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Solar panels use photovoltaic (PV) cells to convert daylight into electricity. However, this electricity is in the form of a direct current (DC), while most household electrical devices operate from an alternating current (AC), so solar energy needs to be converted from DC to AC in order to power your home.
This is where a solar panel inverter comes in. It is an essential device for any solar panel system – and there are a few different types available on the market. Here, our experts explore the purpose of solar inverters in more detail, and how to choose the right one for your system’s installation.
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Let’s dive deeper into three core types of solar inverters: microinverters, string inverters and hybrid inverters.
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.
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 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.
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.
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.
Solar inverters have moved on a bit in recent years and it is worth looking at inverters that can also control a battery. These are known as hybrid inverters. Not all hybrid inverters are the same, though, so do your research for different battery systems and then get a compatible inverter. Some inverters also have functionality that can be controlled by some smart home systems, which will allow the smart home system to manage the generation and battery discharge to optimise the use in the home.
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.
Modern solar inverters may offer different connectivity options for connecting them to monitoring and diagnostic equipment, including:
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:
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:
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:
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.
A solar panel inverter is responsible for converting the direct current (DC) power generated by your solar panels into alternating current (AC) power, which is the standard used by most electrical home appliances.
While installing a solar inverter yourself is technically possible, it’s generally only viable if you’re a certified electrician or have substantial experience.
Working with electrical systems can be hazardous, especially for those unfamiliar with the correct procedures. It’s also worth noting that many manufacturers will only honour warranties if certified professionals install their products.
The best solar inverter for residential use can vary depending on your specific needs, solar array size, and budget. Some top-rated brands to consider are SMA, SolarEdge, and Enphase. SMA is renowned for its string inverters, while SolarEdge and Enphase are known for their power optimisers and microinverters.
The lifespan of a solar inverter can vary greatly but, on average, you can expect a good-quality inverter to last between 10 to 15 years.
Contact manufacturers or distributors directly or work with a solar installation company to obtain quotes for solar inverters. Many companies provide free quotes either online or over the phone. Be sure to get quotes from several sources to get a fair comparison.
Various factors, including demand and production levels, can influence the best time to buy an inverter for solar panels. depends on various factors, including demand and production levels.
Focus on getting the best quality and value rather than waiting for a specific time of year, and keep an eye out for any sales or discounts that manufacturers or retailers offer throughout the year.
