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Through Laplace transform and Stehfest numerical inversion, this research established a mathematical model for constant temperature electric heating of dual-horizontal-well steam-assisted gravity drainage (SAGD) start-up. To verify the model, a finite element simulation based on a typical SAGD block was completed, which proved the excellent agreement between the model solution and simulation results. Moreover, by means of superposition principle, underground temperature distribution and energy-related parameters during the multiwell operation were obtained, as well as a computational method targeted at quantifying the conserved energy, water and fuel of electric heating against steam heating. A parametric sensitivity analysis of electric heating was undertaken, which proved that the start-up effect is most sensitive to heating temperature, featuring a nonlinear negative correlation. Additionally, start-up effect is positively linear-correlative to porosity, and negatively linear-correlative to wellbore radius and oil saturation. The proposed model can be employed to predict key indexes such as underground temperature distribution, energy-consumption parameters, and accumulated conserved amounts of energy, water and fuel versus steam heating. Under a specified terminal temperature, temporal and energy quantities required by the start-up can also be determined. Key words: dual-horizontal-well SAGD, constant-temperature electric heating, underground temperature distribution, energy consumption, energy conservation, water conservation, fuel conservation