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3-Bath Tankless Water Heater Cost: Unit & Install

How much is a tankless water heater for a 3-bathroom house?

For a typical 3-bathroom house, a tankless water heater often costs about $1,200–$3,500 for the unit, and roughly $2,500–$6,500 installed. The wide range comes down to fuel type (gas vs. electric), the flow rate (GPM) you need for simultaneous showers, and whether your home needs gas-line, venting, or electrical upgrades.

Typical price ranges (unit only)

Gas tankless: about $1,100–$2,800 for most mid-to-high capacity models. Condensing units and higher BTU ratings trend toward the upper end.

Electric tankless: about $400–$1,500, but whole-home electric models sized for multiple bathrooms can require major electrical capacity, which can increase total project cost.

Installed cost for a 3-bath setup

Like-for-like replacement (gas to gas): commonly $2,500–$4,500 installed when existing venting, gas supply, and location work well.

Upgrades required: $4,500–$6,500+ installed if you need a larger gas line, new venting, condensate drain (for condensing models), relocation, or permit-intensive modifications.

Why three bathrooms can push the price up

Three bathrooms often means the heater must support overlapping hot-water draws, such as a shower plus a second shower or dishwasher. That typically requires a higher GPM rating and higher BTU input on gas models, which increases equipment cost and can trigger installation upgrades. To understand how flow rate and BTU sizing affect both comfort and price, use this sizing guide: indoor tankless gas water heater sizing (GPM & BTU).

Budgeting tips before you buy

Confirm your incoming water temperature, count likely simultaneous uses, and ask an installer whether your gas meter and line diameter can support the needed BTUs. Also factor in ongoing maintenance (like descaling) and whether adding a small recirculation setup is worth it for faster hot water at distant bathrooms.

FAQ

What size tankless water heater do I need for a 3-bathroom house?

Many 3-bathroom homes land around 7–10 GPM depending on simultaneous use and local groundwater temperature. A pro can match that demand to the right BTU range and confirm your gas line and venting can support it.