The 2015 study represents the 14th iteration of the RECS program. First conducted in 1978, the Residential Energy Consumption Survey is a national sample survey that collects energy-related data for housing units occupied as a primary residence and the households that live in them. Data were collected from more than 5,600 households selected at random using a complex multistage, area-probability sample design. The sample represents 118.2 million U.S. households. The 1st version of the 2015 RECS microdata file, released in April 2017, reflected preliminary household characteristics data. The file was updated in October 2017 (Version 2) to include additional square footage and household energy insecurity data. The file was updated again in May 2018 (Version 3) and included final household characteristics data, as well as final consumption and expenditures data. The final version of the microdata file was updated in December 2018 (Version 4) and contains wood consumption variables, as well as additional weather and climate-related variables used in the end-use modeling process.