The clearance space needed around a hot water heater is dependent upon whether the heater is a gas or electric model. Twenty-four inches of service clearance in front and two inches on the back and sides is recommended for gas water heaters, whereas electric heaters do not require minimum clearance.
Unlike other heating devices, electric heaters do not require a minimum clearance. However, many electrical equipment codes do recommend the provision of a 30 inch working space on the front and sides of the heater to allow for examination, adjustment or maintenance of the electrical equipment. The National Electrical Code also recommends a three foot clearance in front of electrical equipment and a minimum headroom requirement of six feet.