Short answer: a tank is the simpler, cheaper swap. A tankless heater is a bigger install that does not run out of hot water. Which one fits depends on your house more than on the heater.
Here is how we think it through with a homeowner.
How each one works
A tank heats 40 or 50 gallons and keeps it hot all day. When the tank is empty, you wait for it to heat again.
A tankless heater has no stored water. It fires a large burner only while a tap is open and heats the water as it passes through. It can’t run out, but it can only heat so many gallons a minute.
Why a tank is the easy swap
A new tank sits where the old one was. It connects to the same gas line, the same vent and the same water pipes. Nothing else in the house changes.
Why tankless is a bigger install
A tankless unit needs four things your old tank did not.
1. A bigger gas line
This is the big one. A tank burns about 40,000 BTU. A whole-home tankless unit burns up to about 199,000 BTU at full fire. The half-inch gas line that fed your tank usually can’t carry that.
So part of the gas line is replaced with larger pipe, back toward the meter. If the meter is on the other side of the garage wall, that is a short run. If it is at the far end of the house, it is a long one. This is the main reason the same heater is a small job in one house and a large one next door.
2. New venting
A tankless unit can’t share the old metal flue. It needs its own vent and air intake, usually run out through a side wall.
3. A condensate drain
High-efficiency units pull so much heat from the exhaust that water condenses inside. That water needs a small drain line.
4. Power
A tankless heater needs a standard outlet for its fan and controls.
Three things that are different in Utah
Hard water. Scale is what wears out both kinds of heater, and Salt Lake Valley water makes a lot of it. In a tank it settles on the bottom. In a tankless unit it clogs the heat exchanger. A tankless heater on hard water needs a flush about once a year, or a water softener ahead of it.
Cold winter water. Water comes into a Utah home very cold in January. A tankless heater has to raise it further, so it delivers fewer gallons a minute in winter than the box suggests. Sizing has to be based on winter.
Altitude. Gas burns with less output at 4,300 feet and up. Both tanks and tankless units are affected, and tankless units have altitude settings that need to be set at install.
A tank is the better fit if
- You want the lowest cost today
- Your current tank keeps up with your household
- Your gas meter is far from the water heater
- The home is all-electric
Tankless is the better fit if
- You run out of hot water
- You have a large tub, or a full house in the mornings
- You want the floor space back
- You plan to stay long enough to benefit from a longer-lasting unit
- You are building new, when the gas line and vent can be sized for it from the start
How to decide for your house
Three questions settle most of it:
- Does your tank run out? If not, a tank is probably still right.
- Where is the gas meter compared with the heater?
- Is the heater on an outside wall, so the vent run is short?
We install both, and we will tell you which one fits. You get a firm price before any work starts. Right now every tankless water heater install comes with a free water softener. For the tank side, see water heater installation.