4.2 billion.
That's how many rooftops you'd have to cover with solar panels to displace a cubic mile of oil (CMO), a measure of energy consumption, according to Ripudaman Malhotra, who oversees research on fossil fuels at SRI International. The electricity captured in those hypothetical solar panels in a year (2.1 megawatts each) would roughly equal the energy in a CMO. The world consumes a little over 1 CMO of oil a year right now and about 3 CMOs of energy from all sources. Read the full story from News.com.