Here’s a practically effortless way to clean an electric oven: First, turn the oven on, let it warm to 150° F (65°C), and then turn it off. Place a small oven-safe bowl containing ½ cup ammonia on the top shelf and a large pan of boiling water on the bottom shelf. Close the oven door, and let it sit overnight. The next morning, remove the dish and pan, and let the oven air out a while. Then, wipe it clean using the ammonia and a few drops of dishwashing liquid diluted in a quart of warm water. Even old baked-on grease should wipe right off!
WARNING: Do not use this cleaning method with a gas oven unless the pilot lights are out and the main gas lines are shut off. Never mix ammonia with bleach or any product containing chlorine. The combination produces toxic fumes that can be deadly. Work in a well-ventilated space and avoid inhailing the vapours. Wear rubber gloves and avoid getting ammonia on your skin or in your eyes. Always store ammonia out of the reach of children.