Last updated: October 2026
A tank water heater usually costs about $600 to $2,700 installed, while a tankless water heater typically runs $1,400 to $3,900 for a like-for-like swap and $4,000 to $10,000 or more when converting from a tank requires a new gas line, venting or electrical upgrades. Tankless units use roughly 24% to 34% less energy in homes that use 41 gallons of hot water a day or less, and they last longer (20+ years versus 10 to 15), but the energy savings alone rarely pay back the higher upfront cost quickly. Choose tankless if you plan to stay in the home a long time, have gas service with adequate capacity, or need endless hot water; choose a tank if you want the lowest upfront cost, have hard water, or need a simple replacement.
Tankless vs tank at a glance
| Factor | Tank (storage) water heater | Tankless (on-demand) water heater |
|---|---|---|
| Typical installed cost (replacement) | $600 – $2,700 | $1,400 – $3,900 |
| Installed cost when converting from tank | N/A | Often $3,900 – $10,500 (gas line, venting, electrical) |
| Energy savings | Baseline | 24% – 34% for homes using ≤41 gal/day; 8% – 14% at ~86 gal/day (DOE) |
| Typical lifespan | 10 – 15 years | 20+ years |
| Hot water supply | Limited by tank size and recovery | Continuous, limited by flow rate (GPM) |
| Space | Floor footprint, roughly 16″–36″ diameter | Wall-mounted, about the size of a carry-on suitcase |
| Maintenance | Flush annually; check anode rod | Descale annually (more in hard water); clean inlet filter |
| Best for | Lower budgets, hard water, simple swaps, cold-climate electric homes | Long-term owners, gas homes, small spaces, high or irregular demand |
Not sure which one fits your home?
A licensed local plumber can check your gas line, venting and electrical panel and quote both options side by side, so you can compare real numbers instead of national averages.
Get free quotesHow each type works
A tank water heater stores 30 to 80 gallons of water and keeps it hot around the clock using a gas burner or electric elements. When you open a tap, hot water leaves the top of the tank and cold water refills the bottom. Because the stored water slowly loses heat through the tank walls (called standby loss), the heater cycles on even when no one is using water.
A tankless water heater heats water only when a tap opens. A flow sensor detects water moving through the unit (usually once flow reaches about 0.4 to 0.5 gallons per minute), fires the burner or electric elements, and heats the water as it passes through a heat exchanger. There’s no stored water, so there’s no standby loss. The trade-off is that the unit can only heat so many gallons per minute, and that number drops as your incoming water gets colder.
For a deeper look at fuel choice, see our guide to gas vs electric water heater replacement cost.
Upfront cost: tankless vs tank
The equipment price gap is smaller than most people expect. A 50-gallon gas or electric tank costs roughly $500 to $1,200 at retail, and whole-house tankless units run about $525 to $1,500 or more for mainstream gas models. The big difference is labor and the work around the unit.
| Cost item | Tank water heater | Tankless water heater |
|---|---|---|
| Unit (typical whole-house) | $500 – $1,200 (40–50 gal) | $525 – $1,500+ (gas); $400 – $900 (electric) |
| Labor, like-for-like replacement | $150 – $450 | $600 – $1,900 |
| Permit | $25 – $300 | $25 – $300, plus $50 – $300 for a gas permit where required |
| Haul-away of old unit | $100 – $500 (often included) | $100 – $500 (often included) |
| Typical total installed | $600 – $2,700 | $1,400 – $3,900 |
These ranges come from national cost guides (Angi, Bob Vila, Consumer Reports) and vary widely by region. For a full breakdown of tank pricing, read our water heater replacement cost guide or the 50-gallon water heater replacement cost page. For tankless-specific pricing, see tankless water heater cost.
