Abstract
Over the past 20 years, net-zero energy house (NZEH) construction costs have steadily decreased because of many reasons, such as technical progress, energy-saving design obligations, and dramatic cost reductions in renewable energy systems, especially solar power systems. Currently, the costs of NZEH are estimated to be about 5% higher than similar-sized houses. These additional costs are mainly for installing PV systems, which can be offset by energy saving costs. This study assessed energy performance and load matching through remote monitoring systems, and energy costs were analyzed for two-family houses. The two houses were all-electric houses and different in both size and location. A 6 kWp grid-connected PV system and 16 kW air source heat pump for space heating and domestic hot water were equally implemented. After data analysis, 100% of the energies were supplied through the PV system for 3 years, thus achieving net-zero energy. According to the Korean residential electricity tariff system, the annual electricity charges were, on average, between USD 105.1 and USD 121.4 after adding demand charges and value-added tax for import electricity charges. The energy cost reduction rate, compared to the same house without a PV system, was about 95%, and the simple payback period of the 6 kW PV system in NZEH was about 6 years. In addition, the annual load cover factor and supply cover factor as load-match indices between electricity generation and the load were in a range of 0.39–0.49 and 0.37–0.42, respectively.
Highlights
The past 20 years have seen considerable progress in the development of energyefficient buildings that significantly reduce energy usage
Various incentives have been provided for net-zero energy buildings (NZEB) and renewable systems, such as relaxation of building standards, acquisition tax reductions by up to 20%, 70% subsidy for the installation of BIPV and fuel cells, and 50%
If additional construction costs are offset by energy-saving costs, NEZH could increase its competitiveness
Summary
The past 20 years have seen considerable progress in the development of energyefficient buildings that significantly reduce energy usage. Since 2020, the Korean government has required net-zero energy by law for new public buildings with a total floor area of over 1000 m2 , and from 2025, the scope will be expanded to include public buildings with over 500 m2 , as well as private buildings. For this reason, the building energy-saving design standard has been strengthened further since 2018. A total investment of EUR 6164 is required to install a PV system without reinforcing the insulation performance of the house, and the payback period is 11.7 years. The findings provide actual cost–benefit information of NZEHs, which are in the interests of different builders, engineers, and architects
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