Cost to Install a Tankless Waterheater

What would the cost be to replace an existing water heater with a tankless water heater to include plumbing.

Installation of a tankless (on-demand) water heater can sometimes require an upgrade of the natural gas pipe. The high demand of the tankless heater when working at full water flow demands that you pay attention to the manufacturers requirements.

In this installation the 3/4″ gas line was feeding both the furnace and the water heater. Although several plumbers stated that the new water heater would work, I was skeptical. The manufacturer recommended 1 1/4″ line given the installation location relative to the gas main and the amount of load on the line. The plumber easily installed a flex gas line.

The second consideration is the inclusion of discharge valves for flushing of the system. In hard water/high mineral content water systems this is particularly important.

If you are a contractor or a handyman, how much would this job cost in your area?

Low Price including appliance and materials: $1600

Consensus Price including appliance and materials: $2200

High Price including appliance and materials: $3500

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What would a fair price be?