When you think about it many if not most people never really pick their first water heater it is usually picked for them by a previous home owner.That may also explain why when a water heater fails the response from most home owners is just put back what they had before. This is not really sound advice since the parameters for selecting a water heater are really quite reasonable. The criteria are roughly these: 1- the number of people in the home, 2- the number of bathrooms in the home, 3- how many people will be showering or bathing at the same time, 4- what outlet temperature will you be setting the water heater at, and 5- how fast do you deplete a full tank of hot water. Now let’s get a few things out of the way.
If you are a single person, a family of two parents and one or two small (ages 1 month to 6 years), children, or a couple without children a tankless water heater may be an ideal answer for you. That statement is predicated on how fast you use hot water, and how many use more than one hot water item in the house at the same time. Tankless water heaters are governed by allowing the water to heat as it moves through the heat exchanger. That being the case you may have to structure your lifestyle to use water at a rate that is compatible with the ability of the tankless to keep up. If you are a large consumer of hot water all at once or with multiple items running at the same time a tank style unit is probably better suited to your needs. There are tanks with efficiency ratings running anywhere from 65% efficient to 96% efficient. They range in capacity from 40 gallons to 100 gallons for the residential market in gas, and similar sizes for electric models. Efficiencies are based on several things, but equally important is proper gas line size, and flue considerations. Most important from a manufacturer’s point of view is that you do not continually draw the tank from hot to cold depleting the tank too fast. This causes the tank to condense while the very cold tank of water is being heated. Condensation is corrosive and as such attacks the steel tank from the outside and causes the tank to fail sooner than it needs to. It can also cause the flue to plug up do to the condensation on the tank flue walls causing rust which can build up and block the flue. These things are seen all to frequently. Your best bet is to check efficiencies, styles (tank or tankless), and then discuss with a licensed plumbing contractor what you like and if it would be a good fit for you. Most models and manufacturer’s are pretty standard in their offering. The real rubber meets the road in the application. That can be as varied as people are different.