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Geothermal Heat
Pumps Make Sense for Homeowners
Geothermal heat pumps are one of the most
efficient ways to heat and cool a home and provide hot water. More and more
homeowners are discovering the benefits of these systems, which tap the
relatively constant temperature of the Earth a few feet underground, for both
new homes and retrofits in existing houses.
Why a Geothermal Heat Pump?
The installation of a heating or cooling
system is a decision that will affect a homeowner's comfort—and pocketbook—for
years to come. One option to think about is a geothermal heat pump (GHP),
which is one of the most cost-effective and longest-lasting heating and
cooling systems on the market. Plus, GHPs provide free hot water as a
byproduct of air conditioning for the household in the summer.
Also known as ground-source heat pumps
or GeoExchangeSM systems, GHPs provide many benefits to the
homeowner in both new and retrofit situations. Surveys by utilities illustrate
a high level of satisfaction with GHPs compared to conventional systems. In
fact, more than 95% of all GHP users would recommend a similar system to their
friends and family.
According to the Environmental
Protection Agency (EPA), GeoExchange systems are the most energy- efficient,
environmentally clean, and cost-effective space conditioning systems available
(source: "Space Conditioning: The Next Frontier," EPA 430-R-93-004,
April 1993).
Simply put, a GHP system moves the heat
from the earth (or a groundwater source) into the home in the winter, and
pulls the heat from the house and discharges it into the ground in the summer.
The underground (or underwater) piping loops serve as a heat source in the
winter and a heat sink in the summer.
While many parts of the country
experience seasonal temperature extremes—from scorching heat in the summer
to sub-zero cold in the winter—a few feet below the earth's surface the
ground remains at a relatively constant temperature. Depending on latitude,
ground temperatures range from 45°F (7°C) to 75°F (21°C). Like a cave,
this ground temperature is warmer than the air above it during the winter and
cooler than the air in the summer. The GHP takes advantage of this by
exchanging heat with the earth through a ground heat exchanger rather than
with the outside air as with air conditioners.
GHPs Offer Many Benefits
In even the coldest climates, geothermal
heat pumps offer cost savings, durability, low maintenance, year-round
comfort, and other benefits.
Cost Effective
Geothermal heat pumps save money in
operating and maintenance costs. While the initial purchase price of a
residential GHP system is often higher than that of a comparable gas-fired
furnace and central air-conditioning system, it is more efficient, thereby
saving money every month. For further savings, GHPs equipped with a device
called a "desuperheater" can heat the household water. In the summer
cooling period, the heat that is taken from the house is used to heat the
water for free. In the winter, water heating costs are reduced by about half.
On average, a geothermal heat pump
system costs about $2,500 per ton of capacity, or roughly $7,500 for a 3-ton
unit (typical residential size). In comparison, other systems would cost about
$4,000 with air conditioning. When included in the mortgage, the homeowner has
a positive cash flow from the beginning. For example, say that the extra
$3,500 will add $30 per month to each mortgage payment. But the energy cost
savings will easily exceed that added mortgage amount over the course of each
year. On a retrofit, the GHP's high efficiency typically means much lower
utility bills, allowing the investment to be recouped in two to ten years.
In addition, some electric utilities
have financing packages that make the purchase of a GHP system even less
expensive. Other utilities are providing special electric rates for homes with
GHP systems installed
Durability
Because they use fewer mechanical
components, and because those components are sheltered from the elements,
leaves, dirt, and possible vandalism, geothermal heat pumps are durable and
highly reliable. The underground piping used in the system often has 25- to
50-year warranties, and the GHPs themselves typically last 20 years or more.
Low Maintenance
Geothermal heat pump systems have fewer
maintenance requirements than most other systems. When properly installed, the
underground components are virtually worry free. The components in the living
space are easily accessible, which increases the convenience factor and helps
ensure that the upkeep is done on a timely basis.
