Tankless Water Heater Conversion Cost

National cost range

Low end

$3,500

Simple access, like-for-like

Typical

$5,500

What most jobs come in at

High end

$9,000

Upgrades, difficult access, code work

What you are actually paying for

Find the row that matches your situation. Quotes that differ wildly from each other usually differ in scope, not in price.

What moves the price

In descending order of impact. These are also the questions worth asking a contractor whose quote sits outside the range above.

1. 1

   Gas line upsizing

   A tankless gas unit may need 3/4-inch gas line where the old tank used 1/2 inch. Running new gas pipe is the most common hidden cost on a conversion quote.

2. 2

   Venting change

   Tankless gas units require category III or IV stainless venting through the wall or roof. Abandoning the old atmospheric vent and installing new vent pipe adds $500 to $1,500.

3. 3

   Electrical for electric tankless

   A whole-house electric tankless may need 120 to 160 amps of dedicated capacity — often requiring a panel upgrade. Point-of-use electric units are simpler.

4. 4

   Water treatment

   Tankless manufacturers often require water hardness below 11 gpg. A softener installed concurrently adds $800 to $2,000.

5. 5

   Unit capacity and brand

   A 6.5 GPM unit handles one bathroom. An 8 to 10 GPM unit handles a whole house. Navien, Rinnai, and Rheem are the common brands; capacity drives price.

Direct answer

Converting from a tank water heater to a tankless unit in 2026 typically costs $3,500 to $9,000 installed nationwide, with gas conversions that need venting and gas line upsizing clustering near $4,500 to $7,500 and electric whole-house units landing $2,500 to $5,000 before any panel upgrade. Infrastructure—Category III/IV venting, 3/4-inch gas pipe, water treatment, and dedicated high-amperage circuits—usually exceeds the tankless unit price on the invoice.

What each price band actually buys

Low end

Gas tankless where gas line and vent path are already adequate, exterior termination.

Typical

Gas unit with new stainless vent, minor gas pipe, flush mount, permit.

High end

Long gas run, interior vent routing, water softener, electric tankless plus 200A panel work.

Labor vs materials

Typical split for this job nationally: roughly 50% labor and 50% materials. Crew size is usually 1–2 plumbers plus electrician if needed, across one to two days across trades.

What this price usually does not include

• Whole-house repiping or recirculation loop unless scoped
• Major drywall and paint after vent routes
• Panel upgrade beyond line-item electrical (see panel-upgrade guide)
• Gas service upgrade from utility if meter is undersized
• Deck or roof repair after vent penetration
• Annual descaling service plans

Hidden costs that show up on real jobs

Regional variation

Gas conversion costs track plumber and gas fitter wages; venting complexity rises in cold climates with long interior runs. Electric conversions hinge on regional panel upgrade pricing. Use `/home/cost/tankless-water-heater-conversion/[metro]` localized figures when published, and confirm gas meter capacity with the utility before accepting a quote.

Code upgrades this job can trigger

• Combustion air and vent clearances per manufacturer and fuel gas code
• Gas shutoff and sediment trap at appliance
• Water heater isolation valves and expansion tank where closed systems exist
• Electrical disconnect for electric units
• Scale prevention or softener per manufacturer warranty terms

Repair vs replace

If your tank failed, compare a like-for-like tank replacement ($900–$3,400) to conversion ($3,500–$9,000+) on payback, not just energy romance. Conversion makes sense when you have simultaneous infrastructure projects, limited space, or high hot-water use patterns that favor endless flow. Repairing an aging tank is rarely wise; converting solely because the tank leaked without budgeting gas or electrical upgrades leads to change orders. Run gas load and electrical load calculations before signing.

Timeline and visits

Best-case gas conversions finish in one day; vent and gas line jobs often take two days plus inspection. Electric conversions may require an electrician day separate from plumbing trim.

Quote checklist — line items a fair bid should show

1. Tankless model, flow rate (GPM), and fuel type
2. Gas line size test and upsizing scope
3. Vent material, route, and termination
4. Water treatment or softener if required
5. Electrical circuit amperage for electric models
6. Removal of tank and abandonment of old vent
7. Permit and inspection fees
8. Startup, combustion analysis, and homeowner briefing on flow limits

Questions to ask before you sign

• Did you calculate peak GPM for my fixtures and size the unit accordingly?
• Will the gas meter support additional BTU load?
• What vent route will you use and who patches interior finishes?
• Is my water hardness within warranty limits?
• For electric, is panel upgrade a separate line item with load calc?
• What maintenance (descaling) interval do you recommend?

Quote red flags for this job

• Quotes tankless price without gas or vent site visit
• Omits venting change from atmospheric tank vent
• Electric tankless quoted with no amperage calculation
• Ignores simultaneous shower and appliance flow limits
• Single price without permit
• Promises same-day conversion without inventory and inspection plan

Payment schedule norms

Plumbing-heavy conversions: 20–30% deposit, progress at rough-in, balance at inspection. Coordinate electrical draw separately if subcontracted.

Seasonality

Emergency tank failures spike in winter; planning conversion during mild weather eases vent work. Utility rebates for high-efficiency water heaters may have annual caps—apply early.

Can you do it yourself?

When this cannot wait

• Tank failed and you want to switch technology rather than replace like-for-like
• Running out of hot water regularly with a properly sized tank
• Wanting to reclaim closet or garage space occupied by a tank

Common questions