Dear Jim: My old gas water heater is not leaky yet, but I want to replace it with an efficient, high-output model. The kids use up all the hot water in the mornings. What should I look for in an efficient model? – Joan W.

Dear Joan: Being the last one to shower in the morning and having the water get cold as you rinse is not a good start to any day. Until you install your new efficient gas water heater, install low-flow showerheads as a quick fix to stretch the hot water supply. They also save money.

There is a huge selection of gas water heater tank sizes, heat inputs and features and it can be confusing selecting the proper one for your family’s needs and budget. With today’s gas prices, and they will surely increase over time, installing a new model can save up to $100 annually.

The amount of hot water output by a water heater is represented by its First Hour Rating in gallons. This number tells you how many gallons of hot water the heater can provide in one hour. Typically most showers, cooking and washing are done within an hour or so in the morning.

The FHR includes the hot water in the tank plus how much additional cold water the gas burners can heat in one hour. A larger tank has a greater FHR as does one with a bigger gas burner. Determine how many gallons of hot water your family needs in the morning and get a water heater with that FHR.

Water heater efficiency is compared by Energy Factors. The EFs of new models range from about .50 to a high of .64. Since a larger water heater tank has more surface area than a smaller one, it loses more heat even with the same insulation thickness. Smaller ones often have higher EFs.

Design factors, such as dip tube, insulation and flue baffling, also impact the EF. An efficient dip tube causes the incoming cold water to swirl around inside the tank to increase the heat transfer from the gas burners.

Special baffling in the flue pipe, which runs up the center of the tank and is surrounded by water, also improves the heat transfer to the water. Thick injected foam insulation, between the inner tank and the outer metal skin, keeps the water from losing its heat to the utility room or basement area.

Compare the warranty periods on the water heaters as indication of quality. The best models have 10- to 12-year tank warranties. Part of the additional cost for these is a better tank lining and part for the extended time period. Dual or stainless steel reinforced anode rods add life too.

For safety, some gas water heaters have burner designs that stop the flame should volatile vapors, from gasoline, solvents, etc., be drawn into the burner. All models will have this feature soon.

Write for (instantly download – www.dulley.com) Update Bulletin No. 811 – buyer’s guide of the seven most efficient gas water heater manufacturers (45 models) listing EF, FHR, insulation level, warranty, features, and sizing-payback worksheets. Include $3 and a business-size SASE, and send to James Dulley, 6906 Royalgreen Drive, Cincinnati, OH 45244.