Fuel poverty is a condition associated with the inability to afford sufficient energy services in a home, especially heating. There is no single standardised process for defining or measuring fuel poverty. Each different method used in research or policy presents biases, resulting in different numbers of affected households with implications for interventions. This systematic literature review aims to summarise the patterns and trends in the indicators and variables of fuel poverty found in relevant publications, as well as the prevalence of associated issues. This study analysed the strengths and weaknesses of the key indicators and variables, showing their biases and opportunities for improvement. The eighty-four publications analysed were selected according to the most relevant results found on Google Scholar searching for definitions and indicators of fuel poverty/energy poverty/energy hardship. The prevalence of relevant themes was identified using NVivo. Understanding the background and the strengths and weaknesses of common indicators and variables of fuel poverty can help develop efficient and effective policies and interventions.