The 5 key factors to consider when picking a solar inverter

When making any decision, the first step is always to work out what factors are important. In this video, I will be outlining the 5 key factors that you need to be considering when picking your solar inverter.

How do your solar panels and their layout affect inverter selection?

Around 15 years ago, all an inverter did was convert DC power to AC power; now there are a ton of variations and features to consider when deciding on which inverter you want or need. However, the most important factor when determining which inverter you need still relates to system design. Here, we will give a basic overview covering just the most important aspects since we have a dedicated video and post on the intricacies of designing a solar PV system.

The first step is to look at the total size or output of the solar panel array or arrays you are going to install, as this will determine our inverter rating (The simplest way to calculate this is by multiplying the rating of the solar panels by the number of solar panels). Next, we need to look at how the panels in those arrays are arranged. We need to look at how many different orientations and angles we have and whether any of these arrays have sections that suffer from partial shading or intermittent shading. This is so that we can work out how many MPPTs we need so as not to lose out on solar production. If we have a lot of angles and orientations (typically anything more than 3) we might want to consider a micro-inverter or optimiser system to ensure we maximise our output.

 

Key Concept: MPPTs

A Solar MPPT (Maximum Power Point Tracker) optimises the electricity from the solar panels connected to it by constantly finding the point where they produce maximum power. It adjusts voltage and current as sunlight, temperature, or shading changes, ensuring the system always runs efficiently.

 

We also have to look at which solar panels we are installing, as all solar panels have different voltage and current characteristics, even if they have the same power output (panel rating).  This comes into play, as inverters have minimum and maximum voltage and current allowances for each MPPT and the inverter as a whole.  An inverter’s start-up voltage might mean we can have 3 panels of one output in a string, but it might mean we need a minimum of 4 panels of another output. Finally, we need to consider whether we want battery storage to help improve our solar self-consumption. If we do want battery storage, a hybrid inverter will likely be the best option for us. You can find out why in our post and video where we go through the benefits and drawbacks of the 5 types of inverter.

 

How much should you spend on an inverter?

Your budget and goals with your solar PV system will be a significant factor in which type or brand of inverter you want. If solar is a long-term investment for you, then the lifetime system savings and cost are important factors; however, if you plan on selling your home in the next 5-7 years, it might be the payback period that matters more to you. Like with any technology, there are always optional extras that improve user experience, but not the system functionality and inverters are no different.

One of those optional extras is the inverter monitoring system. There is a wide variety of monitoring systems that inverter manufacturers offer, with some providing live output data on a panel-by-panel basis, while others give you snapshots of the inverter’s total output. Although being able to see panel-level data can help you notice and address faults quicker, this optional extra is more of a preference than a necessity. Most of the inverters that provide panel-level monitoring do so as a byproduct of panel-level optimisation.  It is only really with third-party power optimisation, provided by manufacturers like Tigo, where you can choose to upgrade to include monitoring.

When determining how much you should spend on an inverter, it is important to remember that not all inverters are made the same, meaning that they don’t all have the same length of warranty. Again, this is why knowing whether you see solar as a long-term or shorter-term investment will help you decide if you want the initial cost and quality that an inverter with a 20+ year warranty provides. Typically, your mid-range inverters have a warranty between 7 and 12 years, so you can still get good protection at a reasonable cost.

 

How to work around DNO restrictions

As discussed in previous inverter videos, your Distribution Network Operator (DNO) can limit your permitted export. This is only a factor if you want to install more than the 3.68kW limit of a G98 application. If you are below this limit, then you can install your system and have your installer notify the DNO after. However, if you want more output than this but your DNO has restricted what you can export, then you need an inverter with G100 compliance, as this allows you to keep the inverter rating high while limiting the export back to the grid. This is great as you don’t lose out on the power your system can output to cover your home loads, and when the DNO upgrades the network in your area, you are best positioned to reapply for a higher export limit.

In Summary…

These 5 factors of system design, budget, system monitoring, warranty and DNO restrictions are key to helping you decide which inverter you want and need for your solar PV system. I hope that this video and post have helped provide you with a framework for comparing inverters so that you can confidently make the best decision on which inverter you want.