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What you will actually pay a professional to install a tankless water heater, and which extras turn a $1,500 job into a $5,000 one.
Whether you are pricing a new tankless water heater install cost or a tankless water heater replacement cost, the cost to install tankless water heater units depends on the items below. Asking how much to install a tankless water heater without these details gives you a meaningless number.
| Item | Typical cost | When you need it |
|---|---|---|
| Installation labor | $600–$1,900 | Always |
| Removal and disposal of old tank | $100–$300 | Converting from a tank |
| Isolation (service) valve kit | $60–$200 | If not already installed |
| Gas line upsizing | $300–$1,500 | Gas units, when the existing line is too small |
| New venting (PVC or stainless) | $200–$900 | Indoor gas units |
| Condensate drain and neutralizer | $100–$300 | Condensing gas units |
| New 120V outlet | $150–$300 | Gas units without nearby power |
| Dedicated 240V circuits | $500–$1,500 | Whole-house electric |
| Electrical panel upgrade | $1,000–$3,000+ | When the panel can’t support the load |
| Permit | $25–$300 | Most jurisdictions |
| Relocating the heater | $500–$2,000 | Moving to a new wall or outside |
Figures are national estimates for 2026 drawn from published cost surveys and typical installer quotes; local prices can be higher in large metro areas.
A gas tankless water heater installation cost depends mostly on three things:
Electric tankless water heater installation cost is mostly electrical work. A 36 kW unit can draw about 150 amps and need several double-pole breakers and heavy-gauge copper wire. Homes with 200-amp service may have enough capacity; older 100-amp panels usually don’t. An electrician’s load calculation tells you before you buy. Small 120V or 240V point-of-use units are far cheaper to install.
Replacing a water heater with tankless is the most common job. Expect the conversion to add $150–$2,500 over a straight swap, depending on how much gas, venting and electrical work is needed. A full conversion often lands between $2,500 and $4,500 for gas.
So, how much is a tankless water heater installed in total? Combining the unit price and installation, the cost of tankless water heater and installation usually lands in the $2,500–$4,500 range for gas conversions. To replace tankless water heater cost is lower when the venting and gas line can be reused.
Our tankless water heater installation guide has a full checklist of questions to ask.
Buying your unit online and hiring a local licensed installer can lower total cost. Check that your installer agrees first.
Expect roughly $600–$1,900 in labor and $1,400–$4,500 total including the unit, materials and permit. Tank-to-tankless conversions that need a new gas line, venting or electrical service can cost more.
Replacing an existing tankless unit is usually the cheapest installation because gas, venting and valves are already in place. Labor is often $500–$1,000 plus the new unit, if the new model uses the same vent type.
The installation is simpler because there is no venting or gas line, but whole-house electric units often need new circuits and sometimes a panel upgrade, which can make them as expensive as gas.
Most U.S. cities and counties require a plumbing permit, and often a gas or electrical permit, for water heater installation. Permits commonly cost $25–$300. Your installer usually pulls it.
Electric point-of-use units are sometimes DIY-friendly for experienced homeowners where code allows. Gas and whole-house electric installs involve safety-critical work, often require a license and permit, and DIY installation can void the manufacturer’s warranty.
This guide is general information for U.S. homeowners, not professional advice. Gas, electrical and venting work must follow the manufacturer’s instructions and local codes, and in most areas requires a licensed plumber, electrician or gas fitter and a permit. Specifications and prices change; always confirm details on the product page and in the installation manual.
