This question is part of the Super Big Solar Panel FAQ from Solar Mango, where expert answers to over 100 important questions on solar panels are provided.


Solar panels come with performance guarantees that promise a minimum performance for the entire lifetime of the solar panel.

There are two different types of such performance guarantees:

  • Standard Guarantee
  • Linear Guarantee

A standard performance guarantee essentially says that the solar panel will have a minimum efficiency % during a particular period.

For instance, a typical standard performance guarantee spec will say that the solar panel will have an efficiency of at least 90% until the end of the 10th year and minimum of 80% until end of 25th year. Now, such a guarantee only assures you the floor limit for the performance during this period, and there is no incentive at all for the panel manufacturer to produce panels that will produce more than the lower limit. Thus, under such a scenario, it could well be that your panel performs only 90% of its ideal performance for the entire duration of the first ten years; and thereafter, for the subsequent 15, it performs only at 80% for the entire duration.

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Compare this with a Linear Performance Guarantee, in which you are guaranteed a minimum performance for every year of the 25 year duration, with each year having a slightly lower performance guarantee than the previous year, the decrease varying in a linear manner. While at the end of the tenth year, the lower guaranteed limit for this also could be the same as what it was for the Standard Guarantee, in the intervening years (1-9), the GUARANTEED floor is higher than for Standard Guaranteed. Thus, over 25 years, panels will Linear Guarantee can be expected to generate significantly more electricity than panels with Standard Guarantee.

Thus, it is fairly obvious that between the two, a Linear Guarantee is superior to a Standard Guarantee. Do bear this mind when you are finalizing the selection of the solar panel.

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