Best solar inverter guide 2024

Solar panels use photovoltaic (PV) cells to convert sunlight into electricity. This generates a direct current (DC) that needs to be converted into an alternating current (AC) accepted by most household electrical devices. 

Converting DC into AC requires the services of an inverter, an essential device for any solar setup. Inverters are relatively simple in technological terms, but there are a few different types available.

This guide explores the purpose of solar inverters and how to pick the right one for your installation.

Let’s dive deeper into three core types of solar inverters: microinverters, string inverters and hybrid inverters.

Microinverters

Microinverters are small inverters located on each solar panel. They convert DC to AC at the panel level, which means each panel can operate independently. 

This setup ensures the other panels remain unaffected if one panel is underperforming, perhaps due to shading or dirt. This is particularly beneficial for roofs with complex shapes or orientations, where shading may be an issue.

On the other hand, microinverters are more complex to install and are generally more expensive upfront because you need one for each solar panel. 

String inverters

Unlike microinverters, a string inverter is a single unit that serves all the solar panels in your array. The solar panels are connected in a series, creating a “string”, and the generated DC is sent to the central string inverter to be converted into AC.

String inverters are more cost-effective than microinverters, as you only need one per array. They’re also easier to maintain and replace when necessary. However, if one panel performs poorly, it can affect the output of the whole string.

Hybrid Inverter

Hybrid inverters work the same as any inverter – converting DC to AC – but also handle power exchange with solar battery storage systems and the mains grid (hence the term ‘hybrid’), depending on the model.

Without a hybrid inverter, you’ll need a battery inverter to exchange power with a battery.

Choosing a hybrid inverter means that if your solar panels generate more power than you use, the excess energy can be stored in a battery for use later or exported to the utility grid. This could enable you to take advantage of the Smart Export Guarantee (SEG), where some energy companies will pay you for the excess energy you generate and feed into the grid. 

Although a hybrid inverter may have a higher upfront cost and require a compatible battery system, they’re a versatile choice for many domestic setups.

When it comes to selecting the right solar inverter for your setup, there are a few things you need to consider.

Understanding the efficiency of inverters

One of the first features to consider is the inverter’s efficiency, typically expressed as ‘European’ or ‘weighted’ efficiency. This rating measures an inverter’s performance under realistic, varying conditions, not just perfect lab scenarios. 

Inverters usually operate with an efficiency of 95 to 98 per cent, but even minor differences in this figure can significantly affect the system’s long-term output. 

Matching power ratings

When planning your solar array, you’ll need to consider the power rating of your inverter. This rating stipulates the maximum load an inverter can handle, effectively defining how much power your system can yield. 

For instance, suppose your solar panels have a peak output of 6kW during optimal sunlight hours. In that case, you’ll most likely want an inverter with at least a 6kW power rating to fully harness this potential.

While selecting an inverter with a significantly higher power rating may seem logical to prepare for possible future solar array expansions, this isn’t usually the best course of action. Instead, industry best practices typically recommend sizing the inverter to approximately 75-90 per cent of the solar panels’ peak power output.

To illustrate this, let’s say you have a solar panel array with a peak power output of 10kW. Rather than getting an inverter with a 10kW capacity or larger, you might choose an inverter with a power rating of 7.5kW to 9kW. This practice, called ‘inverter clipping,’ considers that solar panels rarely operate at peak capacity due to variables such as shading, cloud cover and the angle of the sun. 

The benefit of the clipping approach is twofold: it can improve the overall efficiency of your solar system and save you money by avoiding the unnecessary cost of an oversized inverter. Remember, an inverter significantly larger than required might not operate efficiently at lower power levels, leading to wasted capacity and increased upfront costs.

However, finding the right balance is crucial, as an inverter with insufficient power will restrict your system. Once you determine the size of your solar array, you can ask a professional about what inverter power rating is ideal and whether you should consider inverter clipping. 

Inverters come with varying input voltage and current requirements, which must align with your solar panels’ specifications.

For example, if your solar panels produce a maximum output voltage of 350V, you need to select an inverter designed to operate within that voltage range.

Suppose your solar panel array has an open-circuit voltage (Voc) of 400V and a maximum power point (Vmpp) of 350V. 

In this case, you should choose an inverter with a maximum input voltage exceeding 400V (to handle the panels’ Voc safely) and an MPP voltage range of 350V.

Many solar inverters can now be controlled digitally via software and smartphone apps. 

