Abstract: The current theoretical foundation of the electricity spot market was established when the proportion of renewable energy was very low. The “time-of-use trading” assumption that the theretical foundation relies upon is unable to adapt to the new situation where the renewable energy is increasingly dominant and the regulation demand is growing in new power systems.Therefore, this paper abandons the basic assumption of “time-of-use trading” and proposes the power curve as an organic whole for trading, exploring the product form and its formation mechanism. Firstly, the forms of products in the “time-of-use trading” and the “holistic trading” proposed in this series of papers are analyzed and compared, revealing the fundamental reason why the assumption of homogeneity in power goods across different time periods in “time-of-use trading” does not hold true in practice.Secondly, from the perspective of market organizers, the nature and formation process of substitute power products are explored. It is pointed out that electricity has not only production and usage value but also balancing value, and the concepts of “substitute energy” and “regulating energy” are defined to characterize and quantify these two values, respectively. Furthermore, from the perspective of market entities, aiming to minimize the formation cost of substitute power products, a method for market entities to autonomously optimize the formation of substitute power products is proposed. It further notes that market entities can complement and aggregate to form substitute power products, adapting to the entry of a vast number of new, decentralized market entities.Finally, a case demonstrates the formation process of substitute power products in terms of quantity, quality, and price, analyzing the key factors affecting the formation cost of substitute power products. The formation process of substitute power products represents a shift for market entities from a planned “passive provision of flexibility” to a market-oriented “active provision of flexibility”, and it is also a process of exploring and enhancing the regulation capacity of systems.