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Brain Teaser: Solar panels

Anonymous A asked on May 14, 2018

Greetings everyone! A short time ago I have been asked a question to evaluate the number of solar energy panels (1 sq. meter each) can be placed in France? (explain assumptions.)
And how many of them are needed to cover all demand for energy in France.
How would you answer these questions?

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Sidi
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replied on May 14, 2018
McKinsey Engagement Manager & BCG Consultant | Interviewer at McK & BCG for 7 years | Coached 90+ candidates secure MBB offers
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Hi Anonymous,

first of all - this is not a brain teaaser, but an ordinary estimation question! Here is a high-level approach:

I would start with the second question, because it is most straight forward:

1. Clarify the required generation capacity in France (a Gigawatt figure)

2. Clarify the generation capacity per square meter of solar panel

3. Divide 1 by 2

Regarding the first question:

1. Brainstorm a list of facilities where solar panels can be installed (of course roofs, but there might be additional areas)

2. Estimate a maximum percentage for each kind of installation facility that can be used for solar panel installations

3. Estimate the average installation area (in sqm) available for each facility type

4. Estimate the number for each facility type (e.g. number of roofs in France)

5. Multiply 4 with 3 and with 2 for each facility type and add up the results. This is the overall (potential) installation area of solar panels in France (in sqm). Since a panel has 1 sqm size, this is also the number of panels.

Cheers, Sidi

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