What tankless genuinely does better
It does not run out. Water is heated as it passes, so back-to-back showers and a full house of guests are not a problem in the way they are with a tank. For larger households this is often the whole reason.
No standby losses. A tank keeps 40 or 50 gallons hot around the clock whether anyone uses it or not. A tankless unit uses energy only when hot water is drawn. That saving is real, if modest.
Lifespan. A well-maintained tankless unit should reach 15-20 years, against 10-12 for a tank on our water. Components are also more serviceable — a heat exchanger, fan or valve can be replaced, where a corroded tank cannot.
Space and safety. Wall-mounted, roughly the size of a small suitcase, and there is no vessel of water to fail. A tank that lets go puts its entire contents on the floor; a tankless unit cannot.
Summer specifics. In August, incoming water is warm, so a tankless unit is working at its easiest — delivering its highest flow rates — while a tank is standing losing heat into a hot garage all day.
Where tank still wins
Upfront cost, and it is not close. The unit costs more, and the installation frequently costs more again — a tankless heater generally needs a larger gas line, different venting, and sometimes electrical work. Replacing a tank with a tank is often a straight swap.
Simplicity. Fewer parts, fewer sensors, fewer error codes, and any plumber can service one.
Tolerance of neglect. This is the big one locally. A tank that is never flushed loses efficiency and capacity but soldiers on for years. A tankless unit that is never flushed can lose a large share of its lifespan — and the heat exchanger, when it goes, is often enough of the unit's value that replacement makes more sense than repair.
Simultaneous demand. A tankless unit delivers a temperature rise at a given flow rate. Ask for two showers plus a dishwasher in January, when incoming water is cold, and an undersized unit runs out of capacity — where a large tank simply empties more slowly.
Worth knowing
Winter is the honest test for sizing. Incoming water arrives 20-30°F colder, so the same output demands far more heat. A unit sized on summer performance can disappoint in January — and that is a sizing decision, not a fault.
The hard water factor
This deserves its own section because it changes the answer for a lot of houses here.
A tank hides scale. Calcium settles to the bottom, insulates the burner, and costs efficiency — but the tank keeps working while it happens. It is a slow, forgiving failure.
A tankless unit has nowhere to put it. Water passes through a narrow heat exchanger and mineral deposits directly on the surfaces doing the work. Passages constrict, heat transfer falls, and eventually the exchanger is the repair.
On Boerne's 15-30 grains, that means the annual descaling flush is not optional — and twice a year on a well at 25-35 grains.
A properly sized softener changes this materially: it removes most of what forms the scale, stretching the flush interval to every 18 months to two years and protecting the exchanger. If you are seriously considering tankless here, pricing a softener alongside it is the sensible way to look at it.
Things worth getting right at installation
Isolation valves. A pair of service valves with hose ports either side of the unit, so it can be flushed without cutting into pipework. Inexpensive at installation, annoying to retrofit, and their absence is why some units never get flushed at all.
Gas line sizing. A tankless heater draws far more gas while firing than a tank does. An undersized line starves the burner, which is both a performance and a combustion issue. This is one of the most common failings in cheap installations.
Venting. Condensing units produce acidic condensate that must be drained properly and use different venting from non-condensing ones. Not interchangeable.
Sizing on peak simultaneous demand and winter groundwater, not on the number of bathrooms. Ask whoever quotes you what temperature rise the unit delivers at the flow rate you actually need in January.
Which one to choose
Tankless suits you if: you run out of hot water regularly, you want the space back, you plan to stay in the house long enough for the longer life to matter, and you will genuinely keep up with annual servicing — or you have a softener.
Tank suits you if: upfront cost matters most, the existing setup works and you are simply replacing at end of life, the house has modest hot water demand, or you know maintenance is not going to happen.
That last point is not a criticism. Plenty of good reasons exist for a household not to keep to an annual service schedule, and choosing equipment that suits how a house is actually run beats choosing what performs best on paper.
We fit both, and we will tell you which one your house and habits actually point to.