Tank or tankless at 7,000 feet?
Both work in Flagstaff when they are chosen and set for the elevation. Both fail when they are not. This page lays out what altitude changes for each, so the choice is yours with the facts in front of you.
Flagstaff Water Heaters LLC · ROC 367669 · Arizona Registrar of Contractors · Licensed, bonded and insured
The one rule that applies to both
Above 2,000 feet, gas appliance input is adjusted downward, per the manufacturer's instructions and the National Fuel Gas Code (NFPA 54, section 11.1.2). Thinner air means less oxygen per cubic foot, so the burner is set to burn less fuel. A tank and a tankless unit both live under that rule. What differs is how much margin each one has left after the adjustment, and how each is set.
Tank water heater
A tank heats slowly and stores the result. The adjusted burner means a slower recovery, so the honest question at elevation is whether the tank size still covers your household's peak hour. Many manufacturers list altitude ratings or sell high-altitude models; Rheem, for example, sells dedicated high-altitude units. The sizing math is done from the manufacturer's altitude table for the exact model, never from a rule of thumb.
Tankless water heater
A tankless unit heats on demand, so the adjusted input shows up as lower flow at a given temperature rise, not as running out. The fit question is whether the unit's altitude-adjusted output still covers your simultaneous demand on a January morning. Some units are set for elevation by a switch; Rinnai models, for example, are adjusted with DIP switches to the manufacturer's elevation band, with no conversion kit. Others have a stated ceiling: A.O. Smith's outdoor tankless line is certified to 6,000 feet, which rules it out for Flagstaff.
Three things that change the price and the day, tank or tankless
Venting
A tank usually reuses a properly sized existing vent. A gas tankless unit almost always needs new venting in the material its manufacturer specifies, and a condensing model needs a drain for the condensate. That is the single biggest reason a tankless conversion takes longer than a tank swap.
Gas supply
A tankless burner draws far more gas while it runs than a tank burner does. The gas line and the meter have to be sized for it, and the manufacturer's table for your elevation is what sets the number. Sometimes the existing line is fine; sometimes it is not, and we tell you which before you decide.
Water quality
Where the water is hard and mineral-heavy, scale builds in a tank's bottom and in a tankless unit's heat exchanger. Either way the answer is the same: a maintenance schedule, a sediment flush for tanks, a descaling flush for tankless units, and an anode check on tanks. We build that into the plan rather than leaving it to chance.
How we help you decide
We ask about your household, how many people shower in the same hour, whether the laundry and the dishwasher run at the same time, how long you plan to stay in the house, and what the current gas line and venting look like. Then we show you the manufacturer's altitude-adjusted figures for a tank that fits and a tankless unit that fits, side by side, with the written price for each. There is no right answer for every house. There is a right answer for yours, and the numbers make it visible.
If the honest answer is that a well-sized tank serves you better, that is what we will say. If the honest answer is tankless, we will say that too. Either way, the unit is chosen from the manufacturer's altitude table, installed on permit, and inspected. Our tankless installation page covers the install itself; the sizing page covers the code.
Tank vs tankless, answered
Does a tankless unit run out of hot water?
Not in the way a tank does. A tankless unit keeps heating as long as water flows, but its flow at a set temperature is limited, and at elevation that limit is lower than the number on the box. Two showers and a dishwasher at once can exceed it. Sizing to your simultaneous demand is the whole job.
Can my existing gas line feed a tankless unit?
Sometimes. It depends on the pipe size, the run length, the meter and what else is on the line. We check it against the manufacturer's requirement before quoting, and the written price says whether the line changes.
Is a tank a worse choice at altitude?
No. A tank sized from the manufacturer's altitude table and installed on permit is a sound choice in Flagstaff. The mistake is installing a unit sized as if the house were at sea level.
What about electric tankless?
Electric units are not affected by the gas input rule, but they draw very large currents and most homes need panel and wiring work to feed one. We will tell you what your panel can support before it becomes an option on the quote.
Two written prices, one honest recommendation
Mon–Fri, 9:00 AM – 5:00 PM · Serving Flagstaff, Williams and Winslow, plus the surrounding high country