Feb 17, 2022
The average household spends
$400-$600 annually heating its water, according to Energy.gov. That makes
heating water the second largest expense in your home, accounting for 14-18% of
your utility bills. The average water heater lasts 10-15 years, which makes it
an appliance that will likely be replaced more than once in a homeowner’s time
in a home. The question is, what do you do when it’s time for a replacement?
How do tankless water heaters
A tankless hot water heater, also
known as a demand water heater, is exactly what it sounds like. Unlike
traditional water heaters, where tanks store water and maintain the water’s
temperature until someone turns on the tap or the washing machine, tankless
heaters only heat the water when an actual demand is made. No tap on, no water
One difference between tankless
water heaters vs. regular water heaters is that a tankless will heat the water
directly. If you turn on the shower upstairs, cold water travels through a pipe
to the tankless heater. There, either a gas burner or an electric element heats
the water, delivering a constant supply of hot water for however long that
shower occurs. No concerns about running out of hot water while you wait for
the storage tank to refill with hot water.
You should note this caveat, however, when comparing a tankless vs. traditional water heater: the output of a tankless heater can limit its flow rate. Energy.gov says that tankless water heaters typically provide hot water at a rate of 2-5 gallons a minute, with gas-fired tankless heaters producing a higher flow rate than heaters powered by electricity.
This means that even gas-fired
tankless heaters can have trouble producing enough hot water for someone to
take a shower if, say, the dishwasher also is running. Energy.gov offers a
potential solution for this problem: install multiple tankless water heaters.
Connect them in parallel so that they can meet any simultaneous hot water
needs. Another option is to install separate tankless water heaters for
Comparing tankless water heaters
vs. regular water heaters
Deciding between a tankless vs.
tank hot water heater means taking into account a number of factors.
- Tankless vs. traditional water
heater life expectancy: Regular water heaters typically last 10-15 years. Tankless,
if maintained properly, can last 20 or more.
- Cost of tankless water heaters
vs. regular water heaters: When considering cost of water heaters, you need to consider
up-front and installation costs, as well as potential tankless water
heater energy savings. Tank water heaters typically cost less than
tankless water heaters. When testing tankless vs. tank hot water heaters,
Consumer Reports found gas-fired tankless heaters ranged from $800-$1,150
compared to regular storage tank models in the $300-$480 range.
Additionally, the report noted that tankless gas models had higher
installation costs, thanks to the need for electrical outlets, upgraded
gas pipes and a new ventilation system.
- Potential energy usage of
tankless vs. tank water heaters: When comparing water heaters, it’s important to note that
storage tanks have some standby heat loss; water cools as it’s held in the
storage tank until use. That requires the heater to periodically heat it,
even when it’s not actually being used. In contrast, tankless heaters
don’t have this additional energy spend since no water is heated until
it’s needed. Energy.gov summarizes
the potential tankless water heater energy savings this way:
- Tankless heaters can be 24-34%
more energy-efficient than regular water heaters for households that use
41 gallons or fewer of hot water daily.
- Tankless heaters can be 8-14%
more energy-efficient for households that use around 86 gallons daily.
- Installing a tankless heater
at each hot water outlet, Energy.gov says, can increase tankless water heater
energy savings by up to 27-50%.
- ENERGY STAR estimates that a
typical family can save at least $100 annually in tankless water heater
energy savings by using an ENERGY STAR-certified tankless heater.
How to choose a tankless water
If you’ve decided that tankless
water heater energy savings have made a tankless heater the right route for
your home, the next step is figuring out how to choose a tankless water heater.
Here, as with many other appliances, size matters.
Here are some tips to help you
choose the best heater for your hot water needs.
- Know your water heater flow
heaters are rated by the maximum temperature increase possible at a given
flow rate, Energy.gov says.
- Decide how many hot water
appliances or devices you expect to use at one time. Know the flow rate (water
gallons per minute) for each one. Add those together to know the maximum
flow rate you’ll need.
- Factor in location. Consumer Reports compared
tankless water heaters vs. regular water heaters and found that
groundwater temperatures affect water output in tankless models. In the
test, they discovered that the same model heater produced 7.2 gallons per
minute in a warm Florida garage but only produced 4.2 gallons per minute
in a cold New England basement. That’s because the colder water required
the overall water temperature to be heated by 77 degrees in New England
rather than only 44 degrees in Florida. The report suggests using your
coldest groundwater temperature to calculate the gallons per minute you’ll
need in your heater model when looking at how to choose a tankless water
heater. Energy.gov suggests assuming that the incoming water is 50 degrees
Fahrenheit if the groundwater temperature is unknown. Most uses require
hot water to reach a temperature of 120 degrees Fahrenheit. So, assuming
your groundwater temperature is 50 degrees, that would mean a temperature
rise requirement of 70 degrees.
Bottom line: the lowly water heater does a lot of work each day. Understanding the differences between a tankless vs. tank hot water heater can help you make the best energy choice for your family and needs.