What types of solar inverters are available in the UK? How do they work? And most importantly which should you choose for your system?
Are you wondering exactly what solar inverters do? And which type is best for your solar installation?
To tackle the first question first, solar inverters do not turn the sun inside out. Instead, the inverter's function is to convert the electricity your solar panels generate (DC) into the type of electrical current your household appliances and the National Grid use - alternating current (AC).
There are four main types of inverters you can use with solar: string inverters, microinverters, hybrid inverters and power inverters. Magic inverters, which require no costs, installation, or maintenance, have not been invented yet.
While they all carry out the same primary role - converting DC to AC, in many ways, they are not the same and in this guide, we'll explore each of them, their use cases, along with their pros and cons.
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Solar Panel Inverters Key Points:
There are four main types of solar inverters: string, microinverter, hybrid and power.
If you have solar battery storage with your solar array, consider a hybrid inverter.
String inverters are the cheapest, but have significant limitations.
Microinverters are viewed as the gold standard but their upfront costs are greater than other types.
What is a Solar Inverter?
The main role of an inverter is to convert direct current (DC) to alternating current (AC).
The reason for this is that AC is what household appliances and circuits use, so without an inverter the electricity our panels generate would be practically useless.
However, in addition, solar inverters also execute the following roles:
Convert direct current to alternating current.
Maximise power output.
Communicate with the National Grid.
Providing feedback information about power production.
Ensuring that your solar PV system is operating safely.
This gives you another consideration in buying solar panels that might keep you up at night.
Different Types of Solar Inverters
There are four main types of inverters you can use with solar: string inverters, microinverters, hybrid inverters and power inverters.
While they all have a similar role to play, there are significant differences between them:
String Inverters (Central Inverters)
As their name implies, a string inverter (also sometimes called a central inverter) is designed to manage and convert the power from groups or all of the solar panels - these are fed to the inverter via a series of strings.
For example, you may have 16 solar panels fed to the inverter using two strings, i.e. a series of 8 solar panels on each circuit being fed into the inverter unit.
A string inverter converts the output of all panels within the system at once (from DC to AC).
However, a string system needs all the panels in the series to be exposed to the same environment e.g. the same pitch and orientation - if not, the panel's power output can be seriously impacted.
For example, in an east-south set-up, this can be useful since the power output of each will be slightly different, therefore, you could separate both east and west onto separate strings.
Pros:
Cheaper than other options.
Cons:
Performance issues in low light and shading.
Decreased power output compared to microinverters.
Installation design limitations.
Requires a minimum number of solar panels to begin power generation.
Not as safe as an AC-optimised microinverter.
Micro Inverters
Unlike a traditional string inverter that converts the output of all panels within the system (from DC to AC), a microinverter is attached to each solar panel within the system, allowing for the independent conversion of each panel’s output locally.
Micro inverters have a whole host of benefits and significant advantages over string inverters, so are now viewed as the gold standard by many.
This includes increased energy production due to individual panel optimisation, improved system reliability through redundancy, and simplified installation and maintenance.
Additionally, microinverters allow for real-time monitoring of individual panel performance, which can help with system maintenance, troubleshooting and behaviour changes.
Pros:
Better performance - overall power output is not impacted by shading.
Cheaper in the long run - 25-year warranty vs standard string inverter warranty of 12 years.
Optimised for low light - perfect for a cloudy place like the UK.
Safer AC current optimised design.
Cons:
More expensive upfront.
Hybrid Inverters
A hybrid solar inverter combines the functions of a traditional solar inverter and a battery storage inverter into one unit.
As a result, a hybrid inverter is able to store incoming energy in direct current (DC), as well as convert the DC into AC, while also sending any surplus DC power to be stored in a solar battery or to be sold to the grid.
When this stored energy is in demand, the inverter can then convert the electricity to AC to be used in your household (AC is what our appliances and the National Grid use).
This hybrid approach means that there is increased flexibility and control over energy usage, as well as the ability to store excess solar energy for use in the evenings.
A hybrid inverter is a perfect solution if you are planning on installing solar panels with a storage battery.
Pros:
Ideal for solar set-ups with battery storage.
Cons:
Around twice as expensive as standard string inverters.
If you have an existing system it is cheaper to install an AC-coupled inverter instead.
They often only work together with DC-coupled batteries.
Related solar guides:
Power Inverters (DC Power Optimisers)
A power inverter, also referred to as a power optimiser works in a similar fashion to a microinverter unit in that each solar panel has its own.
This means that power can be controlled on an individual panel level and allows their performance to be monitored.
The main difference between a power inverter and a micro inverter is that the DC current generated by the solar panel is not converted locally. Instead, the DC current is transferred through to a traditional string inverter.
Power inverters are generally viewed as a cheaper alternative to microinverters.
Pros:
Cheaper alternative to microinverters.
Limits the impact of shading on overall power output.
Cons:
Warranty generally not as generous as microinverters.
How to Choose the Right Solar Inverter
It really depends on two main things: your budget and project goals.
However, choosing the best type of solar inverter for your home also involves considering factors such as the size of your system, efficiency, type of panels, grid-tied or off-grid, brand and warranty, and budget.
What Size Solar Inverter Do You Need?
Choosing the correct size solar inverter is essential to ensuring it can execute its primary role, but it's also important for the longevity of your battery storage (if you have any, that is).
Typically, it's advised that you slightly undersize your inverters so that they are slightly below your solar array's maximum power output.
The reason for this is that solar panels rarely hit the maximum power output, so you are unlikely to need an inverter that is any larger. This also helps to prolong the life of your battery storage.
For instance, if you have a solar panel system with a maximum output of 3.5 kW, then you would typically install a 3kW inverter and not a 3.5kW inverter.
How Long Do Solar Inverters Last?
The lifetime of the inverter depends on the type and quality of the unit.
Traditional string inverters typically last around 10 years and come with a warranty period between 10 and 12 years.
Microinverters are more expensive to buy, but they typically last for around 25 years and come with a 25-year warranty too.
For example, the Enphase microinverter reports a 1 in 2000 failure rate and they’re backed by a full replacement 25-year warranty.
In a 25-year life of a system, you’d need to budget at least two replacement string inverters (these carry a warranty of between 5-10 years) and would cost in the region of £1000-£2000 each time, plus any loss of generation as the whole system will be down.
Microinverters are also likely to maximise your system's power output, so are likely to be well worth the extra cost.
Maximising your system's power output ultimately means more money for you to use and save, it also means you can sell more energy via the Smart Export Guarantee (SEG).
Important note: not only is the sizing of your microinverter important for practical reasons, but many inverter manufacturers will void the warranty if it's not used with the recommended solar array size.
Still learning about solar panels? Explore our helpful guides on various topics, including solar panel grants, payback periods, the mechanics of solar energy, determining the number of panels you need, and solar car charging solutions.
Next Steps For Your Solar Journey:
When planning to install solar panels for your home, there are several important factors to consider. Make sure to refer to the following guides to help you make informed decisions:
To dive deeper into these topics, head over to our advice section, check out our YouTube channel for informative videos, or read a customer case study to see how others have benefited from their solar installation.
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