Choosing the right SOLAR PANEL INVERSOR  is very important for the solar energy system. The inverter forms the heart of the system and determines to a large extent the performance. 

Below, I give you tips on choosing the right investor and what you should consider when  buying  an investor.



To design a solar energy system, we first look at the solar panels. The orientation, the slope, the type of solar panels and the number determine the rest of the configuration. 

When that is clear, the investor is selected. Here we look at a number of factors.

Properties of an investor

When choosing an investor, a number of factors or properties of the investor are very important. These determine if the inverter is suitable for your solar panels and what the performance will be:

  • Power of the solar panels in relation to the power of the inverter (insufficient dimensioning).
  • Number of entries in the inverter.
  • Number of MPP followers in the inverter.
  • The price of the investor.
  • The connection to the network (1 or 3 phases).
  • Monitoring options
  • Warranty

Next I will explain more about the different characteristics.

Inadequate sizing inverter

I often get questions about the right investor for the number of solar panels. Many questions refer to ‘insufficient sizing’.

What is the insufficient dimensioning of an inverter?

It is often decided to size the inverter. This simply means that the inverter has less energy than solar panels. This is usually around 90%.


The inverter must match the capacity of the solar panels. Each  solar panel  has a certain capacity, expressed in watt peak. The total of all the solar panels makes the capacity with which we can count for the investor.

Why is an investor often badly sized?

This has a number of reasons.

  1. The power of the solar panels. The  pot nce  maximum solar panels that obtained under conditions of  test  seldom achieved in practice. This is partly due to climate, temperature and radiation. 

On a beautiful summer day, solar panels often only reach 80-85% of their maximum capacity. In the months when capital is relatively low, total returns are the highest. It does not make sense to choose a larger investor for these months.

  1. The effectiveness of the investor. The inverter has a certain  efficiency curve  that generally increases towards maximum efficiency. This means, for example, that the investor has an efficiency of 90% to 10% of its maximum capacity. 

Therefore, it is important to achieve higher yields faster. This is done faster with a relatively small inverter.


  1. Purchase price  An investor with a heavier capacity is more expensive (of the same brand). A heavier investor may also deliver a little more energy several times a year. The question is whether that small additional income exceeds the additional costs.


  1. Starting voltage. In the morning, the investor wakes up and will see if it makes sense to produce energy. Starting voltage is particularly important for this. The  investors  smallest  generally have a lower starting voltage.

Can the panels damage the inverter incorrectly?

People often think that it is wrong for an investor to be too small in relation to solar panels. However, the inverter determines what happens and what the maximum power is.

By adjusting the voltage and current, the power of the solar panels can never be greater than the maximum power of the inverter.

East West

With an east-west (or symmetrical) system on a flat roof, we can even reduce the dimension even more. The different orientations can never work at full power at the same time because the irradiation is different. 

The panels to the east will be full in the morning. Then, the power decreases and the solar panels located in the west begin to operate fully. The graph is flattened so to speak. 

Often, up to 80% can be undersized. All of course depends on the situation.

When the solar panels are placed on a sloping roof with east and west orientation, it is even possible to dimension even more. How much depends on the slope of the roof.

Investor Choice 

Investor manufacturers have a certain number of investors. For example, the range can include an inverter of 1.2 and 3 kilowatts. Which inverter should I choose now if, for example, it has 10 solar panels with a peak of 250 watts?

First, it is advisable to consult another manufacturer that has an inverter that best suits the number of solar panels. If you still have to choose, the largest investor is usually a smart choice. 

An inverter from 2,000 watts to 2,500 watts of solar panels is on the small side. It is certainly possible but it will give some loss.

Number of MPP entries and trackers

Investors have a series of entries. This is 1 to 8 strings for the largest investors. A field of solar panels forms a chain. When the fields are of the same type of solar panel and are on the same slope and orientation, they can be connected in parallel to the inverter. 

This is especially the case with large systems. Are the fields not in the same orientation / slope or are different solar panels used? These must be connected to a separate MPP tracker.

Smaller investors always have an MPP tracker. Starting at 3,000 watts (12 solar panels and more), there are investors with multiple MPP trackers available.

Working with MPP followers is very important. Often, different roof surfaces (for example, in a dormer window and the rest of the roof) are connected to a 1 MPP follower. The inverter will continue to operate normally, but will never reach the maximum performance.

I have many different roof surfaces, and now what?

Microinverters Fortunately, there are also other solutions. The best known are the  microinverters  . These are small inverters that are placed behind the solar panel. 

Each investor has its own MPP tracker. The performance per solar panel is therefore optimal. The disadvantage is that microinverters are relatively expensive. However, for smaller systems (<10 panels) it is not that bad.

Power optimizers. For larger systems with many different roof and / or shade surfaces, power optimizers are a good alternative. 

An energy optimizer is a small box with an MPP tracker. An energy optimizer is installed per solar panel. The difference with the microinverters is that the conversion of energy (direct current to alternating current) is done in a central inverter. However, this is a fairly simple inverter because it does not have an MPP tracker.

1 or 3 phases?

The inverter can be connected to 1 or 3 phases. When is a single-phase or three-phase inverter selected? This depends on a number of factors:

  1. How many solar panels are installed
  2. What is the capacity of the main connection?

1. How many solar panels?

The number of solar panels determines to a large extent the capacity of the investor. Three-phase inverters are available from 4,000 watts (at least 16 solar panels). Therefore, a single-phase inverter is always used among the 16 solar panels.

2. The main connection.

A standard house in the Netherlands generally has one of the following main connections:

  • 1x 35 amps (most used in the period before 1990)
  • 3x 25 amps
  • Otherwise, for example, 1x 25 amps or 1x 40 amps.

The heaviest connections almost never occur because the transmission costs of the network operator are considerably higher for this. 

If you have a heavier connection, it is often worth lighting up. First check if the heavy connection is really necessary and contact the network operator.

Gray area

The gray area is the part between 17 and 23 solar panels. You are very dependent on the main connection. I discuss 2 common options:

1. 1x 35 amps

The maximum power that can be supplied in 1 phase in the Netherlands is 5000 watts. The maximum number of solar panels is therefore +/- 22.

Note: An inverter of 4,600 or 5,000 watts can not be connected to a 3 × 25 amp connection. If you go to 3 phases in the future (for example, to cook), it is advisable to do it before installing the solar panels and choose a three-phase inverter.

If you want more solar panels, you can ask the network administrator to adjust the connection to 3x 25 amps. The transport rate (capacity) remains the same. Take into account additional costs of approximately 200 euros to install and adjust the meter.

2. 3x 25 amps

In principle, a three-phase inverter is the only option if you install more than 16 solar panels. Sometimes several small investors are installed, but this is usually more expensive.

Choosing the inverter is therefore simple 

  1. Up to 16 standard solar panels (+/- 250Wp), one inverter with a maximum of 3600 watts in 1 phase is sufficient.
  2. Gray area
  3. From 24 solar panels, a three-phase inverter is required.

Preferred phase 1 or 3

In the gray area, it is often preferred to use a three-phase inverter.

  1. The current is divided into 3 phases. This means that cable losses are lower.
  2. The energy is distributed in 3 phases. This increases own consumption because the consumption in the home is also divided into 3 phases.
  3. Normally, electricity is also manufactured in 3 phases by large power plants. Therefore, network operators prefer 3 phases because this is more stable for the network.

You may be interested in reading about the dimensions of solar panels

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