As the global push for carbon neutrality by 2050 accelerates, the building sector accounts for approximately 30-40% of global greenhouse gas emissions. Because emissions from buildings are directly tied to daily life, many countries—especially those in the EU—have prioritized reducing them as a core element of their decarbonization strategies. In South Korea, buildings contribute about 24% of total national emissions, with the share from residential buildings steadily increasing.

A particularly important trend is the surge in single-person households. In 2023, single-person household made up 35.5% of all Korean households, with projections suggesting that this figure could approach 50% by 2040. This is not unique to Korea. In major advanced economies like Sweden, Germany, France, and Japan, single-person households already comprise 30-50% of all households. In Stockholm, Sweden, they even exceed 50%, the highest proportion in the world.

Recent research is drawing global attention by identifying the rise in single-person households as a significant driver of increased energy use and carbon emissions in the building sector.

Single-Person Households Consume More Than Twice the Energy per Person 

The team tracked heating, electricity, and how water usage in 518 real households in central Seoul over a full year, recording hourly data. Using an AI-based algorithm to automatically detect occupancy, they analyzed not just raw usage but behavior-driven consumption patterns in detail.

The results were striking. On a per-person basis, single-person households consumed significantly more energy than multi-person households.

<Comparison of Single- vs. Multi-Person Household Energy Consumption (based on large-scale field measurements) >

The main driver of heating energy waste was the habit of leaving heating system running even while away from home. For example, single-person households made up of office workers or students spent most of the day outside but still consumed 43.6% of their daily heating energy while the home was unoccupied.

Single-Person Households Lives in Homes Designed for Four 

Why do people living alone use so much more energy?

The core issue is structural. Most housing is still designed and built for four-person households, with heating, electrical, and hot-water systems sized accordingly. Single-person households do not share these systems with others, meaning that even when they turn things off, standby power remains. Hot-water tanks are oversized, heating more water than a single occupant needs.

This loss of economies of scale creates a structural limitation, making it inevitable that single-person households consume more energy per person to achieve the same level of comfort and service.

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Single-Person Households Lives in Homes Designed for Four 

Why do people living alone use so much more energy?

The core issue is structural. Most housing is still designed and built for four-person households, with heating, electrical, and hot-water systems sized accordingly. Single-person households do not share these systems with others, meaning that even when they turn things off, standby power remains. Hot-water tanks are oversized, heating more water than a single occupant needs.

This loss of economies of scale creates a structural limitation, making it inevitable that single-person households consume more energy per person to achieve the same level of comfort and service.

A Paradigm Shift in Housing Design and Policy 

Prof. Doosam Song emphasizes: “This is the first study to reveal the energy consumption problem of single-person households using objective field measurements and algorithmic analysis. Previously, it was merely assumed or overlooked.”

He argues that achieving carbon neutrality will require new strategies for housing design, heating/cooling/hot-water systems, and smart control technologies specially targeted at single-person households.

Single-person households are no longer a niche or special case—they represent a global structural shift in how people live. Without tailored design and policy, reducing emissions from the building sector will face fundamental limits.

This research was supported by the Ministry of Land, Infrastructure and Transport and Korea Authority of Land & Infrastructure Safety. It has been published in the leading international energy journal Renewable and Sustainable Energy Reviews (Impact Factor 16.3) in February 2025.

※ Title: Unveiling energy inefficiencies: A study on building energy consumption in single-person households

※ Authors: Dr. Jisoo Shim (First Author), Professor Doosam Song (Corresponding Author)

※ DOI: https://doi.org/10.1016/j.rser.2025.115546