A tank water heater keeps a supply of hot water ready and costs less to install. A tankless heater heats water only when you use it, so it does not run out and it usually lasts longer, but it needs a large enough gas line, the right venting and regular descaling if your water is hard. For many New Jersey homes on well water, the choice comes down to your gas line, your water quality and how much hot water you use at once.
How each type works
Tank water heaters hold heated water, often 40 to 80 gallons, and keep it hot all day. When you use hot water, cold water fills the tank and gets heated. When the tank runs low, you wait for it to recover.
Tankless water heaters have no tank. When you open a hot tap, water flows through a heat exchanger and a burner heats it right away. According to a U.S. Department of Energy Building America guide, a tankless unit needs a minimum flow, about 0.5 gallons per minute, to turn on.
Side by side
How long they last
Rheem says tank heaters usually last about 8 to 12 years, and tankless units often last 15 to 20 years or more. The DOE Building America guide lists tankless life at more than 20 years, compared with 10 to 15 years for traditional tanks. Maintenance makes a big difference for both.
Hot water supply
A tank gives you what is stored, then you wait. A tankless unit keeps going as long as you need, but only up to its flow rating. If two showers, the dishwasher and the washer all run at once, a unit that is too small will not keep up. That is a sizing question, and it matters more in winter when the incoming water is colder.
Energy use
A tank loses some heat all day just keeping water hot, which is called standby loss. Tankless heaters avoid that. The DOE Building America guide estimates tankless savings in the range of 10 to 20 percent, but real savings depend on how your household uses hot water.
Space
A tankless unit hangs on the wall and frees up floor space. That can matter in small basements and utility closets.
Up front cost
Tankless installs usually cost more because of the unit, venting and often gas line work. A straight tank for tank swap is usually the simplest job.
Hard water and descaling
This is the big one for well homes in our area. The DOE guide notes that when water has high mineral content, scale is likely to build up in a tankless heat exchanger, and the coils should be flushed with a descaling solution. The USGS explains that hard water forms scale when heated, which lowers water heater efficiency.
What that means for you:
- If you go tankless on hard well water, plan on regular descaling. How often depends on your hardness and use, so follow the maker's guidance.
- Ask for isolation valves when it is installed. They make flushing much easier.
- Think about a water softener or scale treatment ahead of the heater. It protects the tankless unit and your fixtures too. See our water softeners and filtration page.
- Tanks suffer from hard water too. The sediment just collects on the bottom instead, which is why yearly flushing helps.
Gas line sizing and venting
A gas tankless heater burns a lot of gas for a short time. Its burner is often much larger than a tank heater's. That means:
- Your gas line may need to be bigger. The pipe from your meter has to carry enough gas for the tankless unit plus your boiler or furnace, stove, dryer and anything else, all at once. An undersized line can cause the heater to shut down or not heat well. Your gas meter and service may also need to be checked with the utility.
- It needs the right vent. Most condensing tankless units vent through a side wall with plastic pipe. Non-condensing ones may need special stainless steel venting. The DOE guide notes that venting can be expensive and suggests putting the heater on an outside wall to keep the vent run short.
Gas line and venting work must be done by a licensed professional and inspected. Our gas line installation page explains more. If you ever smell gas, leave the house and call your gas utility from outside.
Which one fits your home?
A tank often makes sense if:
- You want the lowest up front cost and the simplest swap.
- Your gas line is small and upsizing would be a big job.
- You have very hard water and do not plan to treat it.
Tankless often makes sense if:
- You run out of hot water with a tank.
- You want to free up space or plan to stay in the home a long time.
- Your gas service can support it, and you will keep up with descaling or treat your water.
If you heat with a boiler, a combi boiler or an indirect tank are two more options worth a look. We cover both on our tankless water heaters page.
When to call a licensed plumber
- You are replacing a heater and want help sizing a tankless unit or a new tank.
- Your tankless unit shows an error code, cycles on and off, or gives you lukewarm water.
- You want your gas line checked before adding a tankless heater.
Why this happens around Budd Lake and Morris County
Many homes here are on private wells with hard water, which makes descaling a real part of owning a tankless heater. Our winter ground water is cold, so a tankless unit has to work harder in January than in July. And many 1970s to 1990s homes in Mount Olive, Roxbury, Randolph and Hackettstown were piped with gas lines sized for a boiler, a tank heater and a range, not for a large tankless burner on top of that.
Frequently Asked Questions
Do tankless water heaters really never run out?
They do not run out the way a tank does, but they have a flow limit. If you use more hot water at once than the unit is rated for, the water will cool off.
How often does a tankless water heater need descaling?
It depends on your water hardness and how much hot water you use. On hard well water, plan on regular flushing, and follow the maker's schedule.
Can I put a tankless heater on my existing gas line?
Sometimes, but often not. A licensed plumber has to add up the gas demand of all your appliances and check the pipe size and length.
Which lasts longer, tank or tankless?
Tankless usually lasts longer. Rheem gives about 8 to 12 years for tanks and 15 to 20 or more years for tankless units.
If you want a second set of eyes on it, call or text us at 862-362-0634 or request service online. We are a family owned shop in Budd Lake, and we will tell you straight what we find and what it needs.
Sources
- U.S. Department of Energy Building America: Tankless Water Heaters
- Rheem: Water Heater Lifespan, When to Repair vs. Replace
- USGS: Hardness of Water
Micky Cipolla is a New Jersey licensed master plumber (License #13478) with more than 15 years in plumbing and heating. He owns Tucker's Plumbing in Budd Lake and works on homes across Morris County every day. Verify the license.