Steam-assisted gravity drainage (SAGD) is the method of choice to extract bitumen from Athabasca oil sand reservoirs in Western Canada. Bitumen at reservoir condition is immobile due to high viscosity and its saturation is typically large that limits the injectivity of a steam at in-situ condition. In a current industry practice, steam is circulated within injection and production wells. Operators keep the steam circulation till mobile bitumen breaks through the producer and communication is established between the injector and the producer. The "start-up" (or "circulation") phase is ranging between three to several months. A variety of processes are used to minimize time of start-up phase such as: electro-magnetic (EM) heating either induction (medium frequency) or radio frequency (RF) ranges. Knowing the hot-zone size formed by steam circulation and benefit of simultaneous EM-heating techniques help better understand the start-up process and how to minimize the start-up duration. The aim of the present work is to introduce an analytical model to predict start-up duration for only steam circulation and also for with EM-heating. The results obtained from this study reveal that induction slightly decrease start-up time for frequencies smaller than 10 kHz, and it can reduce start-up time to 30% of original steam circulation for 100 kHz frequency.