It’s 6:45 on a January morning in West Haven. One shower is running, someone is waiting on the next one, and the dishwasher is halfway through its cycle. The water coming in from the main is a lot colder than it was in July, and the furnace has been cycling since before dawn. That’s the morning to picture when you weigh a tank vs tankless water heater, because a water heater earns its keep on the coldest, busiest day of the year.
Between them, space heating and water heating accounted for about 61% of the energy U.S. homes used in 2020, according to the U.S. Energy Information Administration’s household survey. In a gas-heated house the water heater and the furnace also share a gas line and peak on the same mornings. Before a bigger water heater goes in, count the furnace’s gas use in the sizing. In West Haven, Comfort Solutions services furnaces as well as water heaters, so one company can check both.
The sections below compare the two types on what matters in a northern Utah winter: hot water at peak demand, hard water, altitude, space, the gas line and long-term cost.
How a tank and a tankless water heater make hot water
A storage tank heats a fixed volume of water, often 40 or 50 gallons, and keeps it hot around the clock. That readiness has a cost. The tank loses heat through its walls all day, a drain known as standby loss, so the burner fires even when nobody is using water.
A tank’s real limit is its first-hour rating, the number of gallons of hot water it can deliver in an hour starting full. Once those gallons are gone, everyone waits while the burner catches up.
A tankless unit stores almost nothing. Opening a hot tap sends cold water into the unit, the burner fires, and a heat exchanger warms the water on its way through. The U.S. Department of Energy says tankless units typically deliver 2 to 5 gallons per minute, with gas models producing higher flow rates than electric ones.
Tanks are rated in gallons. Tankless units are rated in gallons per minute. Moving from one type to the other usually changes the gas line, the venting and the plumbing. Treat it as a full water heater installation and price it that way.
Why a Utah winter is the real test for tankless
A tankless heater has to lift incoming water to its set temperature in the few seconds that water spends inside it. Plumbers call that gap the temperature rise. The colder the water coming in, the bigger the rise and the lower the flow a unit can sustain.
Rinnai’s groundwater temperature map shows how much that matters. Most of Utah falls in its 47-degree band, with a colder 42-degree pocket in the north. The map also notes that actual inlet temperatures can shift with local conditions and the seasons. Rinnai’s chart gives a 199,000 Btu unit a maximum flow of 5.2 gallons per minute with 47-degree groundwater and 4.4 gallons per minute at 35 degrees. Feed the same unit 77-degree water, the warmest band on the map, and it reaches 8.8.
The DOE has warned that “taking a shower and running the dishwasher at the same time can stretch a tankless water heater to its limit.” January is when that limit sits lowest. Size a unit on mild-weather water and the second shower can run lukewarm on the coldest mornings. A unit that shuts off mid-shower is a different problem, usually a safety control shutting the burner down, and worth a service call.
A tank handles the same morning differently. It never limits the flow, so the first showers come out at full temperature. Its weak spot is the shower that starts after the stored gallons run out, while the burner is still catching up.
Hard water and altitude change the math
Northern Utah’s water is hard. Weber Basin Water Conservancy District supplies treated water to cities and water districts across the region. Its 2025 water quality report tells customers that hardness can range from 10 to 18 grains per gallon, or 171 to 308 parts per million. The U.S. Geological Survey classes anything above 180 milligrams per liter as very hard and notes that heated hard water leaves calcium carbonate deposits inside a home water heater.
Both types pay for it, in different places. A tank collects sediment on its bottom, which is why plumbers recommend flushing it. A tankless unit takes the hit in its narrow heat exchanger. A.O. Smith says mineral scale there reduces efficiency and restricts water flow, and it lists annual descaling as standard upkeep for tankless units without a scale-prevention system. It’s the same limescale that crusts showerheads, building up where you can’t see it.
Elevation is the second Utah factor. West Haven and Ogden sit above 4,000 feet, and thinner air changes how much heat a gas burner delivers. Rinnai approves its SENSEI RX condensing units for installs up to 10,200 feet. Its spec sheet still notes that maximum flow rates “may vary based on set temperature, Delta T and altitude.” A sizing chart that assumes sea level can overstate what a unit will deliver here, so ask whoever sizes yours to account for elevation.
Footprint, the gas line and venting
Space is the easy win for tankless. A tank and its drain pan claim a closet corner, while a tankless unit mounts on a wall. Where it goes still matters, because placement decides the venting route, how well the unit is protected from freezing, and how long you wait for hot water at the tap.
Fuel supply is the catch. Rheem’s gas line guide puts most tankless water heaters at 140,000 to 200,000 BTU or more. That capacity, the guide says, “makes a tankless water heater one of the largest single appliances on a typical gas system.” The guide adds that the gas piping typically has to be upgraded. Venting has to meet local code as well.
That’s where the furnace comes back into the picture, because on a January morning a big tankless burner and the furnace can both fire at once. The gas line and meter have to feed both. If the line was sized for a furnace and an old tank, a new tankless unit can come up short on gas right when the house needs it most.
Tank vs tankless water heater efficiency and lifespan
The long-term numbers favor tankless, though less so in busy households. DOE figures put tankless units at 24% to 34% more energy efficient than conventional storage tanks in homes that use 41 gallons of hot water a day or less. In homes using around 86 gallons a day, the gain drops to 8% to 14%.
Lifespan is the wider gap. The same DOE guidance gives most tankless water heaters a life expectancy of more than 20 years, against 10 to 15 years for a storage tank.
ENERGY STAR’s criteria show the difference at the certified end of each category. A gas tankless heater needs a Uniform Energy Factor of at least 0.95 to qualify, while a medium-draw gas storage tank qualifies at 0.81.
Tankless still costs more up front, and gas line or venting upgrades add to the bill. The efficiency savings only pay that back if you stay in the house long enough to collect them.
So which one wins your winter?
For a northern Utah homeowner staying put for a decade or more, the tank vs tankless water heater question tips toward gas tankless, on two conditions. Size it for January water at Utah elevation. And make sure the gas line can carry it alongside the furnace without shortchanging either one.
A tank is the smarter buy when the budget is tight or the gas service can’t be upgraded without major work. It also wins if you expect to sell before the efficiency gain pays for itself. A properly sized tank with a solid first-hour rating will get a family through a cold morning.
Decide before the old heater decides for you. A replacement planned in the fall can be sized, piped and vented properly. One bought in a hurry on a January morning tends to be whatever’s in stock.
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