Microinverters vs. String Inverters: What’s the Difference?

No matter what type of PV system you choose, you will need an inverter. A photovoltaic inverter has 2 functions: it converts the direct current (DC) from the solar panels into alternating current (AC) admissible by your house and optimizes the production of the solar panels.

Choosing the right inverter type, brand, and model is one of the most important decisions you’ll make when setting up your solar system. There are two main types of inverters available today: string inverters and microinverters. Let’s take a closer look at how they differ in form and function.

String Inverters: How Do They Work?

On a String inverter , solar panels are connected in series to one or more inputs. This allows high voltage to be supplied to the inverter inputs and thus allows for better conversion efficiency. Small residential and commercial string inverters (2 to 9 kW) typically have a voltage of 600 (about 10 400W panels in series) to 1000 volts (18 panels in series), while larger commercial systems can accept voltages of 1500 volts.

We distinguish 2 conversion stages on the string inverters .

• The first conversion stage couples a DC/DC converter and an algorithm. It is used to maximize the energy production of the string of panels at all times. Indeed, the lighting and temperature conditions vary constantly. To maximize the energy harvest, it is therefore necessary to force the string of panels to work at the voltage that will give the best power at each new operating point. This is called maximum power point tracking (MPPT). Most string inverters have two or three MPPT inputs that work to maximize the system's production. This makes it possible to manage multiple orientations of your solar field or a large number of panels.
• The second conversion stage of the string inverter is strictly speaking the conversion into alternating current (DC/AC conversion). At this stage, the inverter synchronizes with the distribution network and injects a current at the same frequency and voltage as the public network.

Most home solar systems require only one string inverter to handle the energy production from the solar array.

String inverters mount to walls, either indoors or outdoors. Install a string inverter as close as possible to your home's low-voltage switchboard (LVS) for easier installation.

Advantages of string inverters

• For an installation of 10 panels or more, this is the most economical solution
• Higher conversion efficiency – Long life and excellent feedback (string inverters have been around for over 30 years).
• Ideal if your roof or land is well exposed to the sun without shadows
• Richness of ecosystems (easy addition of storage, control, etc.)

Disadvantages of string inverters

• High voltage power supply requires special attention during installation
• A little more complex installation that requires DC protection and AC protection
• Weaker warranties than on some ranges of micro-inverters
• No panel-by-panel performance visualization
• If the inverter fails, you lose all system output until you can repair or replace the inverter.

String inverters with power optimizers

You have the option of choosing a string inverter coupled with power optimizers. These optimizers feature MPPT technology that optimizes the output of each solar panel. The optimized DC power is then fed to a single string inverter that converts the DC power to AC power.

String inverter systems with optimizers require more work to install. However, the power to each panel is optimized, so if one solar panel has a problem, it will not affect the others. You will also be able to monitor your solar panels, so you know how each panel is performing.

Note that these types of systems meet rapid shutdown requirements.

String inverters with optimizers cost more than traditional string inverters, but are less expensive than microinverters. Therefore, if you are looking for a balance between the simplicity of string inverters and the technology of microinverters, you may want to consider this option.

Microinverters: How They Work