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Tank or tankless: choosing a replacement water heater

When the old water heater goes, you have a few days to choose. Here is how tank and tankless heaters compare on cost, hot water, space and running costs, so you can decide before you need to.

Most people choose a new water heater in a hurry, standing in a wet basement. It is worth deciding in advance, because the choice affects your gas or electric bill for the next decade and more.

The two kinds

A tank heater keeps 40 to 80 gallons hot all the time. It is simple, familiar and comparatively cheap to buy and to install.

A tankless heater heats water only as it flows through, so there is no tank and no standing loss. It is smaller, lasts longer, and costs more to buy and, usually, a good deal more to install.

Cost to buy and install

A like-for-like tank replacement is the cheapest option. The new heater connects to the existing pipes, vent and gas or electric supply.

A tankless gas heater needs a larger gas supply line than most tank heaters, a new vent through the wall or roof, and a condensate drain on the efficient models. Those three items are where the installation cost comes from. Going tankless in a house that has never had one commonly costs two to three times a tank replacement, all in.

Electric tankless heaters are cheaper to buy but need a very large electrical supply. In many older Bergen County houses the panel cannot provide it without an upgrade.

Running costs

A tank loses heat through its walls around the clock. A tankless heater does not, and the efficient condensing models turn more of the gas into hot water. For a typical household the saving is real but modest, and it takes years to repay the higher installation cost. The saving is larger for a house that uses little hot water, because the standing loss of a tank is then a bigger share of the total.

How much hot water

A tank gives a fixed amount at full temperature, then runs out and recovers slowly. Two showers and a laundry load in a row will empty a 40-gallon tank.

A tankless heater never runs out, but it can only deliver so many gallons a minute. One model may handle a shower and a sink together, but not two showers and the dishwasher. Size it for the busiest ten minutes of your morning, and remember that incoming water is much colder in a New Jersey January than in July, which reduces the output.

Space and lifespan

A tankless heater hangs on the wall and frees up the floor. It also lasts longer, often twenty years against ten to twelve for a tank, provided it is descaled regularly. In hard water areas, that annual service is not optional, and skipping it is the usual reason a tankless heater fails early.

The middle options

  • A high-efficiency tank with better insulation and a more efficient burner costs a little more than a basic tank and cuts running costs without any plumbing changes.
  • A heat pump water heater is an electric tank that draws heat from the air around it. It uses far less electricity than a standard electric tank and there are often utility rebates. It needs a large, warmish space such as a basement, and it cools and dehumidifies that space, which many people count as a bonus.
  • A larger tank, if the real problem is running out of hot water.

Permits and installers

In New Jersey, replacing a water heater requires a permit and an inspection, and gas work must be done by a licensed master plumber. A reputable installer handles the permit as part of the job. If someone offers to skip it to save money, that is a reason to choose someone else.

Questions to ask for a quote

  1. What size or flow rate do you recommend, and why?
  2. Does the price include the permit, removal of the old heater, and any venting or gas line work?
  3. What is the warranty on the tank or heat exchanger, and on the labor?
  4. For tankless: what does the yearly descaling involve, and can I do it myself?
  5. Are there utility or state rebates for the efficient options?

To get quotes, find a licensed plumber near your town.

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