Posted on June 27, 2013 Your new water heater should satisfy your hot water needs and use as little energy as possible. The standard size for a residential water heater is 40 or 50 gallons. The capacity of a hot water heater should be based on the number of occupants and the peak hour water demand, not on the size of the house. The heater should provide enough hot water at the busiest time of the day. Also consider the number of plumbing fixtures you have in the home. The more sinks you have, the greater the demand for hot water. Also consider extraordinary hot water demands, like hot tubs. Call Deer Valley Plumbing Contractors, Inc. at (602) 832-8418 to install today.