What Is a Solar Inverter and How Does It Work?

Solar Inverters: What Is a Solar Inverter and How Does It Work?

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• What is a solar inverter and how does it work?
• What does a solar inverter do?
• The different types of solar inverters
• Which type of solar inverter is right for your project?

What is a solar inverter and how does it work?

A solar inverter is the component in your solar panel system that changes the direct current (DC) electricity captured by your solar panels into alternating current (AC). AC is the standard flow of electricity needed to power your home appliances and connect to the National Grid, at a nominal 230 volts here in the UK. Put simply, without an inverter in your system you'd be unable to power your home safely from your own solar energy.

A solar panel system is only as efficient as its weakest part, so a high-quality inverter is an essential piece of the set-up. It's the component that maximises the energy your panels generate. Inverters are often overlooked at the design stage, but not at CRG Direct.

What does a solar inverter do in a solar panel system?

Solar inverters are the brains of any solar PV system and play a crucial role in how solar energy is converted and used. Their essential jobs are:

• Converting direct current to alternating current, turning the electricity your panels generate into usable AC power.
• Maximising power output.
• Communicating with the National Grid.
• Giving feedback on power production.
• Providing built-in safety mechanisms so your solar PV system operates safely within your home's electrical system.

The different types of solar inverters

The three main types of solar inverter are string inverters, microinverters, and hybrid inverters. Alongside these primary options there are a few others worth knowing, including AC-coupled inverters and power inverters/optimisers. Below we cover the key characteristics, and the pros and cons, of each. By the end, choosing the right inverter for your property or project should be simpler than ever.

String inverters

A 'string' is a chain of solar panels arranged into groups or rows and connected in series. For a standard string inverter to work efficiently, all the panels in a string should share the same pitch, brand, orientation, and power rating. In many systems one inverter manages multiple solar panels across more than one string, and many string inverters have two or even three MPPTs (Maximum Power Point Trackers). That means you can run a different string of panels on each MPPT, which is ideal for an east/west set-up where the two strings generate at different times of day.

A single-phase model is typical for homes, while three-phase inverters are more common on larger commercial installations. In a typical residential solar installation, the unit is often wall-mounted close to the consumer unit to help keep cabling practical and compliant. String inverters usually carry a 10- or 12-year warranty and remain the standard option for many UK homes, although inverters fail over time so choosing the right solar inverter still matters.

Pros of string inverters

• Cost-effective, with a lower overall system cost that appeals to a typical residential installation compared with microinverters or optimisers.
• Trusted, proven technology, widely adopted in both residential and commercial systems.
• Just a single unit to monitor, update, and service, so maintenance is simplified and installation is straightforward.

Cons of string inverters

• Limited design flexibility. Strings must be balanced in orientation, tilt, and panel type for best efficiency, making them less suitable for complex roofs.
• If one panel is shaded, dirty, or underperforming, its output drags down the whole string rather than just that panel.
• They provide only system-level data unless optimisers are added, which can make fault-finding harder.
• They need a minimum number of panels to generate power, so they're less suited to very small installations.

Microinverters

A relatively new technology, microinverters are small devices fitted directly to the back of each solar panel. Where string and hybrid inverters use one inverter across the entire array, a microinverter gives every individual solar panel its own unit converting DC to AC. Because each panel works independently, issues affecting one panel don't drag down the rest of the array.

Microinverters are ideal for roofs with shading or more complex designs, for example one or more panels facing multiple orientations, or a mix of different brands, wattages, and inclinations. They cost more than classic string inverters, but they can improve a panel's output, increase overall generation, and help systems stay closer to peak power, while a better monitoring platform also makes fault-finding faster.

Popular microinverter manufacturers include Enphase, APsystems, and Sigenergy.

Pros of microinverters

• Easy to expand. Additional panels aren't constrained by the power rating of a single inverter.
• Panel-level optimisation means shading, dirt, or low light on one panel is less likely to affect the rest of the array.
• Enhanced, per-panel performance data makes identifying faults faster and easier.
• Converting DC to AC at panel level removes the need for high-voltage DC cabling inside the property, improving safety.
• Often come with longer warranties of 20-25 years, closer to the lifespan of the panels themselves.

Cons of microinverters

• Higher upfront cost, as every panel needs its own inverter.
• If a single unit needs inspecting, scaffolding may be required at the customer's expense, making one replacement potentially more costly than swapping a string inverter.
• More components mean more potential points of failure, though microinverters are generally very dependable.

AC-coupled inverters

An AC controller, or AC-coupled inverter, is a type of inverter that manages the flow of AC electricity within a system.

For homeowners looking to install battery storage without solar panels to take advantage of time-of-use tariffs, or those wanting to retrofit battery storage to an existing solar system, an AC-coupled inverter is an ideal solution. If a home already has a string inverter, adding batteries usually requires a separate inverter in an AC-coupled set-up. We cover the retrofit route in more detail in our solar and battery installation guide.

Installed alongside a string inverter, an AC-coupled inverter lets you access the benefits of battery storage, storing surplus energy and increasing your use of renewable electricity. In this configuration the AC-coupled unit also acts as a battery inverter, storing surplus solar energy for later.

In recent years the sector has seen integrated solutions such as the GivEnergy All-in-One and Tesla Powerwall 2, which combine an AC controller and battery storage in a single unit. It's a simpler, more compact installation that's proved popular in the UK.

