This study analyzes the impact of demographic changes on greenhouse gas (GHG) emissions from household consumption in South Korea and projects these changes through 2050. Achieving carbon neutrality requires fundamental transformation across economic and social systems, including household consumption patterns, alongside production-side changes. South Korea's rapid demographic transition is expected to significantly alter household structures by 2050. Using data from Statistics Korea's Household Income and Expenditure Survey for 2019, we analyzed consumption patterns across 19 household types categorized by household head age and household size and constructed a hybrid input-output table to calculate GHG emission coefficients. The analysis incorporated household projection scenarios to forecast emission changes through 2050, comparing results with South Korea’s 2030 NDC and 2050 carbon neutrality targets. Results show that aging households exhibit increased expenditure on carbon-intensive goods such as electricity and heating fuels, while single-person households demonstrate higher transportation-related emissions. Projections indicate that GHG emissions will peak around 2023 earlier than the peak in household numbers and decrease by approximately 7% by 2050 due to combined aging and downsizing effects. However, this reduction is insufficient to meaningfully contribute to South Korea's climate targets, demonstrating that demographic transition provides only limited support as a “supplementary driver” rather than a “primary driver” of GHG reduction. The findings emphasize the need for aggressive additional reduction policies beyond natural demographic effects, along with targeted interventions involving energy efficiency measures for aging households and sustainable mobility solutions for single-person households.