Repair cost by water heater type
| Type | Repair cost | Source |
|---|---|---|
| Tankless, electric | $100 to $600 | Fixr |
| Tankless, gas | $150 to $650 | Fixr |
| Tankless, overall | $100 to $650 | Fixr |
| Tank, electric | $150 to $650 | Fixr |
| Tank, gas | $175 to $750 | Fixr |
| Hybrid heat pump | $150 to $900 | Fixr |
| Solar | $150 to $900 | Fixr |
Tankless is the cheapest type to repair, and Fixr explains why: there is no tank, so there is no risk of cracks or tank problems, and all of the components are usually very easy to access. Tank repair alone runs $250 to $1,000 on a conventional unit, and tank replacement $600 to $2,000. None of that exists on a tankless heater.
Set against it, at the other end, is the hybrid heat pump at $150 to $900: a tank plus a heat pump, coils and a compressor, so more parts to go wrong. See heat pump water heater cost.
The cost that actually recurs
Repairs are occasional. Descaling is annual, and it is the number that belongs in a tankless budget.
| Maintenance job | Cost | Source |
|---|---|---|
| Annual descaling | $100 to $500 | This Old House |
| Annual system cleaning | $100 to $200 | This Old House |
A tankless unit heats water by passing it through a heat exchanger at high temperature. In hard water, minerals deposit on the exchanger surface. Fixr is direct about the consequence: tankless heaters do not work as well with hard water, and if the unit is not serviced regularly it cannot work as efficiently or last nearly as long.
That last clause is the whole argument. The published lifespan of 15 to 20 years, which is most of the case for buying tankless in the first place, assumes the descaling is being done.
Our arithmetic, stated as such: at $100 to $500 a year over 20 years, descaling costs $2,000 to $10,000, which exceeds the $1,200 to $3,500 the unit cost to install. Neither source adds it up this way. The honest reading is that the low end of that range, which This Old House also gives as $100 to $200 for an annual cleaning, is the realistic figure for most homes, and the $500 top end is for hard water and a large unit.
This Old House also notes a homeowner on its own team does the annual flush himself, spending an hour flushing the unit with vinegar.
What goes wrong on a tankless unit
Fixr's repair figures do not break down by component for tankless units the way they do for tanks, so we are not going to list part prices that are not published. What the sources do name:
Scale on the heat exchanger. The dominant failure path, addressed by descaling rather than repair.
Ignition and controls. Fixr notes a tankless unit does not work at all in a power outage, including gas models, because the controls and ignition need electricity. That is a design characteristic, not a fault, but it is the most common reason people think the unit has failed.
Undersized supply. If the unit was installed without upgrading the gas line or the electrical service, it will underperform in ways that read as a fault. This Old House puts the electric requirement at 120 to 160 amps dedicated plus multiple 240-volt circuits, and the gas line upsize at $350 to $800. That is an installation problem, not a repair. See tank to tankless conversion cost.
The 3 to 5 second delay before hot water reaches the tap is normal on a tankless unit (This Old House), not a fault to be repaired.
Repair or replace, for a tankless unit
The published rules are the same as for a tank, and they land differently because the numbers are different.
Fixr's rule: repair if the unit has at least half its expected lifespan remaining and the repair costs under 50% of replacement. This Old House's: replace when repair exceeds half the replacement cost, or the unit is 10 or more years old.
Against a tankless replacement at $1,200 to $3,500 (This Old House) or $2,500 to $4,500 (Fixr), the 50% threshold is roughly $600 to $1,750. Every repair figure in the table at the top of this page falls below it. On a tankless unit, the repair is almost always the right call on cost alone.
The age half of the rule is where it turns. This Old House's flat 10-year test does not transfer well to an appliance both sources expect to last 15 to 20 years. Fixr's proportional rule is the better fit here: half of 15 to 20 years is 8 to 10, so a 12-year-old tankless unit with a $500 fault is still worth repairing on Fixr's test and not on This Old House's.
Our reading, stated as such: use the proportional rule for tankless. The flat 10-year figure was written for tanks, where it matches the 8-to-12-year life. Neither source says which rule applies to which type.
Related: repair or replace, tank to tankless conversion cost, maintenance cost.
Sources
- Fixr, Water Heater Repair Cost, updated August 29, 2025
- This Old House, How Much Does Tankless Water Heater Installation Cost?, updated June 12, 2026
- Fixr, Tankless Water Heater Installation Cost, updated January 31, 2025
Price figures are national US ranges from the sources above as of the date shown. Your local price depends on labor rates, permits and site conditions. Read how we get our numbers.