Tankless or Tank Water Heater: Which Fits Your Home?

What is the real difference between them?

A storage tank heater holds 30 to 80 gallons of water and keeps it hot all day, so hot water is waiting the moment you open a tap. The downside is what the DOE calls standby heat loss: the tank loses heat into the room even when nobody is using water, and the burner or elements cycle on to make it up.

A tankless, or on-demand, heater has no reservoir. When a hot tap opens, water flows through a heat exchanger and a gas burner or electric element fires to heat it on the way through. When the tap closes, it shuts off. There is nothing to keep warm, so there is no standby loss, but output is limited by how fast the unit can heat water flowing through it.

How do they stack up?

The installed ranges overlap more than many people expect, but the tankless figure is for the unit and standard installation. Converting from a tank often adds work, covered below.

Does tankless actually save money each month?

It saves some, and how much depends on your household. The DOE says an ENERGY STAR certified tankless model could save $100 or more a year. That savings comes from cutting standby loss, so households that use less hot water tend to see a larger percentage gain, while busy households that run hot water much of the day see less.

For context, HomeGuide puts the yearly operating cost of a standard gas tank at $250 to $420 and a standard electric tank at $530 to $600. A heat pump electric tank comes in at $160 to $190 a year, which is worth knowing if you don't have natural gas: for an all-electric home, a heat pump tank can be a stronger efficiency upgrade than an electric tankless unit.

Spread over a longer life, the yearly savings help close the price gap, but a tankless unit rarely pays for itself quickly if the conversion is expensive. If your current tank still works, there is little reason to rush.

Can one tankless unit run two showers at once?

This is the question that matters most. The DOE puts typical tankless output at about 2 to 5 gallons per minute. A modern showerhead, a dishwasher and a washing machine running at the same time can ask for more than one unit can heat, especially in winter when the incoming water is colder and the heater has to raise it further. The DOE notes that homes with heavy simultaneous demand may need two units, or a point-of-use heater for a far bathroom.

Count your peak moment. If the busiest hour in your house is two showers plus the dishwasher, size for that, not for the average day. A plumber who installs tankless water heaters in Raleigh will ask about fixtures and flow rates before recommending a model, and you should be wary of anyone who doesn't.

What does switching from a tank involve?

Replacing tank with tank is mostly a swap: the venting, gas line or circuit are already there. Going tankless can mean more:

• Gas supply. A gas tankless unit burns far more gas while running than a tank burner, so the existing line may need to be upsized. A plumber who does gas piping work can check the line and meter capacity.
• Venting. Many gas tankless units vent differently from the tank they replace. HomeGuide puts first-time venting at $500 to $1,500 and replacement venting at $100 to $600.
• Electric capacity. Whole-house electric tankless units draw a lot of current, and older panels may not have room. Get that checked before you buy.
• Changing fuel. HomeGuide lists an electric-to-gas conversion at $400 to $2,000 or more, and gas-to-electric at $250 to $1,000 or more.
• Permits. Fuel and venting changes generally need a permit. Raleigh handles these through its online Permit and Development Portal, with a Permit Helpline at 919-996-2500.

How does upkeep compare?

Neither type is maintenance-free. A tank benefits from a yearly flush to clear sediment and an occasional look at the anode rod, the sacrificial part that slows rust inside the tank. HomeGuide prices a professional anode replacement at $150 to $350. A tankless unit needs its heat exchanger flushed on the schedule in the owner's manual, and its inlet filter cleaned. Repairs also cost more when something does break: HomeGuide's 2026 repair guide puts typical tankless repairs at $300 to $1,300, compared with $150 to $700 for a tank. That gap is worth weighing against the longer life. Whichever you choose, register the unit with the manufacturer and keep the receipt, since warranty coverage often depends on proof of installation and maintenance.

Gas, propane or electric: which applies to your house?

Natural gas

Most of Raleigh and the rest of Wake County is in Enbridge Gas North Carolina's territory, the utility formerly known as PSNC, though gas is not on every street. Piedmont Natural Gas serves parts of Johnston, Harnett, Wayne and Nash counties. If you already have gas to the water heater, a gas tankless unit is usually the most straightforward conversion.

Propane

Homes out past the gas mains, common in rural parts of Johnston and Harnett counties, can run a propane tankless unit. The same sizing, line and venting questions apply.

Electric

Electric tankless works best for smaller homes, low-demand households, or a single far-off bathroom. For a whole family in an all-electric house, compare it against a heat pump tank before deciding.

Does Raleigh's water make a difference?

Scale is the enemy of tankless heat exchangers, because minerals in hard water coat the narrow passages and cut efficiency. Raleigh Water is soft, with total hardness around 25 parts per million in its 2025 water quality report, which is a point in favor of tankless for homes on city water in Raleigh and the merger towns such as Garner and Knightdale. Follow the manufacturer's flushing schedule anyway. On a private well, test the water first; Wake County notes that more than 40,000 households county-wide use wells and encourages regular testing. If the results show hard water, budget for a softener, and look into softener installation alongside the heater.

So which should you choose?

A tank makes sense if your current tank setup works, your budget is tight right now, several people use hot water at the same time, or you just need hot water back quickly after a failure. You can read our guide to repairing versus replacing a heater if yours has just quit.

Tankless makes sense if you plan to stay in the house long enough to benefit from a 20-year life, you have gas available, you want the floor space back, or your household's demand fits inside one unit's flow rate.

Either way, ask for a written quote that lists the unit, any gas, venting or electrical changes, the permit and haul-away of the old tank. If you're replacing a tank like-for-like, see tank replacement in Raleigh. Homeowners south of the city can also look for help in Fuquay-Varina or Apex, and you can browse every town we connect callers in.

A note on gas safety

If you smell gas near a water heater, leave the house and call 911 or the utility from outside. For Enbridge Gas North Carolina, call 1-877-776-2427. For Piedmont Natural Gas, call 800-752-7504. Do not relight a pilot or operate switches until the utility says it is safe.