Tankless water heater pros and cons

Short answer: a tankless water heater costs more to buy and install than a tank, uses less energy, takes up far less room, and lasts longer. Whether it pays off depends on how much hot water your house uses, whether your gas line and venting can support it, and whether someone sizes it for a North Texas winter rather than a July afternoon.

How a tankless heater works

A tank heater keeps 40 or 50 gallons hot around the clock and reheats it as it cools. A tankless unit keeps nothing. When you open a hot tap, water runs through a heat exchanger and a gas burner or electric element heats it as it passes. Close the tap and the unit shuts off.

The pros

Lower energy use

Because nothing sits in a tank losing heat, a tankless unit only burns fuel while water is flowing. The U.S. Department of Energy puts the gain at 24 to 34 percent more efficient than a storage tank for homes that use about 41 gallons of hot water a day or less, and 8 to 14 percent for homes that use a lot more. A busy household saves less in percentage terms, but it is still saving.

Hot water that does not run out

A tank empties. A properly sized tankless unit keeps going for as long as the water runs, which is what most people want from one: back-to-back showers in the morning without the last person getting a cold one.

Space

A tankless unit is about the size of a carry-on suitcase and hangs on a wall. That frees up the corner of the garage, the closet or the attic platform a tank used to need.

Longer life

The Department of Energy gives most tankless units a life expectancy of more than 20 years, against 10 to 15 for a storage tank. That assumes the unit is maintained, which matters more here than in most places (see below).

The cons

Higher upfront cost

The unit costs more than a tank, and the installation usually does too. How long the energy savings take to cover the difference depends on your usage and your gas or electric rates.

It may need a bigger gas line and new venting

A gas tankless unit burns a lot of gas for short bursts, so the line feeding it often has to be larger than the one a tank used. It also needs its own venting. Those two items are where most of the extra installation cost goes, and they are why a quote should come after someone has looked at your house.

Flow is limited by size

Each unit can heat a certain number of gallons per minute. Run two showers, the dishwasher and the washing machine at once on an undersized unit and the water will go lukewarm. In winter the incoming water is colder, so the unit has to raise the temperature further and can deliver less flow. We size for winter, not summer.

No hot water in a power outage

Even gas tankless units need electricity for their controls and fan. When the power goes out, so does the hot water. A tank will usually give you whatever hot water is already stored.

It needs yearly descaling

Collin County water is hard, and the minerals build up inside the heat exchanger. A tankless unit should be flushed with a descaling solution about once a year. Skip it and you lose efficiency first, then flow, then you get error codes. Guardian Plan members get one tank or tankless flush a year as part of the plan.

Is tankless right for your house?

It usually is if you plan to stay in the home for years, you have a gas line that can be upsized without much trouble, and your household runs out of hot water now. It usually is not if you are selling soon, your tank is fairly new, or the venting would mean major work.

Either way, we will tell you which one makes sense before we price anything. See tankless water heaters for installation and repair, or water heater installation if a new tank is the better fit. In McKinney, our tankless installation page covers sizing, permits and venting in more detail.

Genzel Plumbing is a family-owned, licensed plumber in McKinney, serving homes across Collin County since 2001. Call (972) 238-5585.