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This paper presents the details of the output and efficiency of the annual performance of building-integrated solar energy systems for a solar water heating system and solar photovoltaic (PV) modules of a demonstration near-zero-energy solar house that was constructed on the campus of the Korea Institute of Energy Research. The thermal systems installed in the house were a solar water heating system with building-integrated solar collectors for water heating and for part of the space heating, and a ground-coupled heat pump for space cooling and part of the space heating. Solar PV modules were installed on the roof of the house. The performance of these systems was monitored for more than 1 yr. The annual efficiencies of the building's integrated solar collectors and solar PV were 22.8% and 10.9%, respectively. The total annual solar fraction of the solar heating system was 69.7%, with an annual solar heat production of 248 kW h/m 2 . This paper also focuses on the efficiency of the house's solar storage, based upon intentionally varied drainage of hot water from the storage tank. It was found that the thermal loss from the solar storage tank has a strong functional relationship with the thermal demand of the solar storage tank per unit volume. For example, when the hot water consumption was reduced by half during September, the thermal loss increased to more than 70%, which would otherwise have been around 30%. V C 2014 AIP Publishing LLC. NOMENCLATUREA scol surface area of solar collectors (m 2 ) A spv surface area of solar PV system (m 2 ) c 1 scaling coefficient of thermal loss equation model of thermal storage tank c 2 power coefficient of thermal loss equation model of thermal storage tank G scol monthly average of solar irradiance onto the collector surface area (kW h/m 2 ) G spv monthly average of solar irradiance onto the solar PV modules (kW h/m 2 ) Q scol monthly average of collected heat amount from solar collectors (kW h) Q sol annual heat delivered by solar heating system to the heating demand (kW h) Q st,demand thermal demand including domestic hot water and space heating (kW h) Q st,loss thermal loss from the solar storage tank (kWh) SF sol annual solar fraction of solar heating system V st volume of solar storage tank (m 3 ) W spv monthly average of generated electric energy from solar PV system (kW h) g scol monthly average of collector efficiency g spv monthly average of efficiency of solar PV system a)

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