It's actually a bit more complicated than that. Solar irradiance refers to the power per unit area of ground. Which is affected strongly by the angle of incide

It's actually a bit more complicated than that. Solar irradiance refers to the power per unit area of ground. Which is affected strongly by the angle of incidence of sunlight. You don't typically mount solar panels facing straight upwards, but rather pointing at the sun, so this has little effect. While you'll require more land to gather a given amount of solar power as you go further from the equator, you don't need more solar panels. There is also some effect due to the length of atmosphere the sunlight needs to shine through though.