How much does it cost to replace a 40-gallon water heater?

Q: How much does it cost to replace a 40-gallon water heater?

Replacing a 40-gallon tank water heater costs $600 to $2,300 installed. Fixr (January 2026) puts it at $700 to $2,300 with an average of $1,650; This Old House (June 2026) puts it at $600 to $1,200. The gap is not a disagreement about the same job: the low figure is a bare like-for-like electric swap, the high figure includes gas venting, code items and premium units.

Three published ranges, and why they differ

Source	40-gallon tank, installed	Date
Fixr, dedicated 40-gallon guide	$700 to $2,300, average $1,650	January 2026
Fixr, general size table	$550 to $2,300	January 2026
This Old House	$600 to $1,200	June 2026

Fixr publishes two different low ends for the same tank size in two different guides updated the same month. Its dedicated 40-gallon page says $700, its general size table says $550. We have no basis to pick between them, so we report both.

The bigger gap is This Old House's $1,200 ceiling against Fixr's $2,300. These are not the same job. This Old House builds its figure from Home Depot equipment prices plus a basic install: a $600 to $1,000 unit and $300 to $800 of labor. Fixr's ceiling includes gas venting work, permits at the top of the range, code upgrades and premium long-warranty units. If your job is an electric-for-electric swap in an accessible basement, the This Old House range is the one to plan against. If you are replacing a gas unit and the vent or the code items are in play, plan against Fixr's.

By fuel type

Type	Installed cost	Source
Electric	$700 to $1,650	Fixr
Gas or propane	$700 to $2,300	Fixr
Hybrid heat pump	$1,600 to $5,000	Fixr
Solar	$2,000 to $7,000+	Fixr

Where the money goes

Line item	Range	Source
Labor, 20% to 50% of the total	$140 to $1,150	Fixr
Plumber hourly rate, 2 to 4 hour job	$45 to $200	Fixr
Unit only, from retail pricing	$600 to $1,000	This Old House
Old tank haul-away	$50 to $150	Fixr
Old tank haul-away	$100 to $300	This Old House
Expansion tank	$150 to $400	Fixr
Expansion tank	$40 to $150	This Old House
Permit and inspection	$50 to $200	This Old House
Floor bracing for the added weight	$100 to $200	This Old House
Basic gas venting	$300 to $500	This Old House
Power vent plus its electrical work	$600 to $1,100	This Old House

One figure we are not repeating. Fixr's 40-gallon page prices a direct-vent or power-vent system at $3,400 to $10,200. That is five to ten times every other published venting figure we found, including This Old House's $300 to $1,000 for the same work in June 2026. We treat it as a data error on that page and use the This Old House figures above. This is our judgement, not something either source states.

Annual running cost

Fuel	Per year	Source
Electric	$550 to $700	Fixr
Gas	$300 to $450	Fixr
Hybrid heat pump	$200 to $300	Fixr
Solar	$100 to $200	Fixr

Over a 10-year life, the gap between electric and gas running costs is roughly $2,000 to $2,500. That is larger than the entire purchase price difference between the two, which is the reason the fuel question matters more than the sticker price.

Is 40 gallons the right size?

Fixr puts a 40-gallon tank at one to four people and says a family of four with typical use is usually fine. This Old House is more conservative: two to three people at 40 to 50 gallons, three to four people at 50 to 60. The honest answer is that it depends on simultaneous use, not headcount. A 40-gallon tank gives roughly 40 to 50 minutes of continuous showering at a standard flow rate (Fixr), because the tank output mixes with cold water.

If you run two showers back to back and the second one goes cold, the fix is a 50-gallon tank or a higher-recovery unit, not a bigger 40.

How to read a quote for this job

A complete quote names the unit brand, model and warranty length, lists labor separately, and says whether the permit, the haul-away and any expansion tank are included. Ask specifically about venting on a gas unit: it is the single line item where published estimates vary most, and it is the one a same-day quote is most likely to leave out.

Use the replacement cost calculator to build your own range from these line items.

Sources

Price figures are national US ranges from the sources above as of the date shown. Your local price depends on labor rates, permits and site conditions. Read how we get our numbers.