Installing a tankless water heater offers on‑demand hot water, space savings, and improved energy efficiency for many homes. This guide covers sizing, installation steps, venting, gas versus electric options, costs, and maintenance to help homeowners plan a successful tankless water heater installation in the United States.

Sizing And Performance

Correct sizing ensures a reliable supply of hot water and optimal energy use. Tankless units are rated by temperature rise and gallons per minute (GPM). A typical family might need 2–3 fixtures at once, while larger households require higher‑flow models. When selecting a unit, consider peak demand, incoming water temperature in your climate, and desired first‑hour rating. Key considerations include:

Determine simultaneous hot water usage (showers, sinks, laundry, dishwasher).
Estimate needed GPM at your climate’s coldest month.
Account for incoming water temperature; in colder regions, more GPM may be required for the same demand.
Plan for future needs, such as a bathroom remodel or added fixtures.

Installation Process

Installing a tankless water heater involves water and gas or electrical connections, venting (for gas), and proper clearance. While some skilled DIYers pursue simple electric tankless installs, most gas and all complex installations should be performed by a licensed professional to meet code requirements and safety standards. Typical steps include:

Shut off water, gas, and electrical supplies; drain the existing system.
Mount the unit on a sturdy wall with adequate clearance and ventilation for gas models.
Connect cold and hot water lines, plus a condensate drain when applicable.
Install gas supply lines with proper pressure regulation and a dedicated vent (for gas models).
Wire the unit to a suitable electrical circuit, including a suitable breaker and, if required, a dedicated line and GFCI protection for certain models.
Commission and test for leaks, proper venting, and correct temperatures.

Vent And Combustion Considerations

Gas‑fired tankless water heaters require proper venting and combustion air. In the U.S., venting materials and clearances are dictated by local codes and the manufacturer’s instructions. Common options include concentric, dual‑flue, or dedicated exhaust pipes. Important points:

Vent material must be rated for direct‑vent or power‑vent applications, typically stainless steel or aluminum depending on model and heat output.
Proper vent sizing prevents backdrafts and ensures safe exhaust of combustion gases.
Combustion air may be drawn from outside or from a dedicated interior space, depending on installation and code requirements.
Existing chase or venting routes may need modification to accommodate the unit’s vent diameter and length.

Gas Versus Electric Tankless Models

Choosing between gas and electric tankless water heaters depends on climate, water usage, and electrical/venting infrastructure.

Gas tankless: Typically provides higher flow and is well-suited for larger households or colder climates. Requires proper venting, venting clearances, and a gas line that meets pressure requirements.
Electric tankless: Easier to install in some renovations, no venting needed, but higher electrical load. May require multiple high‑amperage circuits or a dedicated service panel, particularly in larger homes.
Oil or propane variants exist but are less common in typical U.S. residential installs.

Cost To Install And Savings

Costs vary by type, capacity, and regional labor rates. A ballpark range for a tankless water heater installation is:

Electric models: $800–$2,500 for unit and installation, depending on amperage and wiring needs.
Gas models: $1,000–$3,500 or more, including venting and gas line work.
Additional expenses may include permits, insulation, and minor plumbing or cabinetry adjustments.

Long‑term savings come from reduced standby heat loss and potentially lower energy bills, especially with higher‑efficiency models. In colder climates, a properly sized unit can still deliver hot water efficiently, but undersizing can lead to frequent cold water bursts during peak usage.

Maintenance And Longevity

Regular maintenance helps sustain performance and extend life. Common maintenance tasks include:

Descaling and flushing to remove mineral buildup, especially in hard water areas.
Inspecting and replacing anode rods or protective liners if the model requires them.
Seasonal checks of venting, condensate drains, and electrical connections.
Flushing the system with a manufacturer‑recommended solution to preserve heat exchanger efficiency.

Most tankless units have longer lifespans than traditional tanks, often 15–20 years with proper care.

Cold Climate And Recirculation Considerations

In colder regions, tankless water heaters may take longer to deliver hot water to distant fixtures, unless a recirculation loop or buffer tank is installed. Options include:

Point‑of‑use mini‑globe heaters near distant fixtures.
Whole‑house recirculation loops with a pump and timer to minimize wait times.
Hybrid systems combining a small storage tank with tankless units to balance speed and efficiency.

Safety, Codes, And Warranties

Code compliance and safety are crucial in any installation. Homeowners should:

Obtain local permits and have inspections to verify venting, gas lines, electrical work, and plumbing connections.
Follow manufacturer installation manuals for each model’s clearances and connection requirements.
Review warranty terms, including coverage for improper installation or venting deficiencies.

DIY Versus Hiring A Pro

While some electric tankless installations are feasible for skilled DIYers, most installations—especially gas models—benefit from a licensed professional. Pros ensure:

Proper sizing and performance verification with test runs.
Code compliance and safe venting routes.
Correct electrical or gas connections and leak testing.
Warranty protection by adhering to installation guidelines.

Frequently Asked Questions

How do you determine the right size tankless water heater? Consider peak demand, climate, and incoming water temperature; use manufacturer sizing charts and consult a professional if in doubt.
Is a tankless water heater worth it for a small apartment? Yes, especially electric models, where space savings and efficiency can offset costs; ensure electrical requirements are met.
Will installing a tankless water heater increase home resale value? Often yes, as buyers value energy efficiency and reliability of hot water supply.