How much does it cost to replace an 80-gallon water heater?

Q: How much does it cost to replace an 80-gallon water heater?

Replacing an 80-gallon tank water heater costs $1,000 to $4,000 installed. This Old House (June 2026) puts it at $1,000 to $3,000; Fixr (January 2026) puts it at $1,200 to $3,600 for all fuels and $1,300 to $4,000 for gas. Two costs are specific to this size: floor reinforcement at $300 to $800, and the fact that 80 gallons is the standard size for heat pump tanks, which changes the whole calculation.

The published ranges

Source	80-gallon tank, installed	Date
This Old House	$1,000 to $3,000	June 2026
Fixr, all fuel types	$1,200 to $3,600	January 2026
Fixr, gas units only	$1,300 to $4,000	January 2026

Neither source publishes a dedicated 80-gallon guide, so these come from their size tables rather than from a page built around this size. Both agree on the shape: 80 gallons is the most expensive common tank size, roughly twice the bottom of a 40-gallon job.

What is specific to this size

Weight. This Old House prices floor reinforcement for 80-gallon units at $300 to $800 where the structure needs it, and notes the same job for 40-gallon tanks at $100 to $200 for basic bracing. An 80-gallon tank holds about 667 pounds of water alone, before the weight of the tank itself (our arithmetic, at 8.34 pounds per US gallon; neither source states the figure). On a slab this is a non-issue. On a wood-framed floor, in an attic, or above finished space, it is a question worth asking before the quote is signed.

It is the heat pump size. Heat pump water heaters are overwhelmingly sold in 50-, 65- and 80-gallon electric tanks. If you are replacing an 80-gallon electric unit, a hybrid is a direct swap in both size and fuel, and the running cost difference at this capacity is the largest of any size. See heat pump water heater cost.

Attic and closet installs cost more here. This Old House prices attic installations at $200 to $1,000 extra for access and safety measures, and utility closet retrofits at $200 to $800 for ventilation improvements. An 80-gallon tank is the size most likely to make a tight location genuinely difficult.

Where the money goes

Line item	Range	Source
Labor, tank swap	$300 to $1,500 (18% to 50% of the total)	Fixr
Labor, gas tank, 20% to 25% of the total	$200 to $650	Fixr
Plumber hourly rate, 1 to 3 hour job	$40 to $200	This Old House
Floor reinforcement	$300 to $800	This Old House
Attic installation surcharge	$200 to $1,000	This Old House
Old tank removal and disposal	$100 to $300	This Old House
Old tank removal and disposal	$100 to $500	Fixr
Permit and inspection	$50 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
Expansion tank	$40 to $150	This Old House
Water line relocation or new shutoffs	$200 to $600	This Old House

Do you actually need 80 gallons?

Fixr puts 80 gallons at six or more people; This Old House says families of five or more need at least 75. Both are headcount rules, and headcount is a poor proxy for peak demand.

Our assumption, stated as such: the households that genuinely need 80 gallons are usually the ones with simultaneous demand, not just many people. Three bathrooms running at once, or a large soaking tub, will empty a 50-gallon tank regardless of how many people live there. Fixr makes the same point for the 50-gallon size, naming large soaking tubs, multiple high-flow showerheads and simultaneous appliance use as the reasons to go bigger. Neither source frames it this way, so treat this as our reading.

If the problem is a single high-draw fixture rather than sustained demand, a higher first-hour rating on a smaller tank can be the cheaper fix than jumping to 80 gallons. Ask the contractor for the first-hour rating of what they are quoting, not just the gallons.

Running cost at this size

Neither source publishes annual operating costs for an 80-gallon tank specifically. The closest published figures are Fixr's for a 75-gallon tank: $700 to $1,100 a year for electric, $400 to $600 for gas, $200 to $400 for a hybrid heat pump. An 80-gallon tank will sit at or slightly above the top of those ranges. We are not inventing an 80-gallon number that no source publishes.

That gap is the real argument at this size. An electric 80-gallon tank can cost more to run over ten years than it cost to buy and install.

How to read a quote for this job

Three questions a good quote answers at this size: what the first-hour rating is, whether the floor and the location were assessed, and what the vent needs on a gas unit. If you are replacing an electric tank, ask for a hybrid quote alongside the standard one. It is the only size where the two are a genuine like-for-like comparison.

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.