The European Union obliged the member states to introduce monitoring and control tools in order to improve the quality of provided transmission services and to guarantee the contracted amount of energy to end users. However, the EU has left the member states the freedom to create and implement compensation tools, enabling customers to claim their rights arising from non-compliance by transmission companies with the provisions of distribution agreements. The introduction of quantitative energy monitoring and an appropriate compensation mechanism is of great importance not only for end users but also for distribution companies. For end users, this would be a tool to enforce their rights against transmission companies, while transmission companies would gain a tool to control and manage both legal and financial risks. The aim of this study is to analyze discount as an example of a guarantee instrument in the field of the consumer’s right to energy of an adequate quality based on the Polish example supported by a systematic legal review. In the EU, discount is not regulated directly at the EU level; hence, it is impossible to base it on acquis and analyze it through the prism of EU regulation. In Poland, the possibility for recipients to apply for a discount for poor-quality electricity was introduced into the first version of the Energy Law in 1998, long before the adoption of Directive 2019/944 by the EU. The fundamental issues that were addressed and discussed in this paper were as follows: (1) Is the discount compensatory in nature? (2) Should it be included in the compensation due to the consumer? (3) Is it possible to reduce it when the power supply interruption results from circumstances beyond the control of the energy company (e.g., unforeseen weather conditions)?