Solar Inverter Efficiency: What you need to know before buying.

Everything goes through the inverter so its efficiency is critical.Solar inverter efficiency is a critical specification that directly affects the efficiency of your entire solar system. It is almost always a much more important consideration than solar panel efficiency.

All the power generated by your solar panels has to go through your inverter before you can either use the power in your home or export it to the grid (and get paid) so every percent of extra efficiency that you can squeeze out of your inverter will directly improve the performance and payback of your solar system.

So do you just need to pick the inverter with the highest “efficiency” number on the specification sheet? Well I’m afraid it isn’t quite that simple. (You guessed I was gonna say that didn’t you?!)

Can You Trust The Efficiency Quoted On the Specification?

Most grid connect inverters for sale in Australia will have a “peak efficiency” specified by their manufacturers of between 94% and 98%. If you are ever offered an inverter with an efficiency of less than 94%, don’t even go near it!

However, as you might expect, the solar inverter manufacturers all want to paint their inverters in the absolute best light, so when they measure this efficiency they make sure that all the conditions are absolutely perfect in the lab for maxing out the inverters efficiency. The result is that you are very unlikely to ever get the efficiency quoted on the specification in real life. Bummer.

The simplest way to work out the ‘real world’ efficiency of any particular inverter is to take advantage of some hard working government labs in both California and Europe who have taken it upon themselves to crunch a whole load of numbers for each and every inverter in their respective markets, and calculate an efficiency that is a lot more realistic than the manufacturers’ numbers.

You can find the Californian Energy Commission’s CEC Efficiency here for all the inverters approved for use in Arnie Schwarzenegger’s state. (This is the first place to look because those nice Californians also give you a “real world” power output rating for each inverter, so for example, you can see if your 2kW inverter really can handle 2kW, or whether it is more like 1800W…)

And if you don’t find your inverter model there, then you can look up an inverter’s European Efficiency in this database.

If you’re comparing different inverters then make sure you only use one type of efficiency (CEC or European) for every inverter in the comparison, to ensure you are comparing apples with apples.

So now you know how to find an inverter’s “real world” efficiency, you probably know more than some solar salesmen out there knocking on doors! Sad but true…

If you want to get even deeper into the joys of solar inverter efficiency specifications, you’ll be ecstatic to hear that I haven’t even started on the joys of the inverter efficiency curve. This lesser known inverter specification can make or break your solar system performance, and it is so important I’ve devoted an entire blog post to the subject.

About Finn Peacock

I'm a Chartered Electrical Engineer, Solar and Energy Efficiency nut, dad, and founder of SolarQuotes.com.au. My last "real job" was working for the CSIRO in their renewable energy division.

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