The short answer
A tank water heater is cheaper to install ($1,800–$3,500 in our area), simple to replace and works with any gas line. A tankless unit costs two to three times more up front ($4,000–$7,500 installed), saves floor space and standby energy, lasts nearly twice as long — but needs a large gas supply and struggles to deliver high flow when Massachusetts groundwater is near 40°F in winter. If you already have a boiler, an indirect tank is often the best of both. The right answer depends on how many people shower at once and what your basement already has.
What do they cost to install and run?
| Tank (40–50 gal gas) | Tankless (gas, condensing) | |
|---|---|---|
| Installed cost, like-for-like | $1,800 – $3,500 | $4,000 – $7,500 |
| Conversion extras | — | Gas line upsizing, new venting, condensate drain, outlet: often $800 – $2,500 more |
| Typical lifespan | 8 – 12 years | 18 – 20 years |
| Energy factor (UEF) | 0.60 – 0.70 | 0.90 – 0.96 |
| Annual fuel savings vs. a standard tank | — | Roughly $100 – $200 for a typical family |
| Maintenance | Flush yearly | Descale yearly (more with hard water) |
On paper the tankless unit pays back its premium over its longer life, and Mass Save rebates on qualifying condensing units narrow the gap further. In practice the payback depends heavily on the conversion extras — a house that already has a large gas line and an easy exterior wall for venting is a much better tankless candidate than one that needs a new gas run from the meter.
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How much hot water do you actually get in January?
A tank stores hot water; a tankless heater makes it on demand, raising incoming water to your set temperature as it flows. Its output is rated in gallons per minute at a given temperature rise. In Massachusetts the incoming water is around 40°F in winter, so a 120°F shower needs an 80°F rise — and a unit that delivers 9 GPM in a Florida brochure delivers roughly 5 GPM here.
Five gallons a minute is one shower and a running kitchen faucet. Two showers plus a dishwasher will drop the temperature or trip the unit into flow limiting. The fix is sizing: for most family homes in the Boston area we install units in the 180,000–199,000 BTU class, and we check that the gas meter and piping can actually feed that plus the boiler at the same time. Undersized gas supply is the number one reason tankless owners are unhappy.
A tank has the opposite profile: a 50-gallon unit with a good recovery rate handles a busy morning easily, then costs money keeping that water hot all day whether anyone uses it or not.
What about space, venting and gas supply?
- Space. A tankless unit hangs on the wall the size of a carry-on suitcase, freeing several square feet in a tight basement or utility closet.
- Venting. Condensing tankless units side-vent in PVC through a wall and need a condensate drain. Atmospheric tanks vent up the chimney; if the boiler has already left the chimney for a condensing unit, the tank may need a chimney liner — another reason to look at both appliances together.
- Gas. A tank burns 30,000–40,000 BTU. A whole-house tankless burns up to 199,000. Many older homes need the gas line upsized from the meter, which is a real cost and sometimes a utility upgrade.
- Power. Tankless needs an outlet for the controls and fan; tanks do not. In an outage, a gas tank still makes hot water; a tankless does not (unless on a battery backup).
- Water quality. Hard water scales tankless heat exchangers. Much of the North Shore has moderately hard water; annual descaling or a small softener keeps the unit efficient.
What about an indirect tank?
If your home heats with a boiler, you have a third choice that often beats both: an indirect water heater. It is a heavily insulated storage tank with a coil inside; the boiler circulates hot water through the coil and heats the domestic water without a separate burner, flue or gas line. Recovery is fast (the boiler is far more powerful than a tank burner), standby loss is very low, there is nothing to vent, and the tanks routinely last 15–20 years. Installed cost is typically $2,800–$4,500. We install indirects alongside boiler replacements constantly — the photo at the top of this article is exactly that pairing.
Which one is right for your house?
- Choose a tank if budget is the priority, the existing setup is simple, you lose power occasionally, or the house is small with modest hot-water use.
- Choose tankless if space is tight, gas supply and an exterior wall are already there, you value the long life and lower running cost, and you accept sizing it for winter flow.
- Choose an indirect if you have (or are about to install) a boiler. It is the quiet winner for most boiler-heated homes on the North Shore.
Not sure what your basement can support? Precision Plumbing Solutions sizes and installs all three across Essex, Middlesex, Suffolk, Norfolk and Plymouth Counties. See water heater installation and repair, or if the boiler is due as well, what boiler replacement costs in Massachusetts.
Questions people ask
How long do tank and tankless water heaters last?
A tank typically lasts 8–12 years in Massachusetts water; a tankless unit 18–20 years with annual descaling. Longevity is a big part of the tankless value case.
Will a tankless unit run two showers at once?
A properly sized unit (roughly 180,000–199,000 BTU for a family home here) usually will. An undersized one, or one fed by a gas line that is too small, will not — that is the most common tankless complaint we fix.
Can I switch from a tank to tankless?
Yes. The install usually involves upsizing the gas line, new venting through a wall, a condensate drain and an electrical outlet, which is why the conversion costs more than the unit itself.
What is an indirect water heater?
A storage tank heated by your boiler instead of its own burner. If you already have a boiler, it is often the most efficient and reliable option, with no separate venting.
