The Low Income Home Energy Assistance Program (LIHEAP, pronounced "lie" "heap") is a United States federal social services program first established in 1981 and funded annually through Congressional appropriations. The mission of LIHEAP is to assist low income households, particularly those with the lowest incomes that pay a high proportion of household income for home energy, primarily in meeting their immediate home energy needs. The program, part of the United States Department of Health and Human Services (HHS), is funded by grants appropriated from the federal government.

Weatherization funding peaked to over 500 million dollars in 2009 and by 2014 had decreased to about 300. In 2014, it served over 80 thousand households in over 40 states, out of over 5 million in the LIHEAP program. In total since 1976, weatherization assisted over 7 million low-income households, which received free home improvements worth an average of about $5,000. The most common measures were furnace replacement, attic and wall insulation, and infiltration reduction. A random trial in Michigan estimated that the measures reduced energy consumption by 10-20 % on average.