Year-Round Comfort
Like the typical forced-air furnace or
central air-conditioning system, a GHP system uses ductwork. A two-speed GHP
system is so quiet inside a house that users do not know it is operating
because there are no tell-tale blasts of cold or hot air, depending on whether
it's the heating or cooling season.
GHPs also improve humidity control by
maintaining about 50% relative indoor humidity, making GHPs very effective in
humid areas.
Quiet Operation
With GHPs, there are no outside
condensing units like air conditioners, so there's no concern about A/C noise
near patio areas or decks, or bothering the neighbors with the constant hum of
a conventional air conditioner.
Geothermal Heat Pumps Are Highly
Efficient
A study by the Environmental Protection
Agency (source: "Space Conditioning: The Next Frontier," EPA
430-R-93-004, April 1993) analyzed six locations representing major climate
zones in the U.S. These cities (Burlington, VT; Chicago, IL; upper New York
City; Portland, OR; Atlanta, GA; and Phoenix, AZ) were chosen to compare the
performance and costs of emerging high-efficiency space-conditioning equipment
with equipment already on the market.
For all locations, the findings named
geothermal heat pumps as the most efficient heating and cooling systems over
other types of space-conditioning equipment including high-efficiency gas
furnaces and air conditioners. Geothermal heat pump installations in both new
and existing homes can reduce energy consumption 25% to 75% compared to older
or conventional replacement systems. Annual operating costs were also lowest
with geothermal heat pumps. Add in the benefits of the desuperheater for hot
water savings, and it's easy to see how a GHP system is the most efficient
available.
GHPs Have Low Environmental Impact
Because a GHP system is so efficient, it
uses a lot less energy to maintain comfortable indoor temperatures. This means
that less energy—often created from burning fossil fuels—is needed to
operate a GHP. According to the EPA, geothermal heat pumps can reduce energy
consumption—and corresponding emissions—up to 44% compared to air-source
heat pumps and up to 72% compared to electric resistance heating with standard
air-conditioning equipment.
Financing a GHP System
Many geothermal heat pump systems carry the
DOE and EPA ENERGY STAR® label. ENERGY STAR®-labeled equipment can now be
financed with special ENERGY STAR® loans from banks and other financial
institutions. The goal of the loan program is to make ENERGY STAR® equipment
easier to purchase, so these loans were created with attractive terms. Some
loans have lower interest rates, longer repayment periods, or both. Ask your
contractor about ENERGY STAR® loans or call the EPA's ENERGY STAR® toll-free
hotline at 1-888-STAR-YES for a list of financing options.
Homeowners should also check with their
utility and ask if they offer any rebates or special electric rate programs.
Another way to help finance the purchase of a GHP system is to roll the cost
into an "energy-efficient mortgage" that would cover this and other
energy-saving improvements to the home. The additional cost can be combined
into the mortgage and will produce a positive cash flow. Banks and mortgage
companies can provide more information on these types of loans.
DOE Spreads the Word about GHPs
In 1994, the U. S. Department of Energy
(DOE), working closely with the EPA, Edison Electric Institute, Electric Power
Research Institute, International Ground Source Heat Pump Association (IGSHPA),
National Rural Electric Cooperative Association, and industry, helped to
create the Geothermal Heat Pump Consortium (GHPC). The GHPC launched the
National Earth Comfort Program, designed to foster the development of a
fast-growing, self-sustaining, national GHP industry infrastructure. DOE has
also supported research and development activities, especially through IGSHPA;
the American Society of Heating, Refrigeration, and Air-Conditioning
Engineers; the National Ground Water Association; and DOE's national
laboratories. The work has targeted several areas of GHP technology, lowering
the cost of ground heat exchangers, and developing advanced design software.
In partnership with the GHPC, DOE's
Office of Geothermal Technologies seeks to increase annual installations of
GHP systems to about 400,000 by 2005 and reaching about 2 million installed
(cumulative) that same year. Achieving the goal of 400,000 annual
installations by 2005 will save consumers over $400 million per year in energy
bills and reduce U.S. greenhouse gas emissions by over 1 million metric tons
of carbon each year.
