Buying the right inverter is crucial for proper and optimal operation of your photovoltaic system. There are a number of things to consider when choosing the right device. In addition to the required power, efficiency and reliability, the type of inverter is also critical. Other factors to consider are grid integration, monitoring capabilities, and environmental impact, while keeping your budget and warranty terms in mind.

What is the role of an inverter?

Inverters play a key role in converting direct current (DC) to household alternating current (AC) used by our electrical systems and appliances. In other words, inverters convert the energy generated from renewable sources such as photovoltaic systems into a suitable and usable form in the first place, making them an indispensable component for harnessing clean energy sources. 

What types of inverters are common?

1. Solar inverter / PV inverter:
Solar inverters or so-called string inverters are characterized in particular by their flexibility. They allow the connection of several solar modules to so-called "strings". This allows the alignment and number of solar modules to be adjusted as required, which is particularly advantageous in irregularly arranged installations. Solar inverters also offer the ability to precisely monitor and optimize the performance of each individual module. This is particularly useful when some modules are affected by shading or other factors, as it does not negatively affect the overall performance of the installation.

2. Battery inverters vs. Hybrid inverters:

In addition to the conversion function typical of inverters, battery and hybrid inverters can also store surplus energy in battery storage units, which enables an independent power supply even in the event of grid failures. Hybrid inverters fulfill the dual function of a normal solar inverter and a battery inverter, while pure battery inverters only charge and discharge the battery. When planning a new PV system with a battery, it is therefore advisable to opt for a hybrid inverter straight away. For existing systems in which a solar power storage system is to be installed, a battery inverter can be used. Hybrid inverters allow operation in so-called island grids, in which you can operate independently of the public power supply (grid independence). We carry hybrid inverters from well-known manufacturers such as SMA, Fronius, Kostal, SolarEdge and Huawei in our product range.

3. Microinverters:
Microinverters (often called module inverters) provide module-level control because they are attached to individual solar modules, thereby providing precise power control. They are ideal for systems with variable shading or modules of different orientations. They are generally used in smaller PV systems of up to eight solar modules, as there are few inverters whose input voltage allows less than 4 modules.

4. Single-phase and three-phase inverters:
Single-phase inverters feed the generated electricity only on one of the three phases common in any household. By using balancing meters, the electricity fed on phase 1 is offset against the other consumptions on the other two phases. A 3-phase inverter, on the other hand, feeds the generated current equally distributed on all three phases. The advantage of a three-phase inverter over a single-phase inverter is that it can supply a higher voltage and therefore a higher power. Single-phase inverters are generally suitable for smaller PV systems up to about 3 kWp, while three-phase inverters are used in larger residential and commercial or industrial systems.

What is Maximum Power Point Tracking (MPPT)?

The Maximum Power Point (MPP) is the product of the current I and the voltage U and changes continuously due to various influencing factors (e.g. depending on temperature, incidence of light). The Maximum Power Point Tracking (MMPT) ensures that your solar system can call up the maximum power at any time and despite external influences. In grid-connected PV systems, MMP tracking is usually handled by the inverter. Many inverters now have more than one MPP tracker installed, which means that the optimal operating point for several strings can be optimized separately.

What has to be considered for the dimensioning? 

Basically, the ratio of the maximum DC power of the inverter to the connected peak power serves as a measure for dimensioning. When planning a PV system, it is often assumed that the power of the inverter must also be equal to the total power of the solar system. In reality, however, inverters often do not necessarily have to be designed as large as the kWp output of the solar system would lead one to assume. In fact, it often makes more sense to choose a smaller inverter to maximize the yield of one's solar system, as the device will operate closer to optimal efficiency. For example, for a system on a roof with an east-west orientation with a system power of 10 kWp, it is possible to use an inverter with a power of 8 kW, since in the morning (east) and in the evening (west) half of the solar panels are oriented towards the sun, and thus no power peaks can be reached at midday, as is the case with systems with a purely south orientation. For a south-facing system in Germany, this value is about 90 percent of the kWp output.

Warranty terms

Warranty periods vary, sometimes greatly, depending on the inverter manufacturer. Some manufacturers offer a warranty of up to 25 years after registration of the device directly with the manufacturer. It is therefore recommended to inform yourself about the warranty conditions of the desired inverter.

Choosing the right inverter

If you need help selecting the right one, call us or use our contact form. We will be happy to advise you and assist you in selecting the right inverter for your application.