Heating
water accounts for up to 30 percent of the average home's energy
budget. Some makers of gas-fired tankless water heaters claim their
products can cut your energy costs up to half over regular storage
heaters. So is it time to switch?
Probably
not. Gas tankless water heaters, which use high-powered burners to
quickly heat water as it runs through a heat exchanger, were 22 percent
more energy efficient on average than the gas-fired storage-tank models
in our tests. That translates into a savings of around $70 to $80 per
year, based on 2008 national energy costs. But because they cost much
more than storage water heaters, it can take up to 22 years to break
even—longer than the 20-year life of many models. Moreover, our online
poll of 1,200 readers revealed wide variations in installation costs,
energy savings, and satisfaction.
With
the help of an outside lab, we pitted Takagi and Noritz gas-fired
tankless water heaters against three storage water heaters. We didn't
test electric tankless heaters because many can't deliver hot water
fast enough to replace a conventional water heater if groundÂwater is
cold. Even in areas with warm groundwater, most homeowners would need
to upgrade their electrical service to power a whole-house tankless
model.
Our
tests simulated daily use of 76 to 78 gallons of hot water. That's the
equivalent of taking three showers, washing one launÂdry load, running
the dishwasher once (six cycles), and turning on the faucet nine times,
for a total of 19 draws. While that's considered heavy use compared
with the standard Department of Energy test, we think it more
accurately represents an average family's habits. We also ran more than
45,000 gallons of very hard water through a tanked model and a Rinnai
tankless model to simulate about 11 years of regular use.
Here's what else we found:
Water runs hot and cold
Manufacturers
of tankless water heaters are fond of touting their products' ability
to provide an endless amount of hot water. But inconsistent water
temperatures were a common complaint among our poll respondents. When
you turn on the faucet, tankless models feed in some cold water to
gauge how big a temperature rise is needed. If there's cool water
lingering in your pipes, you'll receive a momentary "cold-water
sandwich" between the old and new hot water. And a tankless water
heater's burner might not ignite when you try to get just a trickle of
hot water for, say, shaving.
Nor
do tankless water heaters deliver hot water instantaneously. It takes
time to heat the water to the target temperature, and just like storage
water heaters, any cold water in the pipes needs to be pushed out. And
tankless models' electric controls mean you'll also lose hot water
during a power outage.
Up-front costs are high
The
tankless water heaters we tested cost $800 to $1,150, compared with
$300 to $480 for the regular storage-tank types. Tankless models need
electrical outlets for their fan and electronics, upgraded gas pipes,
and a new ventilation system. That can bring average installation costs
to $1,200, compared with $300 for storage-tank models.
Tankless units might need more care
During
our long-term testing, an indicator on the tankless model warned of
scale buildup. We paid $334 for special valves and a plumber to flush
out the water heater with vinegar. Many industry pros recommend that
tankless models be serviced once a year by a qualified technician.
Calcium buildup can decrease efficiency, restrict water flow, and
damage tankless models. Experts suggest installing a water softener if
your water hardness is above 11 grains per gallon. Ignoring this advice
can shorten your warranty.
Efficient storage models are pricey
We
also tested the $1,400 Vertex, a high-efficiency storage water heater
by A.O. Smith. The manufacturer claims its installation costs are
similar to a regular storage model. But its high cost offsets much of
the roughly $70 per year the Vertex will save you. Instead, we
recommend buying a conventional storage water heater with a 9- or
12-year warranty. In previous tests, we found that those models
generally had thicker insulation, bigger burners or larger heating
elements, and better corrosion-fighting metal rods called anodes.
Posted: September 2008 — Consumer Reports Magazine issue: October 2008