The quality of the electrical supply has a direct impact on the correct function and operation of equipment connected to the public electricity supply network. There is an expectation that devices will operate as designed and that equipment lifetime should, statistically, be close to the designed value. The reliability of the network is generally assumed to be high enough so as to not cause unacceptable issues with regard to loss of production or loss of functionality. Quantifying the cost to the consumer when the supply power quality or reliability are not as expected is an important metric and can be used as business case to justify expenditure in order to improve the supply network. This paper explores the research associated with quantifying the cost of reliability and power quality. Several power quality disturbances are investigated and possible methods of quantifying both the effect and cost are presented. Due to the complex nature of equipment performance with regard to power quality, there is a need for extensive research in order to develop a generalised approach to lifetime and cost evaluation.