Water heater enclosures can be purchased at The Home Depot, Lowe's and Amazon.com. Water heater enclosures protect outdoor water heaters from weather, damage and theft. They are usually for apartments and small homes that don't have room for a water heater tank indoors.
As of March 2015, The Home Depot sells Watts and Everbilt enclosures, Amazon.com sells Watts, and Lowe's sells Holdrite. The Watts and Everbilt enclosures come in two sizes: one for tanks up to 50 gallons and one for tanks up to 80 gallons. Holdrite has a single size enclosure that holds tanks up to 80 gallons. Enclosures may be freestanding, or they may attach to the side of a building.