An article in the Journal of Food Engineering, compares different ways of cooking rice - microwave, electric rice cooker and pressure cooking, with or without pre-soaking of the rice. Among the cooking appliances assessed, the electric rice cooker was the most energy efficient, while microwave cooking (the quickest method) was on a par in energy terms with pressure cooking, which is the most commonly followed method of cooking rice (note this is an Indian study where pressure cooking is common).