This article studies the causes of defaulting on the contractual obligations of payment for electric power and capacity by the guaranteeing suppliers and considers possible options for the improvement of the legal regulation system of the wholesale electric power and capacity market. The institution of the guaranteeing supplier has for its mission the ensuring of a reliable and uninterrupted energy supply for consumers, but, along with that useful function, the institution of the guaranteeing supplier has negative aspects as well. One fourth of the guaranteeing suppliers operate on the edge of bankruptcy and are not able to fulfill their payment obligations to other entities of the wholesale market. The compulsory requirement to enter in regulated contracts leaves the generators no opportunity to choose the most bona fide and solvent counterparty. The mechanisms to encourage payment discipline existing in the wholesale electric power and capacity market have proved to be inefficient. The electric power and capacity sellers incur global losses with, in fact, no hope to have them reimbursed in the future. As the most thoroughgoing alternative to the existing legal model of the wholesale electric power and capacity market, is, in the author’s opinion, reforming of the institution of the guaranteeing supplier with lifting of the prohibition to combine the electric power transmission and selling activities as an option. The author of this article concludes that the focus from the punitive measures for the non-payers should be shifted to application by the state of comprehensive measures to improve the situation in the segment of the insolvent guaranteeing suppliers (the power supply and power sales companies) and change their legal status.