Level Of Importance #5
Why Is It Important ?
Well in reality, in most real world applications efficiency is not that important, which is why we rate it at number five on our level of importance. The term efficiency is probably one of the most misused, misunderstood terms in the solar industry that can have multiple meanings depending on which salesman you happen to be talking to at the moment.
Some manufacturers will use the term efficiency to represent power as in "the most powerful solar panels in the universe" while failing to mention their relatively poor negative tolerance ratings and high cost. When it comes to a solar system's power rating, a 5kw system is a 5kw system, no matter what the efficiency rating is. Otherwise a higher efficiency 5kW system would be rated at 5.1kW or 5.2kW and so on.
Other manufacturers will avoid the term efficiency like the plague or will manipulate their ads so that they talk about the "high efficiency" that's used in their manufacturing process or how "thin and sleek" their solar panels are or that their solar panels offers the "highest efficiency" in their class. Never mind that their product's class offers one of the lowest efficiency ratings in the industry.
So what's the truth about efficiency ? It simple, the higher the efficiency that the solar panel offers the smaller the solar panel. And since efficiencies only vary by a few percentage points from panel to panel, in most cases you are only talking about a difference of a few square inches.
So if your roof has sufficient space for the solar panels that you're considering, why pay thousands or even tens of thousands of dollars more for higher efficiency solar panels. On the other hand if you can buy solar panels that offer a higher efficiency rating at a lower price than lower efficiency solar panels, then why not.
The second truth about efficiency is that you may receive a very small advantage when operating your your panels under low light conditions. But in reality how often will your system experience low light conditions ? And again is that small advantage worth the thousands more that most "higher efficiency" solar panels garner.
When it comes to efficiency it is far more important to consider the system overall efficiency which includes the PTC rating of the solar panels and the conversion efficiency rating of the power conversion unit.
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