The Pros and Cons of Using a Tankless Water Heater
Continuous hot water and lower bills, at a higher price
A tankless water heater, also called an on-demand or instantaneous water heater, has no storage tank. It heats water only when a hot tap opens, which is why it has become popular with people who want to save energy and space.
If you are replacing an old heater or planning a new home, the choice comes down to a handful of factors. Some favor the tankless design clearly. Others, such as the purchase price and the limits on flow, can make a conventional tank the better fit.
Pros
Most of the advantages follow from the fact that there is no tank to fill, keep warm, or find room for.
Hot water that doesn't run out
A tank holds a fixed amount of hot water, and once a few long showers have drained it, you wait while it refills and reheats. A tankless unit heats water as it flows through, so it keeps going for as long as the tap is open. For showers, faucets, and appliances, that means no cold surprise at the end of a busy morning, provided the unit can keep up with the flow you ask of it.
Energy efficiency
The heater only runs when someone opens a hot tap. A tank, by contrast, has to stay warm all day whether anyone needs hot water or not. Using less energy usually leads to lower energy bills, though how much you save depends on how much hot water your household goes through.
Space savings
Without a large storage tank, the unit is compact enough to hang on a wall. It fits in places a tank never would, such as a utility closet or even the cabinet under a sink. The floor space a bulky tank used to occupy becomes free for storage or anything else you want to put there.
Longevity
Tankless heaters generally last longer than tank models. That assumes a good installation and regular maintenance, but with both in place you can expect reliable hot water for many years before replacement comes up.
Less risk of water damage
When a tank leaks or ruptures, its full contents can end up on your floor. A tankless heater stores very little water, so the worst case is much smaller. Many homeowners find that reassuring, and some may see it reflected in lower insurance premiums, though that is not guaranteed.
No waiting for a tank to reheat
Because water is heated as it passes through, you never wait for an emptied tank to warm up again. In that sense hot water is available almost immediately. How fast it actually reaches the tap still depends on your setup, and the cold water sandwich described under the cons can interfere.
Environmentally friendly
A tank loses heat around the clock just keeping its water hot, even when nobody is using it. These standby losses disappear with a tankless unit. Less wasted energy means a smaller carbon footprint, which matters if lowering your household's environmental impact is part of the reason you are shopping for a new heater.
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Cons
The drawbacks are mostly about money and capacity, and they weigh more heavily in some households than in others.
High upfront costs
Expect to pay more at the start. Both the unit and its installation usually cost more than a conventional tank heater. The energy savings may earn that money back over the years, but the price at purchase is enough to put some homeowners off, and how long the payback takes depends heavily on how much hot water you use.
Flow rate limitations
A tankless unit can only heat so much water per minute. In colder climates, where the incoming water starts out colder, or in homes where several hot taps run at once, the flow can fall short and the temperature may fluctuate. Larger households sometimes solve this by installing more than one unit.
Extra costs beyond the unit
The price of the heater is rarely the whole bill. Your home's gas lines, venting, or electrical system may need modifications before it can go in. After that comes maintenance: descaling, often once a year, to keep the system performing well and help it reach the long lifespan it is known for.
Cold water sandwich
Some users notice what is called the cold water sandwich. When the tap first opens, a short burst of cold water comes through before the unit has fully heated the flow. Not every installation has this problem, but where it happens it is an annoyance you live with every day.
Sensitivity to water quality
Tankless heaters tend to be more sensitive to water quality than tanks. Mineral buildup and sediment can damage the unit, so depending on your water supply you may need a filter or some form of water treatment. That adds to both the maintenance work and the running costs.
Limited output capacity
The supply never runs out, but that is different from serving every tap at once. In large households with high simultaneous demand, a single unit may struggle, and water pressure and flow can drop during peak hours, which is exactly when everyone notices.
Complex installation
Fitting a tankless heater is usually a bigger job than swapping one tank for another. Existing gas lines or electrical systems may need adjusting, which generally calls for a professional installer. That labor makes up a noticeable part of the total cost.
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Conclusion
Your hot water habits will probably decide this. A household that rarely runs several hot taps at once, has reasonably soft water, and plans to stay long enough for the energy savings to cover the higher price is a good candidate. If your peak demand is high, or your gas lines or wiring would need major work, get an installer's quote for the full job before comparing it with a new tank.
What do you think?
Do you think the pros outweigh the cons?