Solar Review — Panels and Inverters

This week we sat down with Tim Philbin, Solar Analyst for Solaroo Energy, a local Utah solar installer, to talk about some common questions solar customers have on modules (panels) and inverters.

What is the difference between Monocrystalline and Polycrystalline solar panels?

Monocrystalline (Mono)

Mono panels have the higher efficiency rating of the two, since they are made of higher grade silicon. The manufacturing process of mono panels produces silicon wafers that look like the corners have been cut. This gives a distinct, uniform coloring and look that can be easily distinguishable from polycrystalline panels, which are perfectly rectangular with no cuts or rounded off edges.

Mono panels will also perform better in low light conditions, in higher temperatures, and last longer than poly panels. Most manufacturers that offer high efficiency mono panels like SunEdison, Solar World, and SunPower will warranty the modules for 25 years or more, and offer linear degradation protection as well.

"For Utah's climate and for most local roof designs, mono panels are a good choice," Philbin said. "They will deliver the most production for the space, the most production for the longest period of time, and will operate efficiently in our harsh climate."

Polycrystalline (Poly)

Poly panels might be the old technology, but they aren't without their own advantages. The manufacturing process of poly panels is simpler, and produces less waste.

Poly panels have been produced by melting raw silicon into square wafers since 1981, which means they have been in use for a lot longer. Because the per panel cost is less than mono panels, other applications seem to fit a polycrystalline price point and production capacity better than mono, such as solar radar speed signs, LED traffic signs, and other mobile and small use solar needs.

For these needs, maximum production is not so much a concern—adequate production and cost will fit the bill.

What are the major differences with inverters?

Enphase micro inverters

Micro inverter technology has made it possible for each individual panel in a solar array to act independently with regards to shading. For example, if half of your array is under shade, the sunny half is still producing with micro inverters. That equals more production. They tend to be a little pricier, but more production can offset the cost.

SMA string inverters

String inverters have been around a lot longer than micro inverters, so some micro inverter skeptics might say that micros haven't been on the roof long enough to fail. String inverters do have the shading problem described above—meaning that if one panel is shaded, then all on the string act as if they are shaded.

The one benefit from the SMA inverter is the ability to wire in emergency power outlets in case of power outage. Mr. Philbin notes, "We have many customers that are happy to trade a little energy production for the ability to have access to their solar power in case of emergency. There aren't any batteries for storage, but the SMA can give you a little emergency power when the sun is shining."

SolarEdge inverters with power optimizers

SolarEdge is a blend between two described above. It is a string inverter, but places power optimizers on the back of each panel that makes it act like a micro inverter with regards to shading. Mr. Philbin also adds, "Lately, many customers are choosing SolarEdge as their inverter because of Tesla's partnership with SolarEdge on the Powerwall battery. Tesla has announced that SolarEdge will be the only inverter that will be able to be retrofit with the Powerwall—and there is significant interest in the Tesla battery."

Whatever your equipment choice is, be sure to contact a trusted solar professional as your consultant. For more information on the article, click here.

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