Free tool
Tankless saves on gas. Hard water sends its own bill.
Most tankless pitches stop at the fuel savings. This one keeps going: the install, the roughly $120-a-year descale Valley water demands, and the replacement tank you'd buy either way. For some households the answer is keep the tank, and when it is, the calculator says so.
- LicensedROC #340524
- InsuredFully covered
- BondedWork guaranteed
- 24/7 ServiceEvery day
Valley hard water retires most tanks around year ten.
Phoenix-metro residential gas runs about $1.40/therm.
Stay with a tank — 10-year cost
$4,228
$243/yr in fuel, plus the replacement tank you buy when this one dies.
Switch to tankless — 10-year cost
$6,119
$162/yr in gas, plus $120/yr descaling.
10-year extra cost of tankless
$1,891
Payback point
None within 20 years
Keep the tank.
At your usage, the fuel savings do not cover the annual descale, let alone the $1,500 upfront gap. A $1,800 tank is the economic answer here, and it is not close — you would be roughly $1,891 worse off over ten years. Buy tankless for endless showers if you want them. Just do not buy it for the math.
The assumptions
- Tank: $1,400–$2,200 installed (we use the $1,800 midpoint), ~0.60 UEF for gas, ~0.92 for electric, and a ~10-year working life in Valley hard water.
- Tankless: $2,800–$3,800 installed (midpoint $3,300), ~0.90 UEF gas condensing, ~20-year life with an annual descale at about $120.
- Hot water demand: 17 gallons per person per day at typical usage, heated through a ~67°F rise. Light and heavy usage scale that by 0.7× and 1.3×.
- If your current heater is electric, the tankless option is still modeled as gas — that is what gets installed here. If your home has no gas line, add the cost of running one before trusting the payback figure.
- Fuel prices are held flat for ten years. They will not be, but guessing the direction is astrology, not arithmetic.
Either way the math falls, we install both. See tankless installation or standard water heaters for flat pricing.
What the ten-year line is telling you
Ten years is long enough for the gap to settle. Tankless wins or loses on one trade: a lower fuel bill against a higher install cost. If the savings line is positive and payback lands inside seven years, the switch is an investment rather than a comfort purchase, and the unit still has a decade left when a tank would be due for its second replacement. The long version of this arithmetic is in Tankless vs. Tank.
A negative number is worth believing. Electric households see it most often, because the fuel math assumes a gas unit, and running a new gas line to the garage can eat the payback whole. A close result is a true tie. Decide on endless hot water, not on money, because the money is a wash. Either way, a water softener upstream shrinks the descale problem for tank and tankless alike.
What the model can't see is the heater you already own. A twelve-year-old tank in a Phoenix garage is living on borrowed time, and replacement timing moves this math more than any rate input. The noises and drips of an aging tank will tell you roughly how much time is left. Better to decide now, with the assumptions on screen, than on the afternoon it fails, with a stranger in your garage waiting for a yes.
Free estimate
Get both options quoted.
We size and quote tank and tankless side by side, flat and in writing. If a tank is the better buy for the way your household uses hot water, that is the one we’ll recommend.
- Flat price, agreed before work starts
- Licensed, insured & bonded · ROC #340524
- Emergency dispatch 24/7
- Veteran owned & operated