The Good, Bad, and The Dirty of Solar Inverters (And Bonus – The Best)

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What is a solar inverter? And why does it matter? The solar inverter is the contraption on a solar system that converts Direct Current (DC) power into Alternating Current (AC). That is important because your solar system produces DC power, but your home, business or house of faith runs on AC power. In fact, the entire US power grid runs on AC power.

So if inverters just convert the DC power to AC, is there a difference between them? And if so, why should I care? My answer to that is yes there is a difference, and YES – YOU SHOULD CARE!!! Why? Do you own a cell phone? What if I told you I could sell you a cell phone with all the bells and whistles we’ve come to expect, but it had three battery options; one works well most of the time, but would randomly shut off, another that works all the time, but only has a 2 hour battery life, and the third that works all the time and had a 12 hour battery life. Which one would you want? What if they all cost the same price? I think you would choose the one that worked all the time with the longest battery life.

string inverterOriginal solar inverter technology, called string inverters, could be compared to the cell phone battery that only works sometimes. The reason for this is that string inverters worked much the same as old Christmas tree lights. Remember how on the old lights if you lost one bulb you lost the entire string? Well, that’s how a solar string inverter works. If one panel was shaded, you could loose an entire string. That means if you had 20 panels, in two strings of ten, and you lost one panel, you would loose 10 panels, half your system. That’s no fun, and a huge waste of power potential.

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 The next generation of inverter technology was micro inverters. Micro inverter technology was a huge leap forward, as we could put a small micro inverter on the back of each panel. This meant if you had the same 20 panels, and one got shaded, it would only affect that panel; the other 19 panels would still be producing power. Sweet, right! However, there were two problems with this technology: one, communication. With each panel now independent of each other, there was no voltage or current regulation between panels. Hence, your system was less efficient than it could be. Two: capacity. When micro inverters first became common, the average solar panel was producing between 170 watts to the low 200’s. With micro inverters converting at 215 watts per panel, this worked. However, as panel wattage increased to 250 watts, and micro inverters only converting 215 watts, clipping occurred. That means you would LOOSE 35 watts per panels. And that’s a lot of power to loose!

In recent years this has become a sore subject in the solar industry. A lot of shady systems have been sold with customers none the wiser. The “Ugly” of this article concerns this despicable practice. Earlier this year, I received a phone call from a potential customer who wanted to compare solar options. He told me that he would not tell me anything about the other quote, but I asked him to at least tell me the wattage of the panel so I could give him a comparable proposal. He said it was a 265-watt American panel. At the time there was only one common 265 watt American panel, Solar World, and it was a terrific product. So I told him that he must have a Solar World proposal, which it was a great panel, and I would match it. I also told him, that my only concern would be if he was quoted a 215 watt micro inverter, as he would be loosing 50 watts of power per panel.

When we met, one of the first things he said to me was that I was right about the panel brand being Solar World, and that I was also right about the micro inverter. That’s how he knew that I, and Rayah Solar, were true solar experts. He also was thankful that I warned him about the common practice in the solar industry of selling undersized cheap micro inverters. As you may suspect, he ended up buying a solar system from Rayah Solar, and today he has a beautiful 28-panel solar system on his roof. And, by the way, we used something BETTER than a micro inverter for his system – read on to find out. Also you can Click Here to check out this customer’s testimonial video.

Why was the above customer quoted such an undersized product? Here’s a little recent history… When the 250-watt micro inverters hit the market, the 215’s became dirt-cheap. For some companies that had an overstock of 215’s, they just had to sell through them and hope that nobody caught them. For others, it was a way to make a little extra profit – dirty profit in my opinion. However, even with the 250-watt micros there was still a clipping problem. With panels now producing 265 watts or more, you were still loosing power. Today many solar companies still lead in with 250-watt micro inverters. They try to say its “no big deal” and try to make it make sense, but as a solar professional I can tell you that it does not make sense and there is NO REASON to use undersized micro inverters.

SolarEdge Inverter SystemSo here is the best part, micro inverters are not the best technology on the market. Several years ago, an Israeli company called Solar Edge came out with the world’s first hybrid system. It had all the power balancing benefits of a traditional string inverter, and panel level conversion capabilities. So the best of both worlds! This meant if you had the same 20-panel system described above, and one got shaded, you would loose only one panel. However, unlike the older micro inverter systems, the other 19 panels could increase either their voltage or current to still produce the same amount of power as the original 20 panels. Studies have shown that these hybrid systems are up to 25% more efficient in shaded situations.

In addition, the Solar Edge system can convert up to 300-watts per panel for residential systems, and even higher on commercial systems. Meaning no power loss (clipping). Sweet, Sweet, and Sweet again!!!

So going back to my cell phone analogy. Since hybrid Solar Edge system costs the same as the other systems, there is no reason to even use the older antiquated technologies. We don’t.

 

Article By: Brad Stoler ~ Solar Consultant/ Sales Manager, Rayah Solar

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