The national price ranges
National guides list $600 to $3,000 to replace a 40 gallon tank heater. They give $600 to $3,100 for a new 40 to 50 gallon tank installed. Tankless units come in at about $1,400 to $5,600 installed. Most homes land in the middle of those ranges, with the extremes tied to unusual layouts or high-end equipment.
| Type | Installed range | What pushes it higher |
|---|---|---|
| Tank, 40 to 50 gallon | $600 to $3,100 | Power vent, tight access, code upgrades |
| Tank, replacement of a 40 gallon | $600 to $3,000 | Moving the unit, new shutoff valves |
| Tankless | $1,400 to $5,600 | Larger gas line, new venting, condensate drain |
If one quote is far below the others, ask what it leaves out. A very low number often skips the expansion tank, the permit or the removal of the old unit.
Line items that change the total
A water heater quote has a base price for the unit and labor, then add-ons that depend on what the install requires. National guides list these typical ranges.
These figures come from national cost guides and are not a local quote. We give a clear price before work starts.
Before the installer arrives
- Locate the main water shutoff and the gas shutoff, and show them to the installer.
- Clear a path to the heater and keep pets and children out of the work area.
- Do not relight a pilot or touch gas fittings yourself if the old unit was leaking.
- If you smell gas, leave the house and call Spire at 800-887-4173 or 911 before anyone else.
Hazelwood factors that touch the price
Plumbing permits and inspections in Hazelwood run through St. Louis County, so ask any installer who pulls the permit and whether it is on the invoice. A quote with no permit line may mean the permit is skipped, which can cause trouble at resale or on an insurance claim.
Missouri American Water reported total hardness at its Missouri River plants of roughly 5 to 13 grains per gallon in 2023, which is moderately hard to very hard. Hard water builds sediment at the bottom of a tank and cuts efficiency, so test your tap or call the utility at 866-430-0820. A tankless unit in hard water often needs periodic descaling, so factor that in before choosing.
The utility also disinfects with chloramines. That can age rubber seals and fill valve parts faster, so ask your installer to use fittings and connectors rated for it.
The national prices in this guide assume gas units built to ANSI Z21.10.1 or electric storage units listed to UL 174. A cheaper bid that skips the relief valve, the discharge pipe or the permit is not comparable, so match the scope line by line.
Tank or tankless on the price tag
A tank heater costs less up front and is simpler to service. A tankless unit costs more to install but can last longer and takes less floor space. The extra bill usually comes from the gas line and venting work, not the unit itself.
If your gas line is too small, the upgrade can add $350 to $2,000. If you are switching from electric to gas, you may need new venting and a gas line on top of the unit. Our page on tankless water heaters explains when the extra cost pays off and when it does not.
How to compare two quotes
- Match the size and fuel. A 40 gallon gas quote and a 50 gallon electric quote are different jobs. Compare like with like.
- Ask what is included. Check for the permit, expansion tank, new flex lines, shutoff valves and haul-away.
- Ask about venting. Find out whether the existing flue gets reused and whether it passes a check, since a bad flue is a safety issue.
- Ask about the warranty. The tank warranty comes from the manufacturer, and labor coverage depends on the installer.
- Ask for the price in writing. A plumber should state the total before work starts.
When replacement is smarter than repair
Repair is the better call for a failed thermostat, a bad heating element or a leaking relief valve. Replacement makes sense when the tank itself leaks, when the heater is past its expected life, or when repairs keep stacking up. A leak from the tank body cannot be fixed.
Our water heater repair service looks at the failed part first and tells you if a fix is realistic. When replacement is the answer, water heater installation covers the new unit, venting and connections. Homeowners in Maryland Heights and Black Jack often ask the same cost questions.
If the heater is leaking now, shut off the cold water valve above it, turn off the gas or power, and call the 24/7 line. Gas smell means leave the house and call Spire at 800-887-4173 or 911.
Frequently asked questions
National guides list roughly $600 to $3,100 for a 40 to 50 gallon tank heater and $1,400 to $5,600 for a tankless unit. Your price depends on the fuel, access, venting and permit.
It may leave out the permit, expansion tank, venting or haul-away. Ask for every line item so you can compare the full scope.
Plumbing permits and inspections in Hazelwood are handled by St. Louis County through the city. Ask your plumber to confirm and pull it. Inspections and Permits can be reached at 314-513-5034.
It can. Missouri American Water reported hardness at its Missouri River plants of about 5 to 13 grains per gallon in 2023, and sediment builds up faster in hard water. Flushing the tank each year helps.
Not always, but it is common on closed systems with a check valve or pressure reducing valve. Your plumber can tell you whether yours needs one.
Leave the house and call Spire's emergency line at 800-887-4173 or 911 from outside. Do not turn lights or appliances on or off on your way out.
Questions about your situation? A licensed plumber is on the line any hour.
Call (855) 575-2890