Gas Water Heater Replacement Cost

Gas Tank Water Heater Costs

A standard gas tank water heater includes three cost components: the unit itself, the installation labor, and any parts or code upgrades needed during installation.

The unit cost depends primarily on tank size and warranty length. A 40-gallon model with a 6-year warranty costs $400 to $700. A 50-gallon model with a 9-year warranty costs $600 to $1,200. Premium 50-gallon models with 12-year warranties and higher efficiency ratings run $1,000 to $1,800. The difference between warranty tiers from the same manufacturer typically comes down to thicker tank walls, a larger anode rod, and better insulation on the premium model.

Installation labor runs $300 to $700 for a standard gas tank replacement. A straightforward swap where the new unit matches the old one's venting type and gas line configuration takes two to three hours. The plumber disconnects the old unit, drains and removes it, positions the new unit, connects the water lines, connects the gas line, connects the vent, fills the tank, tests for gas leaks, lights the pilot (on models with a standing pilot), and verifies proper operation.

Venting Types and Costs

Atmospheric Vent (Natural Draft)

Atmospheric vent water heaters use the natural buoyancy of hot exhaust gases to draw combustion byproducts up through a metal flue pipe and out through the roof. This is the most common venting type in existing homes, and replacing one atmospheric vent unit with another is the simplest and cheapest installation. The vent pipe connects to an existing B-vent chimney, so no new venting is required unless the existing vent is damaged or undersized.

Atmospheric vent models are less efficient than power vent or direct vent models because they draw conditioned air from the surrounding space for combustion and lose some heat up the vent. They also require adequate combustion air supply in the space where they are installed, which may be an issue in tightly sealed homes or small mechanical closets.

Power Vent

Power vent water heaters use an electric fan to push exhaust gases through a PVC pipe that exits through a sidewall rather than the roof. This allows installation in spaces without access to a vertical vent chimney, such as interior closets or finished basements. Power vent models cost $200 to $500 more than atmospheric vent models, and the installation requires an electrical outlet near the water heater for the vent fan motor.

If you are converting from atmospheric vent to power vent, the plumber needs to run PVC vent pipe to an exterior wall and install a vent termination. This conversion adds $200 to $600 to the installation cost depending on the distance to the nearest exterior wall. However, a power vent unit may be the only option if your existing chimney has been sealed, shared with a furnace, or found to be in poor condition.

Direct Vent

Direct vent models use a sealed combustion system that draws outside air for combustion through a dedicated intake pipe and exhausts through a separate pipe, both running through an exterior wall. These units do not use indoor air for combustion, making them safe for tightly sealed spaces and small closets. Direct vent models cost $300 to $600 more than atmospheric vent models, and the installation requires proximity to an exterior wall for the double-pipe vent assembly.

Gas Line Requirements

The gas line supplying the water heater must deliver adequate volume at the correct pressure for the specific unit. Standard gas tank water heaters require a 1/2-inch gas line for most residential applications. If you are replacing a tank unit with a similar-size tank, the existing gas line is almost always adequate.

Converting from a tank to a gas tankless unit often requires a gas line upgrade. Tankless water heaters have higher BTU input ratings than tank models and typically need a 3/4-inch gas line, sometimes even 1-inch for larger units. If the existing gas line from the meter to the water heater location is 1/2-inch, the plumber must run a new, larger line. This upgrade costs $300 to $1,500 depending on the distance from the gas meter to the installation point and whether the line runs through finished walls or ceilings.

A gas sediment trap (also called a dirt leg or drip leg) is required by code at the gas connection to the water heater. This is a short vertical pipe below the gas shutoff valve that catches debris and moisture before they enter the burner assembly. Adding one during installation costs $15 to $50 in parts and is included in the standard installation labor.

Code Upgrades That Add Cost

When replacing a gas water heater, the plumber must bring the installation up to current code standards. Older installations may not have had certain safety requirements that are now mandatory. Common code upgrades include:

An expansion tank ($100 to $250 installed) is required on closed plumbing systems. A drain pan under the water heater ($30 to $75) is required in locations where a leak could cause property damage, particularly when the unit is above finished living space or on an upper floor. Seismic strapping ($15 to $75) is required in earthquake-prone areas including California. A temperature and pressure (T&P) relief valve discharge pipe must terminate within 6 inches of the floor or route to the exterior, which may require extending the existing pipe.

Natural Gas vs Propane

Natural gas and propane water heaters use the same basic technology, but the burner orifices are different sizes because the two fuels have different pressures and BTU content. Many models are available in both natural gas and propane versions, or the manufacturer sells a conversion kit ($20 to $50) to switch between fuels.

Propane costs more per BTU than natural gas in most markets, so annual operating costs for a propane water heater run $350 to $550 compared to $250 to $400 for natural gas. The unit costs are comparable. If your home is on propane, the installation is essentially the same as natural gas, though the plumber verifies that the propane regulator delivers the correct pressure for the water heater's requirements.

When to Consider Switching from Gas

If your current gas water heater is at the end of its lifespan, this is the natural time to evaluate whether a different fuel source makes sense. Switching from gas to a heat pump electric model eliminates the gas combustion, venting, and carbon monoxide concerns associated with gas units, and the federal tax credit of up to $2,000 can make the effective cost competitive with a gas replacement. However, the conversion requires running a dedicated 240-volt circuit to the water heater location, which adds $300 to $800 to the installation.

For most homeowners with an existing gas infrastructure that is in good condition, a gas-to-gas replacement remains the most cost-effective path. The gas line, venting, and connections are already in place, which keeps installation labor at its minimum.