Tankless vs Tank Water Heater: Which Is Right for You?
Tankless units last longer and save energy in many homes. They also cost more to install and can need a bigger gas line.
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The short answer
A tank heater is cheaper to buy and install, and it is the simplest swap if you already have one. A tankless heater costs more up front, saves floor space, lasts longer and can save energy, especially in a household that uses little hot water. The right answer depends on your gas line, your budget and how you use hot water.
According to the U.S. Department of Energy, tankless heaters can be 24 to 34 percent more energy efficient than storage tank models in homes that use about 41 gallons or less of hot water a day, and about 8 to 14 percent more efficient in homes that use a lot more. The department also gives a lifespan of 20 years or more for tankless units, against 10 to 15 for tanks.
Side by side
These are the trade-offs that matter for most homes.
| Tank | Tankless | |
|---|---|---|
| Upfront cost | Lower | Higher, and installation can add more |
| Typical life | 10 to 15 years, per the Department of Energy | 20 years or more with maintenance |
| Hot water supply | A fixed amount, then a wait to reheat | Continuous, limited by flow rate |
| Space | Needs floor space for the tank | Wall-mounted and compact |
| Energy use | Keeps water hot all day | Heats on demand |
| Installation changes | Usually a like-for-like swap | May need a larger gas line, new venting or a bigger circuit |
| Maintenance | Flush and check the anode rod | Descale on a schedule, see tankless service |
The hidden cost of switching
A tankless gas heater burns far more gas at once than a tank does, because it heats a stream of water instantly. If the gas line to the heater is sized for a tank, it may need to be upsized, and the venting may have to change. An electric tankless unit can need a large dedicated circuit that the electrical panel may not be able to supply.
These changes are why a plumber has to look at the house before quoting. See gas line installation and repair for the piping side of the job.
Questions that decide it
- How many people use hot water, and do they run several fixtures at once?
- Is the current heater a gas or electric unit, and how far is the gas line?
- How long do you plan to stay in the home?
- Is floor space in the garage or closet tight?
- Does your water leave scale, which tankless units need flushed regularly?
- What is your budget now, and what do you want to save on bills over time?
Tankless is not endless in a big household
Tankless heaters deliver hot water continuously, but only up to a flow rate. A single unit that has to run two showers and a dishwasher at the same time can run short. Larger households sometimes need a bigger unit or a second one, and that changes the cost. Ask the plumber to size the unit to your peak use, not your average use.
Heat pump water heaters
There is a third option. Heat pump water heaters move heat from the surrounding air into the tank and use much less electricity than a standard electric tank. They need space and airflow around the unit, and rebates and rules change over time, so ask about current programs. They are worth considering in a home with an electric heater and a suitable garage or utility room.
Our page on water heater installation and replacement covers all three types side by side.
If your heater has already failed
If the current tank is leaking, the fast answer is often another tank, since a like-for-like swap can be done quickly. Switching to tankless takes planning and parts. If you want tankless, it can be worth a day or two without hot water, or a temporary plan, so the job is done properly. If you are still deciding whether to fix or replace, see repair or replace first.
What daily life is like
The first few seconds can feel different. A tankless heater has to detect flow before it fires, and water that was already in the pipes cools while it waits, so you may get a short burst of cold water between two uses. Waiting for hot water to reach a distant tap takes the same time as with a tank, unless you add a recirculation pump.
Gas tankless units are also louder in the utility space than tanks, and they need a vent that is routed correctly. Ask where the unit will go and where the vent will exit.
Before you sign a tankless quote
- Does the price include any gas line upsizing, venting changes and a condensate drain?
- What flow rate does the unit deliver at our incoming water temperature?
- Are isolation valves included, so the unit can be flushed later?
- What does the warranty cover on the heat exchanger and on parts?
- Who pulls the permit and schedules the inspection?
- What happens to the old tank and its connections?
Questions about this topic
For many homes, yes, over the long run. It costs more up front, but it can last longer and use less energy. The gas line and venting can change the math.
The U.S. Department of Energy gives a lifespan of 20 years or more with proper maintenance.
Not in the usual sense, but they have a maximum flow rate. Running too many fixtures at once can lower the temperature.
Often, but the gas line, venting and electrical supply may need changes. A plumber has to check first.
Tankless is often cheaper to run in homes with modest hot water use. The savings shrink as use rises.
Related guides
Repair or Replace a Water Heater? How to Decide
Age, where the water is coming from and what the repair costs settle most cases in a few minutes.
Water Heater Permit in Sacramento County: What You Need
A same-for-same replacement usually needs a plumbing permit. Here is what the permit and inspection cover.
Hard Water and Water Heaters in Sacramento: What to Know
Scale is the quiet cause of many heater problems. Here is how it forms and what to do about it.
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