## 1 Introduction
However, several countries have implemented various policies to support CHP considering the advantages of CHP. The UK is implementing a policy to exempt climate change contributions for high-efficiency CHP. Japan has established a roadmap with the goal of expanding CHP power generation to 5 times the level of 2010 by 2030. In the US, funding for some of the project's costs is supported when installing high-efficiency CHP, and some states offer tax-free benefits when operating CHP. The DHS produces heat from a specific sized centralized heat production facility and then sends the heat to the users through an underground heat transport pipeline. A CHP plant, which is a facility that produces electricity and heat simultaneously, is mainly utilized to produce heat in DHS. The use of CHP significantly increases energy efficiency compared to producing heat and electricity separately. According to the United States Environmental Protection Agency [4], energy efficiency is 51% when producing heat and electricity separately, while energy efficiency is 75% for CHP, which produces heat and electricity at the same time. In other words, DHS is energy efficient. Therefore, energy consumption of DHS is less than that of IHS, and DHS has the advantage of reducing air pollutant emissions and abating greenhouse gas emissions [5; 6; 7; 8; 9; 10]. In addition, CHP is equipped with a device for air pollution reduction, so there are fewer air pollutant emissions such as sulfur oxides, nitrogen oxides, and particulate matters from CHP than from individual boilers [11]. Furthermore, DHS can provide convenience to the consumer, because DHS does not need extra space for the installation of an individual boiler [12; 13]. IHS, on the other hand, is a structure that supplies fuel to the individual boiler of users through a gas pipeline network. The individual boiler is convenient to use because it allows the user to operate and stop the boiler directly. However, it is inconvenient because there is a need for separate installation space, and it requires operation and maintenance costs. In particular, consumers using IHS can suffer a great inconvenience when the boiler breaks down in winter. In South Korea, when developing new residential complexes, such as new city construction, redevelopment and reconstruction, it is necessary to decide in advance which heating system will be installed. That is, when supplying heat in urban areas with high population density, policy makers must decide whether to provide IHS or DHS to the areas. Usually, the latter has been preferred to the former because the latter uses cogeneration to dramatically reduce energy use; although both heating systems use natural gas as fuel. However, it is still unclear which system is desirable in terms of maximizing the national economic effects. Therefore, the policy makers need quantitative information about the national economic effects of IHS and DHS sectors. That is, we must reach a rational conclusion by persuading the people with scientific and objective results by analyzing the economic effects of the two sectors. This study tries to respond to these government needs. For this purpose, the input-output (IO) analysis is applied using the most recently published IO table from 2017. The IO table represents the flow of goods and services between sectors of a country's economy in a single table [14]. Using IO analysis, various economic effects related to energy can be examined [15; 16; 17; 18; 19]. In particular, this study seeks to take two approaches to applying IO analysis. First, the three economic effects, the production-inducing effect, value-added creating effect, and wage-inducing effect, for the two sectors are systematically analyzed. Second, the economic effects focusing on the two sectors are dealt with by applying techniques to specify the IHS and DHS sectors as exogenous ones. The two sectors are endogenous sectors in the original IO table.