To mark Earth Day, Social Explorer takes a look at trends in home heating fuels. Environmentalists have focused on energy sources and usage for decades, and the changes in fuel types offers some insight into the US's approach to home energy.   

Earth Day began in 1970, so we'll compare home heating fuel types from then to the present using data from the 1970 Decennial Census and 2015 five-year American Community Survey.

The following chart, built with Social Explorer's soon-to-be-released charting tools, shows changes in heating fuel types from 1970 to today.

As the chart reveals, the number of homes using gas, fuel oil and coal/coke/wood decreased, while electricity increased greatly. While gas is still the most popular home heating fuel, electricity is now number two.

As the following pair of maps illustrate, these home heating fuel types vary greatly by region. Many areas in the South and Pacific Northwest that used to depend on fuel oil and kerosene now use electricity.

Today, solar energy represents a small portion of home heating fuel–Just 0.1 percent of occupied housing units use solar energy. The top states/territories with solar energy are the notably sunny Hawaii (2.3 percent), Puerto Rico (0.5 percent) and New Mexico (0.3 percent).