Conversion cost: switching from a tank to tankless
Replacing an existing tankless unit with another tankless unit is straightforward. Converting from a tank is where budgets blow up, because a tankless heater demands much more fuel or power at once. A typical gas tank burner is rated around 40,000 BTU per hour; a whole-house gas tankless unit is commonly rated up to 199,000 BTU per hour. Electric tankless units commonly need 18 to 36 kW, which is far more than the single 30-amp circuit that feeds most electric tanks.
| Conversion item | Typical cost | When it’s needed |
|---|---|---|
| Gas line upsizing and meter sizing | $500 – $2,000 | Existing 1/2″ line can’t carry ~199,000 BTU, or meter is undersized |
| New venting and combustion air | $300 – $1,500 | Tankless units can’t share a standard tank flue; condensing units use PVC venting |
| Electrical panel and wiring (electric tankless) | $1,000 – $3,000 | Whole-house units often need 100–150 amps and a 200-amp service |
| Condensate drain and neutralizer | $200 – $500 | Condensing gas tankless units |
| Replumbing and relocation | $150 – $3,400 | Moving the unit to an exterior wall or new location |
| Drywall patching and access panels | $100 – $3,000 | Running new lines through finished walls |
| Typical conversion total (installed) | $3,900 – $10,500 | Same-fuel retrofit at the low end; electric-to-gas full conversion at the high end |
ConsumerAffairs puts a moderate same-fuel tank-to-tankless retrofit at about $3,900 to $6,000, an electric installation with electrical upgrades at $4,500 to $8,000, and a full fuel conversion at $6,000 to $10,500. Ask any installer to price the gas line, venting and electrical work as separate line items so you can see exactly where the money goes. Our water heater installation labor cost guide explains typical plumber rates.
Electric tankless: the panel problem
Electric tankless is cheap to buy but often expensive to wire. A popular 27 kW whole-house model (Rheem RETEX-27) requires three 40-amp double-pole breakers, which works out to roughly 112 amps at 240 volts. Many older homes with 100-amp or 150-amp service can’t add that load without a panel or service upgrade. Get an electrician to run a load calculation before you buy.
Operating cost and efficiency (UEF)
Water heater efficiency in the US is rated by Uniform Energy Factor (UEF), the federal test metric that replaced the old Energy Factor. Higher is better. You’ll find UEF on the spec sheet and EnergyGuide label, along with an estimated yearly energy cost.
| Type | Typical UEF range | Notes |
|---|---|---|
| Standard gas tank (atmospheric vent) | ~0.58 – 0.70 | Standby loss and flue losses keep efficiency lower |
| High-efficiency condensing gas tank | 0.80 – 0.90+ | ENERGY STAR gas storage models start around 0.81+ depending on size |
| Non-condensing gas tankless | ~0.80 – 0.87 | Uses stainless steel vent |
| Condensing gas tankless | ~0.92 – 0.97 | Secondary heat exchanger; PVC venting; needs condensate drain |
| Electric resistance tank | ~0.90 – 0.95 | Efficient at the element, but electricity costs more per BTU than gas in most areas |
| Electric tankless | ~0.98 – 0.99 | Little room to improve on an electric tank |
| Heat pump water heater (tank) | ~3.3 – 4.0+ | Moves heat instead of making it; by far the cheapest electric option to run |
The UEF ranges above are typical values from manufacturer spec sheets and ENERGY STAR criteria; check the exact model you’re quoted.
What the government and independent testing say
The US Department of Energy estimates that a tankless heater can be 24% to 34% more energy efficient than a conventional storage tank for homes using 41 gallons or less of hot water daily, and 8% to 14% more efficient for homes using around 86 gallons a day. In other words, the savings shrink as your household uses more hot water, because standby loss becomes a smaller share of total energy use.
Consumer Reports’ testing found similar real-world numbers. In its tests, gas tankless units cost about $195 a year to run versus about $245 for a gas tank, and electric tankless about $535 a year versus $580 for an electric tank. That’s a saving of roughly $45 to $50 a year at the energy prices CR used at the time. CR concluded that a gas tank-to-tankless swap could take around 22 to 27 years to pay back, while a heat pump water heater (about $240 a year to run in the same testing) paid back far faster for electric homes.
