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Solar Inverter Efficiency and It’s Real-World Applications

Feature image for "solar inverter efficiency" blog. Image shows a 2-story Victorian home with rooftop solar panels surrounded by matrix-style numbers and percentages.

Sometimes we want everything to be as simple as looking at an efficiency rating on a product and then getting exactly what we expect. I have to tell you, though, that number alone doesn’t encapsulate the whole story.

Solar inverter efficiency ratings are not an outright lie; however, product managers would of course want to present their baby in the best possible way. But that’s where we come in!

In this article, we’ll outline all you need to know about efficiency ratings and if they are even trustworthy, the efficiency curve, and all else you need to know in order to make the best purchase decision. Here’s all the major topics we’ll go through; feel free to skim.

2 efficiency ratings you need to know about

Like I’ve alluded to before, it’s not all so simple. In an effort to keep things as easy as possible, though, you only need to know about two types of efficiency ratings: peak efficiency and weighted efficiency.

1. Peak efficiency

Peak inverter efficiency is simply the highest number an inverter is capable of promising. Do note, though, that when products are tested, they’re placed in the best possible conditions; therefore, it is expected of the product to get the highest score it is capable of.

Peak efficiency is also a number that’s typically plastered in front of appliances (fridge, AC, etc.) because it’s meant to impress buyers. However, as you may already understand, this doesn’t tell the whole story. As a matter of fact, most solar inverters operate at peak efficiency for a very small proportion of the day, if at all.

This brings us to a reliable type of inverter efficiency rating.

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2. Weighted efficiency

Unlike peak efficiency, weighted efficiency is a more real-world depiction of your inverter’s capabilities. “How so? ”, you ask. Good question.

This type of efficiency takes into account the different factors affecting your inverter’s performance, including the temperature and solar irradiance levels that fluctuate throughout the day.

That being said, there are resources you can look at:

  • California Energy Commission (CEC), and
  • European efficiency

Both agencies have lists that show the weighted solar inverter efficiency of various products. Although if you can’t find the inverter efficiency of the product you’re eyeing, you also have the option to ask anyone in our network of pre-vetted solar installers. Oh, and don’t worry. Our quotes are FREE.

You know what might be even better than weighted solar inverter efficiency, though? Curves.

The inverter’s efficiency curves

Efficiency curve of the Huawei SUN2000 inverter
Efficiency curve of the Huawei SUN2000 inverter

While weighted efficiency shows you a single number to represent the real-world power output of solar inverters, an inverter’s efficiency curve shows that to you in the form of a graph. You get a fuller picture this way.

The graph represents the changes that your inverter’s efficiency goes through relative to its rated capacity.

This is an important consideration because it could also help you decide the appropriate size inverter for your home. Solar inverters that are too large relative to their solar panels won’t be efficient, but a solar inverter that’s too small might also lead to excessive solar clipping.

I’ll reserve the more in-depth discussion for another article, but the gist is that you’ll want to be on the “good” side of the curve, where your inverter operates at over 80% of its maximum efficiency while also outputting close to its rated capacity.

How to find out your system’s efficiency for yourself

Manufacturer’s specification sheet

Do this first so you can set your expectations appropriately. Usually, you can find this at:

  • The user manual that came with your system
  • The website of your inverter manufacturer
  • Data sheets (which typically come with the manual)
  • Product labels
  • Sales literature (brochures and whatnot, usually handed out during purchase)

Built-in monitoring system

Many modern inverters come with a built-in monitoring system that can track and report the performance of your hardware.

If you need help, we discuss how to read the information on your inverter’s display here.

Solar inverter output levels vs. solar panel output levels

Get data on both. Solar panel input is in DC, while inverter output is in AC. You can check both via the system’s monitoring panel. You’ll know if your system is operating optimally if your inverter’s output closely matches the DC input power of your solar panels.

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Look at performance on a macro scale.

Track data for, say, about six months or more. If, over a long period of time, you do not notice a significant decline in performance, then your solar system must be performing optimally.

Consider hotter days.

It is important to remember that the efficiency of your solar system will naturally drop as the ambient temperature increases. Don’t mistake this for a deficiency, and consider this in your calculations.

Related: When are solar panels at their most efficient?

If all that sounds like too much of a hassle, don’t worry. You can always ask professionals to do this for you. And, remember, our network of pre-vetted solar installers can give you quotes and answer your questions FREE.

Conclusion

Recap time! Firstly, we’ve learned that spec sheets and touted numbers are only part of the story. Next, it’s better to have a solar inverter consistently perform at a high efficiency rating than go for one that has a higher maximum energy efficiency rating but cannot sustain itself over a period of time.

That’s where weighted efficiencies and efficiency curves come into play. For most people, the weighted numbers are more than enough. If you’re the type to always cross your t’s and dot your i’s, though, then you’ve got the curves of your particular inverter to look at as well.

And, last but not least, you can always ask for help from the pros. Our network of pre-vetted solar installers is ready to help right away. Just let us know, and we’ll send 3 FREE quotes from them your way.