2. Air conditioning: 9 in 10 new homes have it
On average, Americans spend $2,000 a year on energy bills, over half of which goes towards heating and cooling homes, according to the EPA. How do we do it? Hereâ€™s a breakdown of energy sources for 2010:
Natural gas: 57.0 million homes (about half)
Oil: 8 million homes
Wood: About 2.2 million housesâ€“ less than 2 percent
Solar: 38,010 homes
But the biggest change since the 1970s is air conditioning. In 1974, four years after the inaugural Earth Day, 48 percent of newly built single-family homes had air conditioning. By 2010, that had climbed to 88 percent, causing a big surge in electricity use.