Tankless Conversion at Water Heater Replacement
Converting from a tank to a tankless during replacement costs $3,500 to $6,500 installed for gas, roughly $2,000 to $3,500 above like-for-like tank replacement. The decision is rarely about the unit itself; it is about how much gas-line resize, venting, and labour the conversion triggers. This page walks the cost lines and the cases where the conversion pays back.
The conversion premium broken out by line item
| Line item | Like-for-like tank | Tankless conversion | Delta |
|---|---|---|---|
| Unit cost | $550-$1,100 | $900-$2,400 | +$350 to +$1,300 |
| Labour (install + commissioning) | $450-$1,400 | $1,200-$2,600 | +$750 to +$1,200 |
| Gas-line resize (typical) | $0 | $300-$1,000 | +$300 to +$1,000 |
| Venting (new wall penetration + concentric pipe) | $0-$200 (B-vent inspect) | $400-$900 | +$400 to +$900 |
| Old tank removal + disposal | $50-$150 (in price) | $150-$300 | +$100 to +$150 |
| Electrical (120V for ignition) | $0 | $0-$300 | +$0 to +$300 |
| Permit + inspection | $25-$300 | $50-$400 | +$25 to +$100 |
| Total range | $1,000-$2,500 | $3,500-$6,500 | +$2,000 to +$4,000 |
The payback math, honestly
A gas tankless saves about 22 to 27 percent per year on hot water energy versus a standard gas tank, per DOE Energy Saver guidance. For a family of four on standard gas rates that translates to $60 to $130 per year saved. Annual maintenance on a tankless (descaling, screen-clean) runs $100 to $200 every 2 to 3 years, partly offsetting the savings. Net annual benefit: roughly $40 to $90 per year. Recovering a $2,500 conversion premium at $90 per year is a 28 year payback. At $40 per year, it never breaks even within the unit's 18 to 22 year life.
This is why the case for tankless conversion is usually not pure economics. The honest reasons people convert: they have run out of hot water repeatedly on the existing tank and want true endless flow; they want to free up the closet or basement footprint that the tank occupies; they are remodelling adjacent space and the existing vent or location no longer fits; they are planning to stay in the home long enough that comfort and reliability matter more than payback math. All valid. None of them are "the savings will pay for the install".
If you are weighing the conversion purely on operating-cost grounds, a heat pump water heater is the better answer for most households. The annual saving over a gas tank is $50 to $150 lower, similar to tankless, but the IRA Section 25C 30 percent credit removes $600 to $1,000 of the install cost. See the HPWH page for the full comparison.
When the conversion is right at replacement
Three specific situations where converting at replacement is the right call even before considering payback. First, the existing tank location is in valuable space (a kitchen pantry, a basement bedroom area, a small closet near a primary bath) and freeing the footprint has real value. A wall-mounted tankless unit is roughly the size of a small suitcase and can move to a less-visible location, including the exterior wall in mild climates. Second, the family is genuinely running out of hot water on the existing 50 or 75 gallon tank and the alternative is upsizing to 80 gallon (which costs $300 to $700 more anyway and still does not deliver endless flow). Third, the existing chimney has been demolished or condemned and the venting work for any gas tank replacement is non-trivial; the marginal cost of going to tankless and its dedicated concentric vent shrinks.
Conversely, the conversion is the wrong call when: the gas line run from the meter to the appliance is over 50 feet and would require deep wall work to resize; the household is moving within 5 years (the next buyer rarely pays a premium for tankless); the basement is unheated and pipes have ever frozen (tankless freeze-protection is harder than tank); or there is no exterior wall within 10 feet for venting. For sister-site detail on the tankless install side specifically, see the tankless conversion methodology.
Top tankless brands for conversion in 2026
The conversion market is dominated by four brands, each with different installer networks and warranty terms. Rinnai (RU and RX series) is the highest-volume residential brand with the widest installer network. Navien (NPE and NPN series) is the leader in condensing-tankless with high UEF. Noritz (NRC and NCC series) is competitive on price with a strong commercial heritage. Rheem (RTGH series) is the Home Depot mainstream option with broad parts availability and is most likely to be in stock at a local distributor on a same-day basis.
Unit cost for a mid-flow 9 GPM model runs $1,200 to $2,000 across brands at April 2026 retail; the conversion premium is driven more by labour and ancillary work than by unit choice. Warranty terms cluster at 12 years on the heat exchanger and 5 years on parts, with brand-specific installer-network warranty extensions (Rinnai Smart-Sensor Pros, Navien IPP) adding 2 to 3 years of labour coverage at a $150 to $300 install-cost premium. Detail on these certifications lives on the tankless installer methodology site.