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Get free quotesPayback examples (illustrative)
The examples below are illustrative only. They use simple assumptions, not quotes or measured bills: 64 gallons of hot water a day heated by 67°F (similar to the federal test conditions), natural gas at $1.50 per therm and electricity at $0.17 per kWh. Your energy prices, usage and installation costs will differ.
| Scenario (illustrative) | Annual energy use | Annual cost | Annual savings vs baseline | Extra upfront cost | Simple payback |
|---|---|---|---|---|---|
| Gas tank, UEF 0.62 (baseline) | ~210 therms | ~$315 | — | — | — |
| Condensing gas tankless, UEF 0.93, simple swap | ~140 therms | ~$210 | ~$105 | ~$1,200 | ~11 years |
| Condensing gas tankless, UEF 0.93, with gas line + venting | ~140 therms | ~$210 | ~$105 | ~$3,000 | ~29 years |
| Electric tank, UEF 0.93 (baseline) | ~4,110 kWh | ~$700 | — | — | — |
| Electric tankless, UEF 0.99, with panel upgrade | ~3,860 kWh | ~$655 | ~$40 | ~$2,500 | 50+ years |
| Heat pump water heater, UEF 3.5 | ~1,090 kWh | ~$185 | ~$515 | ~$1,500 | ~3 years |
Two lessons stand out. First, a gas tankless upgrade can pay back within its lifespan if the install is simple, but conversion work can push payback past the life of the unit. Second, electric tankless saves very little over an electric tank because both already convert nearly all the electricity to heat. If you’re on electricity and want lower bills, a heat pump water heater usually beats tankless by a wide margin. (The federal 25C tax credit that covered heat pump and some gas water heaters ended for equipment installed after December 31, 2025, but many utilities and states still offer rebates.)
Tankless can still come out ahead on total cost of ownership because it lasts longer. If a tankless unit runs 20 years and you’d otherwise buy two tanks in that time, the second tank purchase (roughly $1,000 to $2,500 in today’s money) counts toward tankless payback.
Lifespan and long-term value
| Type | Typical lifespan | What shortens it | Typical tank/heat-exchanger warranty |
|---|---|---|---|
| Gas tank | 8 – 12 years | Sediment, failed anode rod, hard water, high pressure | 6 – 12 years (tank and parts); labor often 1 year or none |
| Electric tank | 10 – 15 years | Same, plus element burnout from sediment | 6 – 12 years |
| Tankless (gas or electric) | 20+ years | Scale buildup, skipped descaling, poor water quality | Heat exchanger commonly 10 – 15 years; parts ~5 years |
DOE notes that most tankless heaters have a life expectancy of more than 20 years and use easily replaceable parts, compared with 10 to 15 years for storage tanks. Tankless warranties vary by brand and often require professional installation and registration, and some reduce coverage if you don’t descale in hard water areas. Read the warranty terms before you buy. Our water heater lifespan guide covers warning signs that a tank is near the end.
Flow rate (GPM) and temperature rise by climate
This is the factor that decides whether a tankless unit will satisfy your household. A tankless heater’s capacity is measured in gallons per minute (GPM) at a given temperature rise: the difference between your incoming groundwater and the temperature you want at the tap (usually 120°F).
The colder your groundwater, the bigger the rise and the fewer gallons per minute the unit can deliver. DOE says a 70°F rise is often achievable at about 5 GPM for gas tankless units and only about 2 GPM for electric units.
| Region (winter design inlet temp) | Rise needed for 120°F | 199,000 BTU gas tankless (approx. max GPM) | 27 kW electric tankless (approx. max GPM) |
|---|---|---|---|
| Northern states, e.g. MN, WI, MI, ME (~40°F) | 80°F | ~4.7 | ~2.3 |
| Mid-latitude states, e.g. OH, PA, MO, VA (~50°F) | 70°F | ~5.4 | ~2.6 |
| Southern California, Southwest, Gulf states (~60°F) | 60°F | ~6.3 | ~3.1 |
| South Florida, Hawaii (~70–75°F) | 45 – 50°F | ~7.6 – 8.4 | ~3.7 – 4.1 |
The regional inlet temperatures are winter rules of thumb from Ruud and Rinnai sizing guidance. GPM figures are calculated with the standard formula (GPM = BTU input × efficiency ÷ (500 × temperature rise)), assuming 0.95 efficiency for the gas unit; electric figures use 27 kW × 3,412 BTU/kW. Rinnai’s own groundwater chart for its 199,000 BTU RX199 shows a similar spread, from about 4.6 GPM at 35°F groundwater to about 8.1 GPM at 72°F.
