What's Involved
Tankless Water Heater Installation Requirements
Installation is more involved than a standard tank replacement. Understanding the requirements upfront prevents budget surprises and ensures a safe, code-compliant installation.
Professional Installation Required
DIY installation is not recommended and may void your warranty. Gas units involve combustion and venting hazards. Electric units require high-amperage wiring. Both require permits and inspections in most jurisdictions.
Gas Tankless Requirements
| Requirement | Cost | Notes |
|---|---|---|
| Gas line sizing/upgrade | $200–$800 | 3/4" minimum for most units |
| Stainless steel venting | $300–$1,000 | Category III or IV vent pipe |
| Condensate drain | $100–$300 | Required for condensing units |
| Electrical outlet (120V) | $100–$250 | For electronic ignition & controls |
| Water line connections | $100–$300 | 3/4" copper or PEX |
| Mounting bracket | $50–$150 | Wall-mount on exterior or interior |
| Permits & inspection | $50–$300 | Required in most jurisdictions |
Electric Tankless Requirements
| Requirement | Cost | Notes |
|---|---|---|
| Electrical panel upgrade | $300–$2,000 | May need 200A panel |
| Dedicated circuit(s) | $200–$600 | 2–3 circuits of 40–60 amps each |
| Heavy-gauge wiring (6–8 AWG) | $150–$400 | From panel to unit |
| Water line connections | $100–$300 | 3/4" copper or PEX |
| Mounting hardware | $25–$75 | Compact wall-mount |
| Permits & inspection | $50–$300 | Electrical permit required |
Venting Requirements for Gas Units
Gas tankless water heaters produce exhaust gases that must be properly vented to the outside. There are two main venting configurations:
- Direct vent (sealed combustion): Uses a concentric vent pipe that draws outside air for combustion and exhausts through the same wall penetration. Safest option for indoor installation. Costs $300–$600.
- Power vent: Uses an internal fan to push exhaust through PVC or stainless steel vent pipe. Allows longer vent runs but requires electrical connection. Costs $400–$1,000 depending on length.
Never use existing B-vent (double-wall aluminum) from a standard tank heater — tankless exhaust temperatures require Category III or IV stainless steel vent pipe.
Electrical Panel Considerations
Electric tankless units draw significant amperage. A whole-house electric model typically requires 120–150 amps of dedicated capacity across 2–3 circuits. If your home has a 100-amp or 150-amp panel, you'll likely need an upgrade to 200 amps ($1,000–$2,000).
Even some 200-amp panels may not have enough spare capacity. Have an electrician evaluate your panel's current load before choosing an electric tankless unit.
Permits and Inspections
Most jurisdictions require permits for water heater installation. Gas installations typically need both plumbing and gas permits. Electric installations require an electrical permit. Expect $50–$300 in permit fees plus an inspection visit. Your installer should handle the permit process.