Tank vs. tankless water heating — what's the right choice?
There are many applications where tankless technology is a logical choice.
When helping homeowners choose between tank-type and tankless water heaters for a specific application, it’s advisable to get an impartial recommendation from a manufacturer that offers both technologies. There are still plenty of jobs where tank technology is a good fit, but there’s a growing number of applications where tankless is the smarter choice.
Let’s take an in-depth look at the pros and cons of both water heating technologies.
TANK TECHNOLOGY: THE TRADITIONAL WORKHORSE
For many years, most residential water heating has been the work of the traditional 50-gallon atmospheric-vent, tank-type unit. A gas-fired tank water heater uses about five times less gas than a tankless model (roughly 40,000 Btu/h compared to potentially 200,000 Btu/h). Replacing an old tank water heater with a new tank-type unit is painless because the gas or electric requirements are almost identical.
Tank water heaters are less expensive than tankless models, and they cost less to install and maintain. For example, the impact of hard water and scale buildup in a tank water heater is minimal compared to a tankless model.
Even though they require fewer Btu/h to operate, tank water heaters usually have higher operating costs because they heat, then reheat water to a preset temperature — regardless of your hot water demand.
Sticking with tank technology is often the best choice for older homes that would incur significant costs for upgrading either their gas or electric supply to support tankless. Tank water heaters are good for homes where the occupants seldom run out of hot water (e.g., couples without children).
In addition, tank models can supply much more than the 3 to 5 gpm that tankless units typically provide. Restaurants and many other commercial applications have long favored tank water heaters because they can provide 50 gallons or more of hot water during peak demand.
TANKLESS TECHNOLOGY: THE ENERGY-EFFICIENT ALTERNATIVE
According to the U.S. Department of Energy (DOE), homes that use 41 gallons or less of hot water daily can improve energy efficiency up to 34% by switching from tank to tankless water heating.
The initial cost of a tankless water heater is higher than a conventional tank unit, but tankless models typically last longer and reduce monthly energy bills, which helps offset the higher purchase price. The DOE notes while most tank water heaters typically last 10-15 years, most tankless units have a life expectancy of 20 years or more.
Tankless models are sometimes called “demand” water heaters because they supply continuous hot water when needed. They’re ideal for large families where showers, laundry and food preparation are often happening simultaneously. For this reason, it’s particularly important to size the tankless unit for anticipated peak demand. If the water heater is sized for average daily use, the occupants could run out of hot water during periods of high demand.
Because tankless water heaters eliminate the footprint of a storage tank, they let homeowners free up more living space. Most homes require just one tankless unit. In warmer sections of the U.S. — such as Florida, California and southern Texas — builders and contractors now install them outdoors.
Installing tankless water heaters in new homes is easier than retrofitting them for older homes. Electricians are able to plan for their use in new homes, while retrofit jobs may involve upsizing the gas or electric supply. For example, an electric tank water heater requires just a 30-Amp circuit, while a tankless electric might need a 140-Amp circuit.
Tankless water heaters also require regular descaling, but that’s a simple task with anti-scale filters It uses a non-chemical, non-salt substance causing calcium and magnesium in the water to bind together, preventing them from sticking to the water heater. All the service person has to do is replace a cartridge in the filter every two years.
COMMON MISCONCEPTIONS ABOUT TANKLESS
Here are some things you may have heard about tankless technology that would discourage you from installing it, but it’s important to get all the facts.
“Venting is difficult with tankless.” This all depends on the design of the home. It’s true existing venting may not get used, but if the tankless unit is going in a room with an outside wall, venting is easy.
“Increasing gas supply is a big headache.” Once again, it depends on the design of the home. If the tankless water heater is located close to the gas meter, upsizing is simple. The challenges come when the unit is placed a long distance from the meter.
“Tankless doesn’t work well in commercial applications.” Tankless technology would make sense for a hotel or senior care facility where hot water needs are spread evenly across the day — showers in the morning, laundry in the afternoon, etc. Installing multiple tankless units in commercial facilities also provides redundancy. If one tankless unit needs servicing, the other ones can still provide hot water.
Manufacturers who make only tankless products are apt to recommend the technology too broadly. You’ll still find many applications where tank technology is the better choice. But tankless installations are indeed on the rise because of their superior energy efficiency, space savings and continuous supply of hot water on demand.