25 5/8 inches for height, 13 7/8 inches for width, and a depth of 9 7/8 inches. 
Local code requires 18 inches for the height requirement for the gas water heater installed in the garage. I want to count the 2 HWT legs as part of my 18''. I remember a gas fitter told me, 18 inches from the garage floor to the flame. Gas is used to heat water for these types of heaters. These are known to heat water in a quicker manner and also help maintain the stability of the temperature of the water. The water heater dimensions for these are: 25 5/8 inches for height, 13 7/8 inches for width, and a depth of 9 7/8 inches. There are also other dimensions that are available if you like. 3. Measure the maximum height and width space for your new water heater. Remember to also check your access door space for clearance. 4. Choose a warranty model that’s right for you. Tankless water heaters last more than 20 years, while an electric or gas water heater has a life expectancy of about 10 years. 1 Measure the height of your old water heater and buy a new one the same height so you don't have to change the length of the water, gas or electrical lines. 2  The drain valve (Photo 2) on old water heaters often clogs up. 3  If the water drains slowly, be patient. Tankless or on-demand heaters for water are also called instantaneous water heaters. There is no need to use a storage tank for these types. A good choice would be 20 inches for its height, 14 inches for its weight, and 6 inches deep. Gas Water Heater Code. Local code requires 18 inches for the height requirement for the gas water heater installed in the garage. I want to count the 2 HWT legs as part of my 18''. I remember a gas fitter told me, 18 inches from the garage floor to the flame.
https://answers.yahoo.com/question/index?qid=20100619094415AAo1fhv http://www.dimensionsinfo.com/water-heater-dimensions/ http://www.rheem.com/Products/tank_water_heaters/homeowners/ http://www.familyhandyman.com/plumbing/water-heater/replacing-a-water-heater/view-all http://www.dimensionsinfo.com/water-heater-dimensions/ https://answers.yahoo.com/question/index?qid=20100619094415AAo1fhv
measuring water heater height