leading the market for some time. You will pay a little bit more for a Sonnen microinverter, but as they generally are a better make than other Chinese models you will save in the long run.
Do I have to buy solar panel micro inverter combos, or can I mix and match?
You can attach any microinverter brand to any solar panel. Although most solar panel manufacturers so have a line of panels with a built-in micro-inverter, for whatever reason you might decide you want their panel but a different inverter.
You can ask your installer to buy them separately and install them together. They are easy to fit and install.
Author: Ben McInerney is a renewable energy enthusiast with the goal of helping more Australians understand solar systems to make the best choice before they purchase. Having an accredited solar installer in the family helps give Ben access to the correct information, which allows him to break it down and make it easily understandable to the average homeowner.