It's not the water heater that may be a problem. It is the fact that many times the space in front of the electrical panel is taken by "other" trades. There must be a working space clearance in front of all electrical panels 3 to 3-1/2 feet deep (depending on voltages), and as wide as the panel, but no narrower than 30 inches.
There is also a "dedicated equipment space" to avoid. The dedicated space extends from the floor to 6 feet above the panel, or to the structural ceiling, if lower, and is equal to the depth and width of the panel. Nothing above or below the panel is allowed except electrical installation stuff.
Keep out of these areas, and you are OK.