Abstract The solar lease business is a recent market trend that has been introduced in many countries. An example is the U.S. solar lease payment (LP) business, which is a payment facility for leasing the solar PV system, where the customers pay a certain amount to a third-party company. In the solar lease business, the profit obtained by residences and third-party companies depends on the solar LP. Several impact factors should be simultaneously considered when estimating the solar LP that guarantees the profitability of the business for both sides. This study aimed to develop a model for determining the optimal solar LP in the solar lease business for residences and third-party companies. A genetic algorithm was utilized to solve the trade-off problem, among the many factors involved. The optimal solar LP was provided according to two categories: (i) the electricity generation rate by region; and (ii) the electricity consumption rates of multi-family housing complexes. In terms of the region, the optimal solar LP depended on the electricity generation rate, and the difference between the highest and lowest monthly solar LPs per unit was US$0.30. In terms of the electricity consumption rate, the optimal solar LP depended on the electricity consumption rate and the number of units, and the difference between the highest and lowest monthly solar LPs per unit was US$3.14. The developed model makes it possible for the government to suggest the optimal solar LP for promoting the solar lease business, and to develop a solar PV system.