A solar inverter with a monitoring system can offer comprehensive, real-time insights into your solar setup’s performance. They act as a 24/7 diagnostic tool for your solar power system, which is excellent for monitoring changes in performance over time.

These monitoring features enable you to gauge how much energy your solar panels are generating and track the conversion efficiency of your inverter. 

Monitoring systems can also detect potential issues within your system, helping you determine when to clean your solar panels. 

Understanding data connectivity options

Modern solar inverters may offer different connectivity options for connecting them to monitoring and diagnostic equipment, including:

• Wifi connectivity: Some inverters can seamlessly connect to your home’s wifi network, allowing you to access real-time and historical performance data through a dedicated smartphone app or a web interface. 
• Wired connections: Alternatively, some solar inverters have a wired connection to a dedicated display device installed within your home. This can be useful if your wifi connection is unstable or you prefer a dedicated physical display for your solar system’s data.
• Cellular data: Some high-end inverters may offer cellular data connectivity via 4G or 5G, eliminating the need for wifi or wired connections. This can be a valuable feature if your solar system is installed remotely.

Now that you’ve picked the perfect solar inverter, where do you put it? 

Overall, most inverters are best placed in a garage, utility room, or other dry but well-ventilated room. Some models are designed for external mounting. The loft is generally considered a poor place to install an inverter, as loft temperatures fluctuate. 

Here are some tips for choosing the best place to install your inverter:

• Read the inverter’s guidelines: First, check the manufacturer’s guidance for how and where to install the inverter and best practices.
• Ask your solar panel installer: The company installing your system may have recommendations for the best location, based on their experience and the initial inspection of your house during the quoting process. 
• Cool, well-ventilated spaces are best: Inverters can generate heat during operation, so they need a well-ventilated area. Also, keep them away from direct sunlight to prevent overheating. Some are noisy, which is something to bear in mind. 
• Consider access: Place your inverter somewhere accessible for easy maintenance and monitoring. 
• Safe from damage: Keep the inverter off the ground and away from potential sources of water damage.

Solar systems should be installed by a qualified installer or electrician. Mistakes can make the overall cost of solar panels installation rack up, and it’s better to install things correctly the first time to avoid re-arranging components. Moreover, solar systems can produce powerful electric shocks with the capacity to seriously injure or kill in some circumstances. 

Here’s what to expect from the installation process:

• Placement and measurement: Solar inverters are typically mounted on the wall to improve ventilation. However, some are designed to be placed outside. Check the manufacturer’s guidelines for recommended placement. 
• Brackets and fitting: The installer will securely mount the provided brackets (or appropriate alternative) onto the wall.
• Mount the inverter: Wall-mounted inverters are carefully hung on the brackets, ensuring they’re level and secure.
• Connect the system: Finally, the inverter will be connected to the solar panels and home’s electrical system per the manufacturer’s instructions. 

Given the inherent electrical nature of solar installations, professional installation is recommended. Solar systems can still administer potentially lethal electric shocks, plus mis-connecting your components could risk catastrophic damage. 

A professional installer or electrician will correctly fit your inverter as per the manufacturer’s guidelines, avoiding any potential issues that might void the warranty. 

Here’s a breakdown of crucial safety guidelines for setting up and operating solar inverters:

• Switch off the power: Before working with a solar array, switch the solar system off to avoid electric shocks.
• Use the right tools: It’s essential to use the right tools and safety gear for the job. Solar systems can still produce enough of an electric shock to kill under specific circumstances. 
• Know your limits: Avoid working with live wires or making connections if you’re not a qualified electrician.
• Follow manufacturer guidelines: Inverters must be installed as per the manufacturer’s guidelines to ensure safety and efficiency.
• Consider the environment: Solar inverters should be installed in a cool, dry place to avoid overheating and damage from moisture.
• Regular maintenance: Once installed, inverters should be professionally maintained and serviced as per the manufacturer’s guidelines. 

Solar systems are still electrical systems and can produce sufficient electric current to severely injure or even kill. Don’t hesitate to seek professional help from qualified installers.

Solar inverters are integral to solar power systems, converting DC power from PV cells to usable AC. 

Whether opting for microinverters, string inverters, or hybrid inverters, each has its own benefits and potential drawbacks. It’s also important to consider the efficiency and power rating when choosing an inverter, and how these factors impact the overall performance of your solar system. 

Remember compatibility and sizing – an inverter must be able to work seamlessly with your solar panels and be just the right size to function efficiently.

If you’re unsure about how to choose an appropriate inverter, seek professional assistance. Correctly matching and installing your inverter is essential to the overall functionality of the solar system.