Bridging the energy gap of India’s residential buildings by using rooftop solar PV systems for higher energy stars

The residential-building sector in India consumes >25% of the total electricity and is the third-largest consumer of electricity; consumption increased by 26% between 2014 and 2017. India has introduced a star-labelling programme for residential buildings that is applicable for all single- and multiple-dwelling units in the country for residential purposes. The Energy Performance Index (EPI) of a building (annual energy consumption in kilowatt-hours per square metre of the building) is taken as an indicator for awarding the star label for residential buildings. For gauging the EPI status of existing buildings, the electricity consumption of residential buildings (in kWh/m2/year) is established through a case study of the residential society. Two years of electricity bills are collected for an Indian residential society located in Palam, Delhi, analysed and benchmarked with the Indian residential star-labelling programme. A wide EPI gap is observed for existing buildings for five-star energy labels. Based on existing electricity tariffs, the energy consumption of residential consumers and the Bureau of Energy Efficiency (BEE)’s proposed building ENERGY STAR labelling, a grid-integrated rooftop solar photovoltaic (PV) system is considered for achieving a higher star label. This research study establishes the potential of grid-connected rooftop solar PV systems for residential buildings in Indian cities through a case study of Delhi. Techno-economic analysis of a grid-integrated 3-kWp rooftop solar PV plant is analysed by using RETScreen software. The study establishes that an additional two stars can be achieved by existing buildings by using a grid-integrated rooftop solar PV plant. Payback for retrofit of a 3-kWp rooftop solar PV plant for Indian cites varies from 3 to 7 years. A case study in Delhi, India establishes the potential of grid-connected rooftop solar PV systems for residential buildings. Techno-economic analysis of grid integrated, 3 kWp rooftop solar systems estimates a payback period from 3 to 7 years.