Solar panel inverter

Inverters for solar panels, what are they and what do they do?

An inverter is a very important part of your solar power system. But what exactly do they do? Inverters convert the direct current that solar panels generate into usable alternating current (also called grid power) for our home or business. Do your solar panels generate more energy than you use? The surplus of energy that has already been converted into alternating current by an inverter can then be exchanged with the energy supplier. This surplus can be netted. Even if you are not using the energy yourself at the time, you can offset it against the energy that you are drawing from the grid at other times. In fact, you are selling this electricity at the same price as the electricity from the energy supplier.

Several types of inverters

There is an enormous amount of brands and types available. Not only are there different brands on the market, per brand there are also different types. So choosing the right inverter is very important. What is the right one for your solar power system depends on several factors. Efficiency is the most important.

Selection criteria for inverters

The first selection criterion when choosing an inverter is that it must be well matched to the total power (number of panels x the peak power per panel) of your solar power system. Once you have determined this, the choice becomes much easier. Next, the arrangement of the solar panels on the roof is important. In what direction are the solar panels located? At what angle are they positioned? And do certain panels catch shade? If so, in many cases a lighter inverter will suffice. This means that the panels may have a higher peak capacity than he can handle, but that this peak capacity is not achieved given the location and any shadow. A lighter version is then sufficient for your situation. And then the best buy. With many solar panels on the roof, it is common to connect them to multiple inverters.

What do you need to think about when installing?

First of all, an inverter produces its own heat. Make sure it is not in the sun. If it cannot dissipate its heat, the efficiency drops and you shorten its life. Inverters with a transformer also produce noise. Place them in a place where the noise does not disturb you on a sunny day. Almost every edition needs its own group in the fuse box. Also, the old meter is often replaced by a smart meter. Your installer often arranges this with the energy company.

How long does an inverter last?

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Where solar panels have a guaranteed yield of at least 25 years and often function for 30 to 35 years, the inverter is a more critical part of your total system. Assume that in the total lifespan of the solar power system of 30 years you have replaced all inverters at least once. Good inverters come with a 10-year warranty. Technically, a lifespan of around 15 years can be expected.

Solar panel inverter brands

There are several brands on the market. Below you can see some of the various brands:

Logo's omvormer zonnepanelen

Inverter certifications

CE-label

The CE mark is mandatory for electronic devices and therefore also for inverters. CE (Conformité Européenne) means that the product complies with European legislation. The label is mandatory as they fall under the group “Ecodesign for energy-related products”.

TÜV mark

As Germany is one of the leaders in the field of solar energy, the German TÜV certificate is one of the most progressive certificates. The certificate is given to inverters that have passed a test on yield, performance, lifetime and safety.

VDE certification

The VDE quality mark is given if a product meets the strict requirements set by our German neighbors, VDE means ”Verband der Elektrotechnik” and is the German variant for the KEMA quality mark. Almost two thirds of all German electronic products have this mark, which also applies to solar inverters.

IEC hallmark

Inverters must comply with the applicable standards such as the IEC 61727:2004. The IEC (International Electrotechnical Commission) seal of approval is given when it has passed certain tests that conform to the standards for the safety of electrical equipment according to the IEC. European inverters usually do well, but some Asian or American variants sometimes do not have the right certifications.

They are tested for durability, reliability, many weather conditions and the course of the efficiency over the years, among other things.

Inverter solar panel certificates logos

Does shadow on your solar panels play a role?

Inverter and MPP tracker

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It is possible that your panels will be partially shaded during the day because of the influence of surrounding trees or the shadow of an adjacent building, chimney or roof structure. In these cases, it is wise to connect the solar panels that are in the shade at the same time to a separate string in the inverter so that not all the solar panels underperform at the same time. The system is only as strong as its weakest link because the panels are connected in series. Because of that series connection, the inverter sees all the panels on the same string as one large solar panel.

The power output of solar panels depends primarily on the strength of the sun. When individual solar panels in a string are shaded, this leads to a large change in electrical properties. Each solar panel has an individual power point, at which it can emit the highest possible electrical power. This is the so-called Maximum Power Point (MPP). The string now has several solar panels with different maximum power points. The ambient temperature also plays a role. The more the panel is away from the optimal ambient temperature the less the yield.

To improve the efficiency they use an MPP tracker. This ensures that the solar panels are always used at the optimum power point. When the solar panels are controlled in this way, they can make the best possible use of the power available at any time of sunshine.

How do you monitor the yield?

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You can monitor the yield of your solar power system via apps that come with the inverters for free. You install these apps on your PC, tablet or smartphone. Most variants have a built-in WiFi to communicate with the outside world. They send their data to a portal where you can read out (part of) the data with your app. This way you track the yield of your system in real-time and see how much yield you’ve had per day/week/month or year.

Often you can also see the power savings in euros. If you want more detailed information you can log in to the portal where you can find more details about the output of your system. How much CO2 you have already saved and how many KW you have already delivered back to the grid. In the portal you can also see if certain panels are still performing sufficiently. Due to a technical malfunction or dirt, it may be that the yield is not optimal. An intervention is then required. Exactly what you can see in the portal depends on the brand.