Tag Archives: Rooftop Solar

How Much Land Would it Take to Generate All US Electricity With Solar Alone?

An in-principle calculation demonstrating how little land is really needed

Renewable energy resources are more diffuse than concentrated fossil energy, requiring wind farms spread o’er many leagues, and array upon array of solar panels. But is this a fundamental barrier to employing renewables at scale, as some would have you believe? The answer is nay, and it can be quickly seen from some back-of-the-envelope calculations (and with the assistance of some pretty maps), that no more than 7,000 square miles of photovoltaic panel surface area would be needed to generate 100% of US electricity. This is less than 0.2% of the contiguous US land area, and a small fraction of urban area in the US.

This demand could be satisfied with existing rooftops and other impermeable surfaces, such as parking lots. And of course, no all-renewable portfolio would actually be 100% solar, but this exercise shows that land area is not a limiting factor in scaling solar.

To inform our calculations, let us first introduce some fundamentals concerning solar resources…

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From 17,000 kWh/year to less than zero: my experience with energy-efficiency and rooftop solar in Mesa, AZ

I wrote several hundred pages of a book that amounted to exhorting people to alter their own habits of residential energy consumption (turn down the heat, you rogues!), as well as upgrade their built environment  (e.g. insulate the attic) and appliances, or even, *gasp*, add solar to their roofs.  All this because the numbers, at least in the abstract, showed that such banal acts of conservation (not counting solar) can reduce the carbon footprint of residential energy use by at least 30-50%, from a baseline average of about 12 metric tonnes (1 tonne = 1 metric ton) of CO$_2$-equivalent (CO$_2$e).  But a demonstration of how, over the course of roughly 5 years, the net energy use in my house actually fell progressively from around 17,000 kWh of electricity per year down to less than zero (net) seems in order.

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