Restrictive covenants are not considered illegal, but restrictions that are particularly exacting have been found to limit the ability of an individual to do business. In these cases, some courts have found a specific restrictive covenant agreement not to be valid. That is, the court in question would not hear the case.
1 Because tankless water heaters require a 220V/240V electrical outlet or larger gas pipes than found in an average home plus a stainless steel ventilation system, installation can add $1,000-$3,000 or more, bringing total costs to $1,800-$4,500. A central tankless water heater providing hot water for an entire house can cost $800-$3,000 or more, depending on gpm capacity and whether it's gas or electric, plus features like a safety temperature lock or a remote control.
A traditional 50 gallon water heater with a 12 year warranty retails for $559 at my local Home Depot. I would spend an extra $868 to buy a tankless water heater, and at least an extra $500 in installation costs, making this unit cost at least $1,368 more than a traditional water heater.