**2. Literature review**

The impact of population characteristics, particularly age, density, and proportion of urban population, on residential natural gas demand is rare; this could be due to a lack of data. To estimate natural gas demand, most studies focused on price and income elasticities. Several studies, however, have shed light on the impact of population factors on overall household energy usage over the last two decades.

According to several studies, there is a link between household age and space heating energy use. That is, because elderly people are more sensitive to temperature, they consume more energy for space heating than younger people because they spend more time at home. Meanwhile, Chen et al. [6] found that age has a greater impact than wealth in a study of Hangzhou, China, and that there is a negative relationship between occupant age and residential energy usage, particularly for heating and cooling. It was discovered that older housewives are more supportive of economic conduct than younger housewives.

Kronenberg [7] observes in his study on energy consumption and greenhouse gas emissions in Germany that demographic changes, defined by a rise in the number of elderly persons, have a favorable impact on energy demand, particularly for heating.

Liao and Chang [8] used the discrete technique to estimate the space heating and water heating energy demands of senior residents in the United States using data from the 1993 Residential Energy Consumption Survey. They believe that the elderly consumes more natural gas and electricity to heat their homes. However, there is a considerable negative association between water heating energy use and age.

Ota et al. [9] found that the aging of the society has no substantial impact on residential electricity and city gas demand in 47 Japanese prefectures every 5 years between 1990 and 2010. Furthermore, population decline and the rise of nuclear households raise electricity usage while lowering city gas consumption.

Residents who live in densely populated locations (such as Dublin) use less energy for space heating than those who live in less densely populated areas. According to Elnakat et al. [10], a socioeconomic and demographic study on the residential sector in San Antonio, Bexar County, and Texas, areas with higher population density spend less energy per capita than those with lower population density. Furthermore, Arbabi and Mayfield [11] found that for increasing population densities, falling per capita gas consumption patterns are observed in a study aimed at investigating consumption behavior within the transport and home sectors in England and Wales.

Furthermore, He et al. [12] conclude, based on data from 2001 to 2011, that the greater the urban population, the greater the total natural gas consumption.

Rather than calculating natural gas demand price and income elasticities, as most research has done, the focus of this work is on demographic characteristics, particularly the elderly, population density, and urbanization rate.
