Tuesday, July 11, 2017

Does Solar Panel Efficiency Matter?

We love talking about solar panel efficiency!
Scientists love it. The media love it. Salesmen love it. With all the love going around, one might end up thinking… oh, I dunno, that solar panel efficiency is the be all and end all of everything.
Here at Understand Solar, we’re on a noble endeavor to find the truth. So frankly, we don’t care what everyone else thinks. We’re gonna tell you how it is.

So let’s cut straight to the chase.

If you want to get the most out of your money, you shouldn’t be worrying about efficiency. It’s NOT THAT IMPORTANT.

And as I can sense the torches and pitchforks already, allow me some internet real-estate to explain myself.

How to compare solar panel efficiency

First, what do we mean by efficiency?

Efficiency is the percentage of solar energy that a solar panel (for example: RENOGY 200 WATT 12 VOLT SOLAR STARTER KIT )converts into DC electricity. So a 10% panel converts 10% of sunlight into electricity.

Question: Panel A is 19% efficient. Panel B is 20% efficient. How much more sunlight does Panel B utilize than Panel A?

You might be tempted to say Panel B uses 1% more sunlight than Panel A and thereby that Panel B is 1% better than Panel A. But this isn’t the case.

Let’s pit Panel B with 20% efficiency against a new panel: Panel C with 10% efficiency. Under the same conditions, panel B will produce twice as much power than panel C. Clearly, the performance difference is not 10% – Panel B produces 100% more electricity than panel C.

Likewise, a 20% panel produces approximately 5% more electricity than a 19% panel. Confusing, right? Take a second a think through it all if you need to.

Okay, ready to go? Now that we’re all happy with efficiency, we can talk about why it should be low down on the list of your priorities.
The real question to ask yourself

Instead of obsessing about buying the highest efficiency panels, you should be more concerned with the solar option that produces the most watts for your dollar. In other words:

“What’s the most solar power production I can get for my money?”

Imagine you’re getting a 5kW solar system installed. System A uses 19% efficient panels for a grand cost of $15,000. System B, uses 20% efficient panels for a grand total of $20,000.

Now, both systems are 5kW; they produce the same amount of power. Note that the system with 20% panels can produce more electricity per panel, so the less efficient system will need more panels to achieve the same power production. Which system do you go for? A or B?

Let’s calculate the power you’re getting for your money.

System A: 5kw/$15,000 = $3 per watt
System B: 5kW/$20,000 = $4 per watt

Thus, you’re getting cheaper energy with system A than with system B. Provided both systems can fit on your roof, you’d be mad not to pick A.

But there’s the kicker: “Provided both systems can fit on my roof.” Well, can they?

Solar pundits these days rehash the same phrases. “If you’ve got limited space, you may want higher efficiency panels.” That’s not really a very helpful solution. It’s just too vague!

Let me be clear: IF you live in an average house, with half of your roof available for solar panels, and no giant tree in the way, going for the lowest $/watt is the way to go. If you get that with a lower efficiency panel, so be it. If a company makes it happen with a higher efficiency panel, great. The point is, for you and every other homeowner, efficiency doesn’t matter. Dollar per watt does.

Now let me prove it:

A 5kW system produces 5000W. It doesn’t matter if it’s from 10,000 panels that are 1% efficient or just 100 panels that are 100% efficient. A 5kW system produces 5kW.

A quick example to really drive the point home: Let’s say Power Plant A is 1MW and uses 1% efficient panels. Power Plant B is 1MW, and uses 20% efficient panels. Which produces the most power?

Answer: The same amount! They’re both 1MW! They produce the exact same amount of power. But Plant B’s panels are 20x better than Plant A’s, so it will need twenty times less panels to produce the same amount of electricity. Thus, Plant A will be giant, while Plant B will be modest in size.

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