Vietnam has recently seen a remarkable solar photovoltaic (PV) boom, the first stage of a major and rapid energy transition in the country. The country’s solar PV capacity increased from only 86 MW in 2018 to 4,750 MW in 2019 (Figure 1). With this, Vietnam passed Thailand to have the largest installed capacity for solar power generation among members of the Association of Southeast Asian Nations (ASEAN) (Do et al., 2020). By the end of 2020, its installed solar PV capacity reached about 16,500MW, around one quarter of the country’s installed power capacity (Nhan Dan, 2021).

Understanding how electricity demand responds to the ambient temperature is critical for the safe and efficient operation of the power system. Examining an extended series of daily electricity records from 2011 to 2020, we find that there is a significant nonlinear temperature-electricity load response approximating a cubic function of the temperature or the cooling degree days in the two major power subsystems in northern and southern Vietnam.