String Inverters Vs Microinverters Vs Hybrid Inverters

What are the pros and cons of string inverters, micro inverters and hybrid inverters. We delve deeper into the pro's and con's of each to help you decide what may be best for your home setup.

Solar photovoltaic (PV) systems generate direct current (DC) electricity from sunlight and before this energy can power household devices, it needs to be converted into alternating current (AC) – the type of electricity used in homes. Inverters play a pivotal role in this process, and there are several types available, each with distinct advantages and disadvantages.

String Inverters

String inverters are among the most common and cost-effective options for solar installations. They work by connecting multiple solar panels in series, forming a 'string,' and then feeding the combined DC electricity to a single inverter unit.

A string inverter connects a number of panels together to form a string.

Advantages:

Cost-Effective: String inverters are generally more affordable due to their centralised design.

Simple Maintenance: With fewer individual components, they often require less maintenance. They also provide easier access because they are mainly located in the loft space or other easy to access areas.

Efficient in Ideal Conditions: They perform well in situations with minimal shading and uniform panel orientation.

Disadvantages:

Affected by Shading: If one panel in the string is shaded or underperforming, the efficiency of the entire string gets affected.

Limited Flexibility: The design limits the system's flexibility for panel orientation or placement, especially in areas with shading issues.

Microinverters

Microinverters are compact inverters installed on the back of each solar panel in a PV system. Unlike string inverters, microinverters work independently for each panel.

A Micro inverter connects to individual panels reducing potential shading. This micro pictured connects to two panels.

Advantages:

Shading Tolerance: Microinverters mitigate the impact of shading on a specific panel, allowing other panels to perform optimally.

Enhanced Monitoring: They provide detailed, panel-level monitoring, allowing for precise system analysis and issue identification.

Flexible System Design: Each panel operates independently, enabling different panel orientations and configurations.

Disadvantages:

Higher Cost: Microinverters are generally more expensive due to their individualised setup.

Complex Maintenance: If a microinverter malfunctions, accessing and replacing it can be intricate and costly. Scaffolding could be needed to access the panels, compared to a string inverter that could be located in the loft space.

Hybrid Inverters

Hybrid inverters are designed to manage both solar panels and energy storage systems, like batteries. They convert DC electricity generated by the panels into AC for household use and manage the storage of excess energy in batteries.

A hybrid inverter can work with both a solar PV installation and a battery storage system at once.

Advantages:

Battery Compatibility: Ideal for homes considering or already utilising battery storage solutions and Solar P.V.

Energy Management: They optimise energy usage by storing excess electricity for later use, minimising reliance on the grid.

Potential for Off-Grid Capability: In some cases, they can facilitate off-grid functionality for homes.

Disadvantages:

Higher Cost: Hybrid inverters tend to be more expensive due to their additional functionality. Although the added cost is negligible to that of a standard string inverter when you consider the system payback of a 10-20 year period. With costs continuing to come down, they will soon be comparative to that of standard string inverters.

Power Optimisers

Whilst not an inverter it is worth mentioning power optimisers. They operate similarly to microinverters, but they optimise the DC output of each panel before sending it to a central inverter. They're installed at the panel level and offer some of the benefits of both string inverters and microinverters.

Advantages:

Efficiency Enhancement: Optimisers maximise each panel's output, especially in shaded conditions.

Enhanced Monitoring: Like microinverters, they provide panel-level monitoring, aiding in performance analysis and issue identification.

Partial Decentralisation: While they still rely on a central inverter, they provide some decentralisation for panel performance. These devices constantly monitor and regulate voltage, current, and temperature for each panel, ensuring they operate at peak efficiency.

Disadvantages:

Cost: Power optimisers add to the overall system cost, making them a moderate investment and for customers looking for a strong ROI, may not provide what they would like.

Complex Maintenance: More individual pieces in a system inevitably leads to an increased likelihood of issues with the system. Accessing the optimisers post installation can also be challenging, requiring scaffolding to access them in most cases.

Understanding the nuances of each inverter type is crucial in choosing the most suitable one for a solar PV system. Factors like budget, shading, system size, and maintenance preferences should all be considered before making a decision. Consulting with a qualified solar installer can help homeowners make an informed choice that aligns with their specific needs and circumstances.