LIGHTING AND APPLIANCES: Water Heating
Questions:
What should I look for when buying
a new water heater?
In general, about 20 percent of the energy consumed by an average home is
for water heating. Water heaters have improved significantly in the last 12
years and are much more energy efficient, primarily due to more efficient
combustion for gas models and added insulation.
Because the average life expectancy of a water heater is about
13 years, it is important to consider purchasing one that is energy efficient
since energy-efficient models mean reduced energy consumption, which results
in lower energy costs.
Most water heaters and other home appliances come with a large
yellow sticker called the ENERGYGUIDE. This sticker compares average yearly
energy operating costs for different models, telling consumers which ones
are expected to cost the least during their lifetimes.
Also, most water heaters come with an Energy Factor (EF) value,
which is listed on a separate tag beside the ENERGYGUIDE. The EF is a decimal
value between 0.4 and 1.0 and is the amount of energy supplied to the heated
water, divided by the water heater's total energy consumption. Gas water heaters
have EF values between 0.5 and 0.7, while electric ones range from 0.75 to
0.95. Minimum EF values range from 0.51 to 0.56 for gas units, depending upon
the size of storage tank, to an average of 0.89 for electric ones. Recommended
EF values are 0.61 for gas units and 0.92 for electric water heaters.
All type of water heating units with higher EF values generally
cost more initially, but because of the higher EF value, will more than makeup
for this higher initial cost in yearly energy savings throughout the lifetime
of the water heater.
How do you select the proper size for a water heater?
The size or capacity of water heater needed is based on the maximum amount
of hot water consumed during any one-hour period. This is called the peak-hour
demand.
To determine the peak usage hour for a family, list all the water consuming
activities during that period.
Typical hot water consumption in gallons per usage for various activities
is as follows: shower, 20; bath, 20; shaving, 2; hands and face washing, 4;
hair shampooing, 4; hand dishwashing, 4; automatic dishwasher, 14; food preparation,
5; automatic clothes washer, 32.
The peak for one family might occur in the morning and consist of three showers
(20 gallons each, 60 gallons total), hands and face washing (5 gallons), shaving
(2 gallons), and food preparation (5 gallons), for a total of 72 gallons.
A water heater can provide more than its storage capacity during the first
hour of operation, because it can also heat the water during this period.
This capacity, the total gallons of hot water the heater provides during this
first hour, is referred to as the first-hour rating.
In the sample above, a water heater with a first-hour rating of at least 72
gallons would be required.
Residential water heaters are most commonly available in 20, 30, 40, and 50-gallon
capacities with first hour-ratings ranging from 22 to 100 gallons. Gas and
propane water heaters typically have higher first-hour ratings than electric
heaters of the same storage capacity.
How can I reduce my water heating
costs?
Several simple things can be done to decrease the amount of energy used to
heat water in a home. Water heaters consume about 20 percent of the energy
an average home uses, with more than one-third used in showering and 25 percent
to wash clothes.
Implementing certain energy-efficient measures, even small ones, can make
a noticeable difference in the heating bill.
For example, water heater temperatures should be set to about 120 degrees
and definitely no more than 130 degrees. In general, a 10-degree reduction
in water temperature has been shown to provide an eight percent water-heating
energy savings.
Another important and effective energy-saving measure is to wrap the water
storage tank with an R-12 insulation blanket, especially if the water heater
is an older model. Consult the manufacturer's equipment guide to make sure
an insulation wrap is recommended; it may not be on some newer models. Also,
insulate all exposed hot water pipes with either foam or fiberglass wrap.
Installing low-flow showerheads has been shown to save not only money in reduced
water usage, but also to save energy as well.
Finally, when the time comes to purchase a new clothes washer, selecting one
that is energy efficient will also save on water heating costs.
These energy-saving tips cost very little and have the potential
to not only lower the amount of energy used to heat water in a home, but also
save money as well.
What can you tell me about tankless
water heaters?
Tankless, or demand, water heaters don't have storage tanks, so they heat
water as it is used, on a demand basis.
Because there isn't a storage tank, this type of water heater can save from
10 to 20 percent on the cost of heating water.
A family of four uses about 100 gallons of hot water a day. During the course
of a year, the cost to heat this amount of water will vary from $90 to $700,
depending on the price of energy. If fuel prices are high, the savings gained
from a tankless water heater will be significant. Tankless heaters are available
in either point-of-use or central styles.
Point-of-use heaters are installed near each area that requires hot water.
This minimizes plumbing for new construction. The other type, a central tankless
heater, supplies water for the entire house. Tankless water heaters generally
cost $200 to $500 more than conventional water heaters. While this may seem
like a large premium to pay, the fuel savings may justify the additional cost
during the course of just a few years.
What should I do to keep my water
heater operating at maximum efficiency?
As with any heating or cooling device, regular maintenance of water heaters
goes hand-in-hand with efficiency and safety. Follow these three steps to
assure the water heater is giving maximum efficiency for minimum dollars.
1. Every two months, connect a hose to the bottom drain. Open the valve all
the way, letting the water flush through. Be careful: this is hot water! This
removes sediment, which reduces heating efficiency.
2. Place a bucket under the temperature and pressure (T-P) relief valve discharge,
located on the top or side of the heater. Carefully lift the lever -- again,
the water surging out will be hot. The T-P valve is a safety valve designed
to prevent the tank from exceeding safe temperature and pressure levels. This
test assures that sediment is not blocking the T-P valve.
3. If the unit is gas or electricity, annually inspect the heater's burner
area, checking for dirt or water. If the area is dirty, shut off the pilot
and clean the burner with a shop vacuum. Remember to light the pilot again.
If there are signs of leaks, the water heater will probably have to be replaced,
soon
If the water heater is more than and the bottom drain and T-P valve have never
been checked, they may not seal properly once opened. Replace either valve
if they do not seal tight after operation.
Should I use a water heater insulation
blanket with my new water heater?
Residential water heaters must all meet minimum efficiency standards. For
example, a 40-gallon, gas water heater must have an energy factor (EF) of
at least 0.54, while an electric water heater must have an EF of at least
0.89.
While this is a considerable improvement compared to heaters marketed just
a few years ago, there are water heaters on the market with EF ratings in
the mid-60s or higher for gas and the mid-90s for electric.
If the existing water heater is on the low end of the efficiency rating, then
it is still possible to reduce fuel cost effectively by adding an insulation
blanket. However, if the water heater is on the high end of the efficiency
range, then additional insulation will probably not be of much benefit.
Can you vent a water heater toan
old masonry chimney?
The National Fire Code does not specifically prohibit the use of masonry chimneys
with modern gas appliances. However, it requires the chimney to be lined with
an approved material.
Many old masonry chimneys are not lined. Venting gas appliances into unlined
chimneys could cause drafting problems for the appliance, as well as deterioration
of the masonry.
It is recommended that gas appliances are vented with a properly sized and
designed chimney. Check with local building code officials for their specific
requirements.