What that means in practice: a standard showerhead is limited to 2.5 GPM under federal rules, and WaterSense showerheads use 2.0 GPM or less. In a northern state, one 27 kW electric tankless unit can comfortably run about one shower at a time in winter. A 199,000 BTU gas unit can handle two showers at once in most of the country. To check your exact numbers, use our guide to what size water heater you need.
The “cold water sandwich” and other tankless quirks
Tankless units have a few behaviors that surprise people who’ve only owned tanks:
- Cold water sandwich. If you turn off the shower and turn it back on a minute later, you can get hot water (left in the pipes), then a short burst of cold while the unit re-fires, then hot again. Recirculation systems and small buffer tanks reduce this.
- Minimum flow rate. Most units won’t fire until flow reaches about 0.4 to 0.5 GPM. A trickle from a low-flow faucet may stay cold.
- Wait time. Tankless doesn’t deliver hot water to the tap any faster. You still wait for cold water in the pipes to clear, plus a few seconds for the unit to ignite. A recirculation pump (built into some models) solves this at the cost of some energy use.
- Simultaneous use. Running the dishwasher or washing machine during a shower can push an undersized unit past its GPM limit, dropping the shower temperature.
- Power outages. Gas tankless units need electricity for controls and the fan, so they stop working in a power outage. Many gas tanks with standing pilots keep heating without power.
Tanks have their own quirk: you can run out. A 40-gallon tank after three back-to-back showers may leave the fourth person with lukewarm water until it recovers.
Space and installation location
Tankless heaters mount on a wall and are roughly the size of a carry-on suitcase, freeing up the 2 to 3 square feet of floor a tank occupies. Many gas models can be installed outdoors in mild climates, which also frees up the utility closet and removes indoor venting. That makes tankless popular in condos, townhouses and small homes.
Tanks need floor space, clearance, a drain pan in many locations and, in seismic zones such as California, earthquake straps. Moving to a larger tank can be impossible in a tight closet, which is one reason homeowners with growing families switch to tankless.
Maintenance requirements
| Task | Tank | Tankless | Typical pro cost |
|---|---|---|---|
| Flush sediment | Once a year | — | $100 – $200 |
| Descale heat exchanger | — | Once a year; every 6 months in very hard water | $150 – $300 |
| Inspect/replace anode rod | Every 3 – 5 years | — | $50 – $300 |
| Clean inlet water filter | — | Several times a year | DIY |
| Test T&P valve | Once a year | Once a year (if fitted) | DIY |
Hard water is the big variable. Scale (mostly calcium carbonate) insulates the tankless heat exchanger, cuts efficiency and triggers error codes. If your water is above about 7 grains per gallon, budget for annual descaling or a water softener or scale-reduction system. Tank owners should follow our step-by-step guide on how to flush a water heater.
Who should choose a tank water heater
- You want the lowest upfront cost. A like-for-like tank swap is almost always the cheapest option, often done in a few hours.
- Your heater just died. Emergency replacements are faster with a tank because no gas, vent or electrical upgrades are needed.
- You may sell within 5 to 7 years. You likely won’t recover tankless conversion costs through energy savings in that time.
- You have very hard water and don’t want annual descaling.
- You’re on electricity in a cold climate. An electric tank (or better, a heat pump tank) handles high winter demand without a massive electrical upgrade.
- Your household uses lots of hot water at predictable times. A properly sized tank with a good first-hour rating serves several showers in a row well.
Who should choose a tankless water heater
- You plan to stay 10+ years. The longer lifespan and lower energy use add up over time.
- You already have adequate gas service. If your gas line and meter can handle ~199,000 BTU, the conversion cost drops sharply.
- You’re short on space. Wall-mount or outdoor installation frees up a closet.
