Less Efficient Solar Panels Produce More?

by Shawn | 6 Comments

Brad had a very good question that I thought needed to be explained in a post of it’s own.

I’m confused as to how a less efficient system (measured under PTC) could output more.

The simple answer is – if there are more of the ‘less efficient’ panels.

Solar Apples Analogy

At the supermarket, there are two types of apples for sale. They taste EXACTLY the same. There is no quality difference – only a size difference. One type of apple is big and the other is small.

  • -You can get 3 big apples for $6. The amount of apple you get is 600 grams (200 grams/big apple).
  • -You can get 4 smaller apples for $5.50 and the amount of apple is 640 grams (160 grams/small apple).

Yes, the bigger apples are more efficient – there’s more to eat per apple. But the farmer needed to spend a little more effort to get the apples bigger, so they cost a little more. The smaller apples are easier for the farmer to harvest, so they cost a little less than the big ones.

If the apples taste exactly the same, came from neighboring farms in the same delicious apple-growing region, and you only wanted to get the most apple for your buck, then the smaller, cheaper apples are better a deal.

I believe the same holds true for solar panels that are equally warrantied by their respective manufacturers.
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Less Efficient Solar Can Be Better

Efficiency only matters when space is limited. If you want to get the most output of a limited space, then you’ll want the most efficient solar panels. However, if the area available for solar isn’t limited, then you can fit a few more ‘less efficient’ panels on the roof and possibly add up to more total output than the ‘more efficient’ panels.

For example, you could have 22 ‘less efficient’ panels that produce 7,100 kWh and cost $35,000. Or 20 ‘more efficient’ panels producing 6,800 kWh per year costing $40,000.

Or you could have 28 of each, but the ‘less efficient’ panels actually take up more space, but end up producing more than the ‘more efficient’ panels. They are ‘more efficient’ because they produce more in the same (or less) area, not necessarily more overall. Look at the ‘Area’ row in the chart below.

Solar Cost Comparison Chart

It’s just like the apples. Don’t let the salesman try to convince you that you should buy the big apples because there’s more per apple. Just buy a few more smaller apples and get more apple for a better price.

Now, you might be thinking that the ‘more efficient’ panels will produce ‘better’ energy. It all comes from the Sun, so there’s NO difference in quality of energy produced.

But maybe the ‘more efficient’ panels will produce more over time because they will degrade less. Ask your solar installer the details of the warranties for the panels. She’ll probably say both the ‘less efficient’ and ‘more efficient’ panels are warrantied for 90% output for 10 years, and 80% for 25 years. Until they guarantee more output overtime, that’s the same taste.

Less efficient can be a better deal.

Related posts:

  1. Solar Comparison Table
  2. Top 40 Most Efficient Solar Panels
  3. Most Efficient Solar Panels
  • Tim

    While this is true now, you dont seem to factor in that the cheaper panels take up more space and that this is a disadvantage.

    Given that the average home has only a fraction of it overall roof space actually facing the right direction and therefore suitable for solar panels, and the fact they have a lifespan of over 25 years. It might be wise to go with fewer more efficient panels now and as technology improves and prices continue to drop, you are more likely to get better bang for your buck doing a staggered installation over time rather than taking up all your roof space in one go.

  • That Guy

    No offense intended here. Just wondering where you got these numbers from.

    • The kWh came from the CSI EPBB calculator explained in my post How to Calculate Solar Output Like the Pro’s. The prices were estimated based on average per kw installation rates in CA of $6.45 for the Canadian Solar panels and $7.15 for the SunPower panels. The area was calculated using the manufacturers’ spec sheets. The rest was just math, and it was simplified for understanding. Hope that answers your question.

  • Sean

    I think this logic is great for my situation, as I have a 14 acre farm that used to be flat pastures for horses but is now just overgrown.

    So with all this open area, I can build up some support structures for a couple rows of solar panels, have it wired into my house and grid, and reap the rewards of buying less efficient panels for a lot less money, and have the higher quantity of panels put out more energy that I get to charge $$$ back to my power company.

    Since I have so much open land, I can build a less efficient system that outputs a lot more power for a comparable price to the more efficient system that fits on a small roof.

  • I agree with your article. I am an installer and can’t believe the other competitors that try to upsell the “more efficient” concept. In most cases if you have the roof space it is not worth the extra expense to invest in a high efficiency panel.

  • Bruce

    In a very limited space, not only is efficiency important but so is panel dimensions.You want as many SF of panel in that small space as possible.It is difficult to find length and width information.