Cost to Replace a Tank Water Heater With Tankless

Swapping a tank for a tankless water heater is a bigger job than replacing a tank with another tank. Angi says a conversion can take about twice as long as a standard swap, and lists conversion labor at $150 to $2,500. The total depends on what your house already has.

The pieces of a conversion

You will not need every line. A gas home with an adequate gas line may only need new venting; an electric home may need a new circuit or panel.

Why gas conversions cost more

Gas tankless heaters burn more gas at once than a tank, so the existing gas line may be too small. HomeGuide also notes that the old tank's vent cannot be reused. Angi lists gas line work at $260 to $820, rising to $1,500 when switching from electric to gas.

Why electric conversions can need a new panel

An electric tankless unit draws a large current while it heats. Angi puts a new line and sub-panel at $500 to $1,000, with total wiring up to $2,300 in some homes.

Total installed price

Once the upgrades are included, HomeGuide puts a whole-house tankless install at $1,400 to $3,000 for electric, $1,600 to $4,500 for propane and $2,100 to $5,600 for natural gas. Full details: tankless water heater cost.

Is the conversion worth it?

HomeGuide reports annual operating costs of $220 to $480 for gas tankless compared with $250 to $420 for a gas tank, and $340 to $540 for electric tankless compared with $530 to $600 for an electric tank. It estimates the extra investment can be recouped in 3 to 7 years and lists a tankless lifespan of 15 to 20 years.

Questions to ask in quotes

• Does the quote include gas line sizing, venting and electrical work, or only the unit and labor?
• Is the unit condensing or non-condensing? HomeGuide says non-condensing units cost about 25% less to install but cost more to run.
• Who pulls the permit, and is the haul-away of the old tank included?

Why the switch costs more than a straight replacement

Replacing a tank with another tank is mostly a swap. Switching to tankless usually means changing the infrastructure around the heater:

• Gas line size. Gas tankless units need much more gas at full fire than a tank heater, so the gas line or meter may need upsizing.
• Venting. Many gas tankless units need new stainless steel or PVC venting instead of the old metal flue.
• Electrical. Electric tankless models draw a lot of power and often need multiple heavy breakers and a larger electrical service.
• Water connections and mounting. The unit hangs on the wall, so new piping, valves and a mounting location are needed.

What you gain

• Hot water on demand without a tank running out.
• More floor space, since the unit mounts on a wall.
• Lower standby heat loss, because there is no tank of water kept hot all day.
• A typically longer service life than tank heaters, with regular maintenance.

What to weigh

Tankless heaters cost more to buy and install. They also need periodic descaling, especially with hard water, and a single unit may struggle if several showers and appliances run at once. Sizing by flow rate and temperature rise matters more than tank size.

Questions to ask the installer

1. Will my gas line, meter or electrical service need an upgrade?
2. What venting will be used, and where will it exit?
3. Is the unit sized for my household's peak hot water demand?
4. Does the quote include isolation valves for future flushing?

In Texas

Incoming water in Texas is warmer than in northern states for much of the year, which helps a tankless unit reach the set temperature. Hard water in many Texas cities, however, makes regular descaling important to keep the heat exchanger working well.

How long the conversion takes

A straight tank-for-tank swap is often a half-day job. A tankless conversion usually takes a full day, and longer when a new gas line, a new vent route or an electrical panel upgrade is needed. Electric conversions may need an electrician as well as a plumber, and in some cities each trade needs its own permit and inspection.

Where to mount the new unit

A tankless heater hangs on a wall, which frees up the floor space the old tank used. Gas units can be mounted inside, where they need a vent to the outside, or on an exterior wall in mild climates, which can avoid running vent pipe through the house. Placing the unit close to the bathrooms and kitchen shortens the wait for hot water at the tap. Moving it far from the old tank's spot adds piping and labor.

Hot water behavior to expect

Tankless heaters change how hot water feels:

• Endless, but at a flow limit. You will not run out, but each unit can only heat so many gallons per minute. Running two showers and a washing machine at once can drop the temperature on a unit that is too small.
• Minimum flow. Very low flows, like a trickle at the sink, may not trigger the burner.
• Cold-water sandwich. If you turn the hot water off and on again quickly, you may get a short burst of cooler water while the unit fires back up.

A recirculation pump or a model with a small built-in buffer tank can reduce the wait and the cold bursts.

Maintenance after the switch

Tankless heaters need periodic descaling, especially in hard water areas. Ask the installer to fit isolation valves, which make flushing quick and much cheaper. Without them, every maintenance visit takes longer.

Warranty

Tankless warranties often split the heat exchanger and the parts. Ask about both, and whether descaling is required to keep the warranty valid.

Sources

1. Angi: How Much Does Water Heater Replacement Cost? (updated Jul 20, 2026)
2. HomeGuide: How Much Does a Tankless Water Heater Cost? (Jan 2, 2026)