Tank vs. Tankless Water Heater: Real Cost Comparison (2026)
A gas tankless water heater costs about twice as much to install as a tank, and its energy savings alone won't pay that back. Its longer life might. Here's the full 20-year math, plus when a heat pump beats both.
If your water heater just died, or a plumber told you it's on its way out, you've probably been handed two quotes: one to swap in a new tank, and one for a tankless system that costs a lot more. Which one is actually cheaper?
The short answer: a gas tankless unit costs roughly twice as much to install, and its energy savings alone don't pay that back. What can tip the math is lifespan. A tankless unit is rated to last about twice as long as a tank, so over 20 years you'd likely buy one tankless unit or two tanks.
Here's the full comparison, with every number sourced.
Is Your Current Water Heater Worth Repairing?
Before you compare replacements, check whether a repair makes more sense. Enter your unit's age and repair quote for an instant recommendation.
Repair or Replace? →Installed Cost: Tank vs. Tankless
BuildCost's national installed prices for a replacement, including labor, are:
| System | Installed cost range | Typical |
|---|---|---|
| Standard tank (electric) | $1,200–$2,400 | ~$1,800 |
| Standard tank (gas) | $1,450–$3,050 | ~$2,250 |
| Tankless (electric) | $2,200–$4,150 | ~$3,200 |
| Tankless (gas) | $3,100–$5,450 | ~$4,300 |
Our tankless figures include the extra work a tank-to-tankless conversion usually needs. Other published averages run lower: HomeAdvisor (updated June 2026) puts the average tankless install at $2,641 (typically $1,406–$3,902), and Fixr (January 2026) at $1,000–$4,000. The difference is usually the conversion work:
- Gas units often need new venting and a larger gas line. Fixr prices a power vent alone at $300–$1,000, and says converting to a wall-mounted tankless unit "will significantly increase labor costs."
- Electric whole-house units need at least 240V, 80-amp hard-wired service, and HomeAdvisor notes that some homes need 150-amp service overall to support one. A panel upgrade can turn a cheap unit into an expensive install.
- Permits run $25–$1,500 depending on your area, with the higher end when gas, electrical, or major plumbing work is involved (Fixr).
If you're replacing an existing tankless unit with another one, expect something closer to the HomeAdvisor and Fixr figures. If you're switching from a tank, get the conversion work itemized in the quote.
See water heater costs for your state →
Operating Cost: How Much Does Tankless Save?
Less than most people expect, at least for gas.
According to ENERGY STAR, a certified gas tankless water heater saves a family of four about $95 per year compared with a standard gas tank, or about $1,800 over its lifetime. The Department of Energy's consumer guidance puts tankless units at roughly 8% to 34% more efficient than storage tanks, with the larger savings in homes that use less hot water.
The reason is simple: a tank keeps 40 to 50 gallons hot around the clock, losing heat even when nobody's using it. A tankless unit only heats water while it's flowing.
Lifespan: Where Tankless Earns Its Keep
| System | Typical lifespan | Source |
|---|---|---|
| Tank (gas or electric) | 8–12 years | Rheem (HomeAdvisor cites 10–15) |
| Tankless | About 20 years | ENERGY STAR (Rheem cites 15–20+) |
That gap is what changes the math.
The 20-Year Math (Gas)
Here's a simple comparison for a gas home over 20 years, using today's prices:
| Gas tank | Gas tankless | |
|---|---|---|
| Units bought over 20 years | 2 (at ~10 years each) | 1 |
| Installed cost | 2 × $2,250 = $4,500 | $4,300 (conversion) |
| Energy savings vs. a tank | — | −$1,800 (ENERGY STAR) |
| Net 20-year cost | ~$4,500 | ~$2,500 |
On energy savings alone, tankless doesn't pay for itself. The ~$2,050 premium divided by $95 a year in savings works out to about 21 years, longer than the unit is rated to last. Tankless comes out ahead only if you count avoiding a second tank replacement.
That means the math depends on a few things:
- How long you'll stay. If you move in five years, you pay the full premium and the next owner gets most of the benefit.
- Whether the unit actually lasts. The 20-year figure assumes proper care. Tankless units need periodic descaling per the manufacturer's instructions, especially with hard water.
- Your real quotes. If your tankless install comes in closer to HomeAdvisor's $2,641 average, tankless wins by more. If it needs a panel upgrade or long gas line run, it wins by less, or not at all.
This is an illustration, not a forecast. It uses today's prices, ignores inflation and maintenance, and assumes a tank lasts 10 years. Plug in your own quotes.
