What is the appropriate equation?

Question

My college’s average electric power consumption is about 2 MW. What area of 15%-efficient photovoltaic modules would be needed to supply this much power during a summer month when insolation on the modules averages 225 W/m²? Compare your answer with the area of the college’s football field (55 m × 110 m overall).

Answer 1

This is a labelling problem (Everything is proportional). Start with an extensive variable to figure out how much of things you need... In your case it is the college's power consumption:

2 MW (1000W/MW)(100W required at solar array/15 W obtained for usage)(1m²/225 W ) = Area of solar array.

Compare that to (55m)(110m) = A of football field.

Good luck