Should I oversize my solar inverter?

While it seems counterintuitive - surely your solar panels and inverters should match in terms of the energy they can process, right? - the truth is a little more complicated. There are so many different factors to consider when installing solar panels, and this is one that we reckon is often overlooked.

If you want to learn more, please visit our website Senergy.

Read on to discover what oversizing solar inverters actually entails, how it works, and whether it&#;s the right choice for your solar array installation.

What is an inverter?

An inverter is the heart of your solar installation. It&#;s a central component that makes it all work for you! The inverter is the part of your system that transforms the DC energy (Direct Current energy) created by your solar panels, into AC (Alternating Current energy) which powers your home or facility.

Without an inverter, there&#;s no way to utilise the energy that&#;s produced by your solar panels!
There&#;s a large range of solar inverters in the market, and they can be narrowed down to 3 main types of inverters. The type of inverter that works for your situation may not work for others, and vice versa, so it&#;s vital that you opt for an inverter that is suited to your specific needs.

What is a solar array?

Simply put, a solar array (or PV array) is the term used to describe a group of solar panels. When you&#;ve set up a solar system on your property, that&#;s a solar array! &#;&#;How many solar panels you need - and therefore the size of your array - will depend on your household or facility&#;s solar needs. 

In addition to how you use the energy powered by solar panels, there is also consideration for how much sun you get during the day and how that impacts the average efficiency of solar panels. And that&#;s where inverter oversizing comes in!

What is Inverter Oversizing?

As we mentioned further up, oversizing solar inverters refers to when you install a solar array (that&#;s a group of solar panels) with a higher capacity than the rated size of your inverter. Basically, you install more solar panels that your solar inverter capacity is meant to handle.

For example, say you have a 5kW Inverter. This is the most common size in Australia because most energy providers cap the electricity export for homes at 5kW. This means that at any period in time, your solar system can&#;t export more than 5kW of energy to the Grid. Exporting excess energy to the grid is what happens when you don&#;t self-consume the energy yourself.

In theory, it would make sense to match a 5kW Inverter with 5kW worth of panels - and many people do this. For such a setup, 5kW of panels will equal 15 panels at 330Watt each. But when you opt for inverter oversizing, you&#;re setting up more than 5kW worth of panels instead.

On the surface, this does seem a bit odd. Why &#;waste&#; all that extra energy if you can&#;t use it or put it back into the Grid, right?

If you want to learn more, please visit our website OEM commercial inverters manufacturer.

Well, we&#;ll tell you why it&#;s actually a good idea!

Hi Amit, I&#;m thinking there might be an advantage to &#;oversizing&#; an inexpensive inverter that&#;s convection-cooled, rather than spending more on one which is fan-cooled (or has a better thermal design in some other way). I say this because my best-guess is that my five year old Goodwe NS- will derate itself (perhaps by limiting its output current) when it overheats&#; and I think some modest level of overheating happens after a few hours above 40% or 50% of its maximum-rated power input.

I believe it&#;s routine to derate power electronics when they get above 45 degrees C, to avoid premature failure.

The spec sheet on the Goodwe NS- is pretty minimal with respect to its operating conditions, saying only &#;-25~60°C (>45°C derating)&#;.

This inverter is mounted indoor, pretty high up on a wall in a hallway that&#;s pretty well ventilated. It rarely gets above 30 degrees C at my location in Auckland NZ. The inverter runs pretty hot under even this modest loading, for example I&#;m looking at a day last week when its temperature crawled above 48 degrees C at 2pm &#; when the panels were producing about W. Peak that day was 12.50pm &#; panels producing W. My rooftop array is small: 6x Peimar 300/305WP Mono SG. The maximum they have ever produced is about W, i.e. they wouldn&#;t overrun a Goodwe NS- &#; unless it is derated for high-temperature operation. But I&#;m thinking a Goodwe NS- would run even hotter when powered above W than my Goodwe NS- &#; which seems ok (albeit a bit marginal) in my installation.

All to say that I&#;m thinking that a convection-cooled inverter similar to the Goodwe NS line might appropriately be derated &#; perhaps by 30% or even 50% &#; even when it is run indoor in a mild climate near sea level (e.g. Auckland NZ at 300m). The idea is to avoid it ever running hot (i.e. degrading its life-expectancy by being under high load at a temperature much above 40 degrees C), and also to avoid it ever throttling itself (to avoid overheating) which will result in some of the available PV power &#;going to waste&#;.

I don&#;t yet know &#; but plan to do some analysis on 5 years of data from this installation &#; whether either of these &#;bad things&#; is occurring at all frequently on my Goodwe NS- with an array on the roof that never produces more than 2kW.

I don&#;t expect to find any detailed specs on Goodwe NS- thermal performance under load (as that&#;d depend on operating conditions e.g. ambient temperature and altitude)&#; but I have found a failure-rate plot for a power thyristor at https://www.darrahelectric.com/uploads/techLib/Dynex-AN-Effects-of-Temp-on-Thyristor-Performance__.pdf, which I&#;d guess would more-or-less applicable to the failure-prone power electronics inside the Goodwe NS-.

Amit, can you perchance point me at anyone who has analysed the operating performance of the Goodwe NS- at all carefully, or point out some mistake or misunderstanding in what I wrote above?