The System for the Future
With their high efficiency and user
satisfaction, geothermal heat pumps are one option homeowners should consider.
Not only will they save energy and money, they'll reduce emissions and provide
indoor comfort at less cost to the environment.
Case Study—Minnesota
Located in the middle of Minnesota—where
temperatures can range from 90°F (32.2°C) with 95% humidity in the summer to
-18°F (-27.8VC) in the winter—Dennis Eichinger's 3,400-square-foot home
averages a little over $44 per month in electricity bills.
The owner has been very satisfied with
the unit's quietness, high quality, reliability, and low maintenance. House
guests also marvel at the comfort level of the house—they don't feel any
drafts, just an even temperature throughout the house.
The five-ton ground source heat
exchanger connects to five horizontal Slinky™ loops, totaling 3,000 feet of
pipe, buried next to the home at a depth of eight feet (2.4 meters).
GHP technology heats and cools as well
as, or better than, conventional systems, even in Minnesota's extreme
temperatures.
Case Study—Florida
Panama City, Florida, homeowner Keith
Swilley partnered with his builder and local electric utility to create a
2,000-square-foot home that's a model of efficiency. It saves so much energy
that the home won the 1997 Energy Value Housing Award for the custom home
category for hot/humid climates at the National Association of Home Builders
Conference in Houston.
Mr. Swilley used energy-efficient
features from ceiling to floor, with cellulose insulation in the walls and
attics, sealed ductwork, and efficient doors, windows, and lighting. However,
the feature that saves the most energy is the GeoExchange system.
The geothermal heat pump heats and cools
the house and provides hot water for the residents with a desuperheater, which
takes waste heat from the air-conditioning process and uses it in the water
heater. The desuperheater actually helps the GeoExchange unit reach heightened
levels of efficiency.
The system was metered separately and
has proven to be a valuable investment, as the home's total energy bill for
1996 was $906. Amazingly, only $253 of the total annual energy bill was used
for heating and cooling the 2,000 square feet of conditioned space. "The
energy bills are even lower than I anticipated," said Mr. Swilley,
"and the comfort level in the winter and summer is much greater than
expected. I never dreamed I could heat and cool my home for 69 cents a
day!"
SIDEBAR
Design and Installation
Installing a geothermal heat pump system
is not a project for the do-it-yourselfer. Because the pipes are underground,
they need to be designed and installed correctly, and properly pressure
tested.
The consumer should insist that a
qualified and experienced contractor, who has received training at a
recognized institution, install the system. For a list of installers and
training locations, contact the International Ground Source Heat Pump
Association and Geothermal Heat Pump Consortium (see For More Information
section).
For More Information
The following organizations serve as
excellent resources for information on geothermal energy and its various
applications.
U.S. Department of Energy (DOE)
Office of Geothermal Technologies, EE-12
1000 Independence Avenue, SW
Washington, DC 20585-0121
(202) 586-5340
http://www.eren.doe.gov/geothermal/
The Energy Efficiency and Renewable Energy
Clearinghouse (EREC)
P.O. Box 3048
Merrifield, VA 22116
(800) DOE-EREC (363-3732)
Fax: (703) 893-0400
E-mail: doe.erec@nciinc.com
http://www.eren.doe.gov/consumerinfo
Geo-Heat Center
Oregon Institute of Technology
3201 Campus Drive
Klamath Falls, OR 97601-8801
(503) 885-1750
http://www.oit.osshe.edu/~geoheat/
Geothermal Heat Pump Consortium, Inc. (GHPC)
701 Pennsylvania Avenue, NW
Washington, DC 20004-2696
(888) ALL-4-GEO (255-4436)
http://www.geoexchange.org/
International Ground Source Heat Pump
Association (IGSHPA)
490 Cordell South
Stillwater, OK 74078-8018
(405) 744-5175
(800) 626-4747
http://www.igshpa.okstate.edu/
U.S. Department of Energy
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Heat Pumps Make Sense for Homeowners
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