Got Quotes? Check Them
See how a plumber's price for a new tank or tankless system compares with typical costs in your state.
Check My Quote →Have Electric? Look at a Heat Pump Water Heater
For homes without gas, the comparison that matters most isn't tank vs. tankless. It's a standard electric tank vs. a heat pump water heater, which moves heat from the surrounding air into the water instead of generating it.
According to ENERGY STAR, a certified heat pump water heater saves compared with a standard electric tank:
| Household size | Annual savings | Lifetime savings | Payback |
|---|---|---|---|
| 2 people | $270 | $2,050 | 5.5 years |
| 3 people | $410 | $3,830 | 3.7 years |
| 4 people | $550 | $5,610 | 2.7 years |
ENERGY STAR's assumptions: $0.146/kWh electricity, $1,503 extra upfront cost vs. a standard electric tank, and a 13-year lifespan.
That's a much faster payback than gas tankless. Heat pump units do need space and airflow around them and work best in a garage, basement, or utility room, so ask your installer whether your location fits.
Which Should You Choose?
A standard tank makes sense if:
- Your current tank failed and you need hot water back fast with a like-for-like swap.
- You expect to move within the next several years.
- Upfront cost matters more than long-term savings.
Gas tankless makes sense if:
- You plan to stay 15+ years.
- Your quote doesn't include a major gas line or venting overhaul, or you've priced that in.
- You want the space back. ENERGY STAR notes a tankless unit frees up "an extra closet's worth of space."
A heat pump water heater makes sense if:
- You have electric water heating today.
- You have a garage, basement, or utility space with room around the unit.
- You want the fastest payback of the three.
A Real Example
This post started with my own water heater. It stopped working, and when the plumber came out to repair it, he found it was more than 15 years old, and the part it needed cost over $1,000 and was a month away. Rather than wait weeks for a part for a unit well past its expected life, we asked him to quote replacements instead: three tank sizes and a tankless system.
That's the right move. A 15-year-old tank is past the 8–12 years Rheem cites, and a $1,000 repair is close to half the cost of a new tank, the point where Rheem says replacement is "almost always the better investment." Getting several replacement quotes at once, including tankless, makes it easy to run the 20-year math above with real numbers.
Run your own repair-or-replace check →
Frequently Asked Questions
Is a tankless water heater worth it? It depends mostly on how long you'll stay. For gas, ENERGY STAR estimates a certified tankless unit saves a family of four about $95 a year, which doesn't cover the extra installation cost within the unit's lifespan by itself. Because tankless units are rated to last about 20 years versus 8–12 for a tank, tankless can come out ahead over 20 years by avoiding a second tank replacement.
How much does it cost to switch from a tank to a tankless water heater? BuildCost's national estimate for a gas tankless conversion is $3,100–$5,450 installed, including the venting and gas line work conversions often need. HomeAdvisor's average for tankless installs overall is $2,641. Electric whole-house tankless units need at least 240V, 80-amp service, which can mean an electrical panel upgrade.
How long does a tankless water heater last? About 20 years, according to ENERGY STAR. Rheem cites 15–20+ years with proper care, including periodic descaling. Tank water heaters typically last 8–12 years (Rheem).
What's cheaper to run, tank or tankless? Tankless. ENERGY STAR estimates a certified gas tankless unit saves a family of four about $95 per year compared with a standard gas tank. For electric homes, a heat pump water heater saves far more: about $550 a year for a family of four, per ENERGY STAR.
Should I replace my water heater before it fails? If it's past its expected lifespan and needs a costly repair, replacing usually makes more sense than repairing. Use BuildCost's repair-or-replace tool to check your situation.
Sources
- HomeAdvisor: Tankless Water Heater Installation Cost (updated June 17, 2026)
- Fixr: Cost to Install a Water Heater (updated January 27, 2026)
- ENERGY STAR: Gas Tankless Water Heaters, Benefits & Savings (accessed October 14, 2026)
- ENERGY STAR: Heat Pump Water Heaters, Benefits & Savings (accessed October 14, 2026)
- Rheem: Water Heater Lifespan, When to Repair vs. Replace (accessed October 14, 2026)
- U.S. Department of Energy, Energy Saver consumer guidance on water heater efficiency (8%–34% efficiency range)
- Installed cost ranges by system type: BuildCost water heater cost data
Founder of BuildCost. Combines hands-on construction and trades experience with years of managing his own home renovation projects and a data and research background that drives how BuildCost aggregates and regionalizes cost data.
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