Pros of an AC-coupled inverter

• A cost-effective way to add battery storage to an existing PV system without replacing the current inverter.
• Solar PV and battery storage operate independently, so if one fails, the other keeps working.
• Can be paired with almost any existing solar system, regardless of the inverter brand.

Cons of an AC-coupled inverter

• Less efficient than a DC-coupled system, as the energy goes through multiple conversions (DC → AC → DC → AC), which slightly reduces overall efficiency.

Hybrid solar inverters and battery storage

A hybrid inverter combines the functions of a traditional solar inverter and a battery storage inverter in one unit. If you're installing a new solar PV system with a solar battery, a hybrid inverter is well worth considering.

Because solar panels generate DC and household appliances need AC, a hybrid inverter's power electronics manage the conversion between solar generation, battery charging, and household use. Any surplus DC power can be stored directly in a solar battery or exported to the Grid via a Smart Export Guarantee (SEG) tariff. When your home needs that stored energy, the hybrid inverter converts it back to AC so it can be used safely by your appliances and the National Grid.

This hybrid approach gives you greater flexibility and control, letting you store excess solar energy for use in the evenings or when demand outstrips generation. This configuration is known as a DC-coupled system.

Most manufacturers that offer battery storage also make hybrid inverters. Brands include GivEnergy, Solis, Growatt, and Fox ESS, with Solis often chosen as a cost-effective option for straightforward installations. Newer products such as the EcoFlow PowerOcean feature a stackable hybrid inverter and battery system for modularity, while the Tesla Powerwall 3 has a hybrid inverter built directly into the unit for easier installation.

Pros of a hybrid inverter

• Integrated with your solar battery and panels, it centralises monitoring for smarter energy management, letting you optimise self-consumption and export control from one platform.
• Direct DC coupling between panels and batteries minimises conversion losses, keeping the system highly efficient.
• A compact all-in-one solution that combines solar and battery management, saving space compared with separate systems.

Cons of a hybrid inverter

• If you already have solar panels and just want to add a battery, it's usually more cost-effective to install an AC-coupled battery system than to replace your existing inverter.
• Hybrid inverters are around 50% more expensive than string inverters. They also only integrate with DC-coupled batteries, and because they're designed around specific storage configurations, that can limit your battery choice.
• The hybrid inverter is a single point of failure, so if it fails, both solar generation and battery functions are affected.
• Sizes are still evolving, but many residential models currently top out around 6 kW, which can limit how many panels you install before needing a second unit. String and microinverter systems generally offer more flexibility here.

Power inverters (DC power optimisers and MPPT)

Power inverters, also known as power optimisers, offer many of the same benefits as microinverters and are likewise fitted behind each individual panel. Like microinverters, they provide panel-level optimisation and monitoring, perfect for shading and complex designs. But instead of converting DC to AC at roof level, a power optimiser conditions the DC output from each panel and passes it to a traditional string or hybrid inverter (usually located near your battery storage) for conversion.

Power optimisers are generally a more cost-effective alternative to microinverters. SolarEdge is the market leader, with its inverters working exclusively alongside SolarEdge power optimisers to deliver module-level Maximum Power Point Tracking (MPPT). This type of installation gives you increased generation, advanced fault detection, and enhanced safety features such as arc-fault detection.

Brands such as Tigo make power optimisers that work with virtually any inverter, while the likes of Sungrow, Huawei, and SolarEdge pair their optimisers with dedicated inverters designed for maximum performance.

Pros of a power inverter

• A cheaper alternative to microinverters, offering many of the same benefits at a lower price point.
• Maximise energy production by reducing the impact of shading and mismatched modules, allowing greater design flexibility.
• A SolarEdge string inverter offers up to 99% conversion efficiency, so very little of your generation is lost.
• Some brands, such as Tigo, are compatible with a wide range of inverters, so you can enjoy the benefits of optimisers alongside your preferred inverter.
• Detailed per-panel performance data makes fault detection easier and gives greater overall visibility.

Cons of a power inverter

• Optimisers still rely on a string, central, or hybrid inverter to convert DC to AC, so unlike microinverters they aren't fully independent. If that main unit fails, the whole system stops producing power.

Which type of solar inverter is right for your project?

Several factors shape the right inverter for your project. The best choice depends on the inverter type, your property's supply, and whether the project is single- or three-phase. It may also come down to your budget, roof configuration, safety requirements, whether you plan to add battery storage, and whether you need off-grid capability. Most domestic inverters are designed for homes, while three-phase or larger-format systems suit bigger properties and commercial electrical systems. Here's a summary of the main options:

• String inverters: cost-effective and reliable, often the standard choice for unshaded roofs where all panels face the same direction and battery storage isn't planned from the outset.
• Microinverters: ideal for complex roofs with shading, multiple orientations, or mixed panel types, offering per-panel optimisation and monitoring.
• Hybrid inverters: best for new solar PV systems that include battery storage, enabling efficient DC-coupled energy management and backup power during a power cut.
• AC-coupled inverters: perfect for retrofitting batteries to existing solar systems without replacing the current inverter, or for a standalone battery solution.
• Power optimisers: combine some benefits of microinverters with a string set-up, improving performance on partially shaded or mixed-panel arrays at a more affordable price point.

At CRG Direct we offer free consultations to design a bespoke solar panel system tailored to your needs. As MCS-certified installers designing and fitting solar, battery, and hybrid systems across the South and South East of England, you can trust your project is in safe hands. Call us today on 0330 133 2497 or book your free survey to speak with a solar expert about inverter compatibility, likely maintenance costs, and what your system can show through monitoring.