As of March 2015, there are no known manufacturers that make 20-inch wall ovens, reports HGTV. The standard wall oven sizes available from most major appliance manufacturers are 24 inches, 27 inches and 30 inches.
Wall ovens are generally available as single or double oven models, and they differ in terms of function, capacity and power source. Frigidaire, GE and KitchenAid are among the top-rated wall oven manufacturers in the country, according to Best Reviews. KitchenAid manufactures a 24-inch stainless-steel gas wall oven that comes with the option of convection cooking. Another popular model is the Summit 24-inch single-wall oven, which is able to run on either natural gas or propane gas. Double-wall ovens, such as the Maytag CWE5800AC, are also manufactured in the smaller 24-inch size, notes Consumer Search.
Wall ovens come with a range of variable features, depending on the size and brand of the oven. Larger capacity wall ovens as well as those that feature convection heating and specialist functions tend to be more expensive. The vast majority of the larger wall ovens are designed to run off an electrical power source rather than natural gas, making the smaller 24-inch models a good option for natural gas users.