Tank vs Tankless Water Heater

A tank heater keeps 40 to 50 gallons hot all day and loses some heat while it waits. A tankless unit heats water only when you open a tap, so it avoids that standby loss. The Department of Energy says tankless models are 8% to 34% more efficient, last about 20 years against 10 to 15 for a tank, and cap output at roughly 2 to 5 gallons per minute.

Installed prices explain why many people hesitate. HomeGuide lists tank units at $600 to $3,100 installed and tankless at $1,400 to $5,600. ENERGY STAR estimates a gas tankless saves a family of four about $95 a year versus a standard gas tank. The calculator shows whether your numbers pay back.

Tank vs Tankless Water Heater side by side

Last verified October 2026. Typical values; individual animals, products and local prices vary.

Which one fits you

Tank

• You want the lowest purchase and installation cost, from about $600 up.
• Your household uses a lot of hot water at once and you want a big reserve.
• You rarely stay in a home long enough to recover a higher purchase price.
• You have a limited budget and no spare gas or electrical capacity for a tankless unit.

Tankless Water Heater

• You plan to stay 15 to 20 years and want a unit that can last about that long.
• You want to eliminate standby heat loss and the risk of a tank leak.
• You are short on space and want a compact unit that frees up closet room.
• Your hot-water demand is modest enough that 2 to 5 gallons per minute covers it.

How this works

This page compares the two heater types using Department of Energy and ENERGY STAR guidance and HomeGuide cost ranges. Fuel type, climate, inlet water temperature and household size all move the numbers, so your own bills are the best input.

The calculator adds installed cost to yearly energy cost for each heater. It does not include replacement of a tank during a long period, rebates, tax credits, or descaling service, all of which can shift the result. Use your own gas or electric bills and an installer's quote to replace the defaults and see how payback shifts.

Gas models. Installed costs are the midpoints of HomeGuide's ranges (tank $600 to $3,100, gas tankless $1,600 to $5,600); tank energy of $335 is the midpoint of HomeGuide's $250 to $420; the 21% gain is the midpoint of DOE's 8% to 34%. Replacement costs are not included.

Where these numbers come from

The figures and defaults on this page are based on:

• U.S. Department of Energy: Which Water Heater Is Right for You?, Lifespan, efficiency range and output limits for tank vs tankless. (checked October 2026)
• ENERGY STAR: Gas Tankless Water Heaters, Estimated $95 annual savings and 20-year life expectancy. (checked October 2026)
• HomeGuide: Water Heater Installation Cost, Installed cost ranges, lifespan and annual operating costs. (checked October 2026)
• HomeGuide: Tankless Water Heater Cost, Gas and electric tankless installed cost ranges. (checked October 2026)

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