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Last updated: 09 March 2018

Solar PV System: Solar Inverters

What Is a Solar Inverter?

A solar inverter or grid-tied inverter is an essential part of a solar system. The inverter makes the energy usable in the household. Solar panels generate direct current (DC) electricity, which is then converted to alternative current (AC) electricity by the inverter. Efficiency of the inverter is in the 93-95% range, because they use some of the DC power to function.

The efficiency of the inverter can be improved by using a technique called Maximum Power Point Tracking (MPPT). The point of maximum power input varies, depending on the light levels, temperature, shade and specific characteristics of the solar panels.

Types of Inverters

There are two main types of grid-tied inverters, depending on the number of solar panels they are connected to. Central or string inverters are linked to several solar panels, while micro inverters can be linked only to one or three solar panels.

Central Inverter

It is a single device which converts the DC electricity produced by all the the panels linked together. They are the size of a solar panel and are typically installed on a wall indoors. This inverter is most effective when all the solar panels connected to it have the same specifications and work under similar conditions. If not all of the panels have the same orientation or some of them are shaded during the day, it is a good idea to install more inverters in order to increase the efficiency of the solar system, or to install an inverter which has been specifically designed to work with one string of solar panels which operate under different conditions.

Micro Inverter

Micro inverters are installed on the back of each panel. They can be used for solar systems where the solar panels don’t have the same characteristics and don’t work under the same conditions. If one of the panels is damaged or there are some obstacles preventing it to work properly, this doesn’t affect the rest of the solar panels. Those inverters are great for situations where shading is an issue or in case where a central inverter is not compatible with the system.

Read more: What is Solar Panel Efficiency?

In the rest of the post we will take a look at the advantages and disadvantages of both types of inverters. We will also mention some of the situations in which one type is more desirable than the other.

Advantages of Central Inverters

  • They are less expensive than micro inverters.
  • The technology has been present on the market for a long time.
  • They offer more cost effective installation and are easier to replace if needed.
  • If used with smaller solar systems, the operational and maintenance costs are lower than if micro inverters are used.

Disadvantages of Central Inverters

  • They are not optimal in situations where there is shade. If one of the panels is shaded for some period of time, the efficiency of the whole solar system is impaired.
  • They could be dangerous since there is high voltage.
  • They are big and heavy, and usually need to be installed indoors.

Advantages of Micro Inverters

  • Performance of the solar panels in the system is improved and maybe increased with 5-10 per cent over the lifespan of the system.
  • Enhances monitoring the performance of solar panels since each panel can be monitored separately.
  • More reliable system since if one of the inverters fail, it will not affect the rest of the system.
  • Micro inverters are longer lasting than central inverters, most manufacturers give 20 years warrenty.
  • It is easier to increase the size of the solar system by adding more solar panels.

Disadvantages of Micro Inverters

  • They are more expensive than central inverters.
  • More failure points and changing them would be more costly since access to the roof is required.
  • The installation cost is higher than that of central inverters.
  • Relatively new technology and most installers and manufacturers might not be familiar with them, which might be an issue if they need to be replaced or repaired.

Both central and micro inverters have their specific applications and are suitable for different situations. You should consult with your installer and get a recommendation about which inverter would be more suitable for the solar system you require to meet your energy needs.