The poor quality of electrical power in Brazil has led to an increase in the sales of power conditioning equipment such as uninterruptible power systems (UPS) to supply a voltage wave shape without distortion or interruption. However, there are indications that the average performance of the UPS equipment available in the Brazilian market requires some improvement. Information about the energy-related behaviour of UPS units is scarce. In this paper, we estimate and analyse the installed capacity of UPS units and assess their power consumption, losses and impact on the power quality in the electrical system. The analysis is performed through energy efficiency and power quality measurements performed on UPS units that are commonly available in Brazil. We estimate the energy conservation potential of the UPS. The results of assessments strongly support the need for public policies for energy efficiency and power quality improvements, particularly the labelling of UPS units and the introduction of minimum performance standards for UPS devices. (C) 2011 Elsevier Ltd. All rights reserved.