- You run out of hot water. Large families, soaking tubs or back-to-back showers benefit from continuous supply (if the unit is sized for your peak GPM).
- Your hot water use is low or irregular. DOE’s figures show the biggest percentage savings for homes using 41 gallons a day or less.
- You live in a warm climate. Warmer groundwater means more GPM from the same unit, and electric tankless becomes more practical.
Consider a heat pump water heater too
If you’re on electricity, the choice isn’t just tank vs tankless. A heat pump water heater typically uses a fraction of the electricity of a standard electric tank and usually pays back fastest. It needs space (often a room of around 700 cubic feet or a vented closet) and works best in a garage or basement that stays above roughly 40°F to 50°F. See our heat pump water heater cost guide.
Side-by-side decision checklist
| Your situation | Better choice |
|---|---|
| Budget under $2,000 and heater failed today | Tank |
| Gas home, staying 10+ years, adequate gas line | Tankless (condensing) |
| Electric home, cold climate, 100–150 amp panel | Heat pump tank or electric tank |
| Electric home, warm climate, 200-amp panel, 1–2 people | Electric tankless is reasonable |
| Family of 5+ running out of hot water, gas available | Tankless or a larger/high-recovery gas tank |
| Very hard water, no softener | Tank (or tankless with a softener and annual descaling) |
| Condo or tiny utility closet | Tankless |
| Frequent power outages | Gas tank with standing pilot |
If your existing tank is leaking right now, start with our water heater leaking guide to stop damage first, then compare options. If the heater still works but has a problem, check the water heater repair cost guide before replacing.
FAQs
Is a tankless water heater worth it?
It can be if you plan to stay in the home for 10 or more years, have gas service that can handle the unit, and the installation doesn’t need expensive gas line, venting or electrical upgrades. Energy savings typically run tens of dollars to around $100 a year, so the longer lifespan and continuous hot water are usually bigger reasons to buy than the bill savings.
What is the downside of a tankless water heater?
The main downsides are higher upfront and conversion costs, a limited flow rate that can struggle with several fixtures at once in cold climates, annual descaling in hard water, the “cold water sandwich” effect, and gas models not working during power outages.
How long do tankless water heaters last compared to tank?
DOE estimates most tankless units last more than 20 years, versus about 10 to 15 years for storage tanks. Regular descaling is the main factor in reaching that lifespan.
Do tankless water heaters really save money?
They save energy, but the dollar amount is modest. DOE estimates 24% to 34% energy savings for homes using 41 gallons a day or less and 8% to 14% for homes using around 86 gallons. Consumer Reports’ testing showed savings of roughly $45 to $50 a year versus comparable tanks at the prices it used.
How much does it cost to convert from a tank to a tankless water heater?
Expect roughly $3,900 to $6,000 for a typical same-fuel conversion and up to $10,500 or more if you need a new gas line, new venting, or an electrical service upgrade. A simple tankless-for-tankless replacement is far cheaper, typically $1,400 to $3,900.
Can one tankless water heater run a whole house?
A whole-house gas unit rated around 180,000 to 199,000 BTU can usually run two showers at once in most US climates. Homes with three or more bathrooms in use at the same time, or in very cold regions, may need two units linked together or a tank instead.
Do you run out of hot water with a tankless water heater?
No, you won’t run out the way you can with a tank, but if you exceed the unit’s GPM capacity the water temperature will drop. Proper sizing for your peak simultaneous use prevents this.
Is tankless better for a family of 4?
A family of four can be well served by either a 50-gallon tank or a whole-house gas tankless unit. Tankless makes sense if showers often overlap or happen back to back and you have adequate gas service; a 50-gallon tank with a first-hour rating around 65 to 80 gallons is cheaper and works well for most families of four.
Does a tankless water heater increase home value?
Buyers may see tankless as an upgrade, but there’s no reliable data showing it adds more value than it costs. Treat it as a comfort and efficiency upgrade rather than an investment you’ll recover at sale.
Do tankless water heaters need maintenance?
Yes. Most manufacturers recommend descaling the heat exchanger about once a year (more often in hard water) and cleaning the inlet filter. A professional descale typically costs $150 to $300.
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