Download 5.3 Potential and opportunities for energy efficiency in buildings

5.
Energy efficiency in buildings
5.1
Global view of energy efficiency
At the global scale, energy use and GHG emissions data for residential and commercial sectors can be difficult
to quantify. The amount of energy use attributed to buildings, as a proxy for residential and commercial
sectors, varies by country and climate. Energy consumption levels and primary fuel types are related to other
economic and social indicators, such as national income and level of urbanisation. In general, developed
countries consume more energy per capita than developing countries. Developed countries tend to have
bigger building sizes for comparable purposes, and they tend to use more appliances and other energy-using
equipment than developing countries.
Urban areas in developed countries use less energy per capita than rural areas. This is because of greater
efficiency from a variety of factors, including public transportation and district heating in higher-density areas.
However, the opposite effect can be seen in many developing countries where energy use is higher in cities
than in rural areas because residents often have higher incomes and greater access to energy services.22
Indoor combustion of biomass and coal is a significant health concern; high rates of respiratory illness have
been documented in areas that predominantly use biomass or coal for heating and cooking. Reducing GHG
emissions through appropriate technology advances, energy efficiency improvements, and the use of
alternative fuels therefore may have important health co-benefits.
Commercial energy consumption is currently almost 14 times higher in developed than developing countries;
energy consumption by commercial buildings is projected to be the highest-growing end-use sector for energy
in developing countries.23 Economic growth in developing countries will likely lead to increased demand for
energy and, without efficient products and practices, could lead to substantially higher energy global
consumption and GHG emissions.
The arguments for improved energy efficiency in buildings focus on: reduced energy costs to consumers,
security of energy supply; cheaper option than investing in increased energy capacity; improved comfort;
lower GHG emissions, thus contributing to climate change strategies and helping to achieve the Kyoto Protocol
targets; contribution to the rehabilitation of certain building types. 1 It is a major contribution to the objective
of sustainable development andimproved energy efficiency in buildings is important to the building’s energy
service industries.
Emissions from the residential and commercial sectors, including both direct emissions and end-use electricity
consumption, can largely be traced to energy use in buildings. A variety of diverse factors determine the
amount of energy buildings consume; these range from the size of the building to the design and materials
used to the kinds of lighting and appliances installed.
5.2 Energy use in buildings
The primary end uses of energy vary between the residential and commercial sectors. In the residential sector,
heating, ventilation, and air conditioning (HVAC) account for 39% of total energy use. Since HVAC uses more
than a third of energy use in the residential sector, total energy demand from this sector is fairly sensitive to
weather and varies both by region in a single year, as well as through time in a given location. Other significant
end uses of energy in the residential sector include lighting, water heating, electronics, refrigeration, and
cooking (see Figure 1).
Figure 1: Residential Buildings Total Energy End Use (2006)
Source: DOE, 2008 Buildings Energy Data Book, Section 2.1.5, 2008.
In the commercial sector, HVAC accounts for nearly a third of total energy use and lighting accounts for a
quarter. Electronics, water heating, refrigeration, computers, and cooking also use significant quantities of
energy in the commercial sector (see Figure 2). The commercial sector encompasses a variety of different
building types, including schools, restaurants, hotels, office buildings, banks, and stadiums. These different
building types can have very different energy needs and energy intensities.
Figure 2: Commercial Sector Buildings Energy End Use (2006)
Source: DOE, 2008 Buildings Energy Data Book, Section 3.1.4, 2008.
This pie chart includes an adjustment factor used by the EIA to reconcile two datasets
5.3
Potential and opportunities for energy efficiency in buildings
There are several arguments for improved energy efficiency in buildings (Janssen, 2004) and these include
reduced energy costs to consumers, which for many the reduction is important in avoiding “fuel poverty”
(where energy costs represent a disproportionate and unsustainable share of disposable income); security of
energy supply; cheaper than investing in increased energy capacity; improved comfort; lower GHG emissions,
which means a major contribution to climate change strategies and helping to achieve the Kyoto Protocol
targets; and major contribution to the objective of sustainable development.
5.3.1
Defining energy efficiency potentials
Energy efficiency potential is a concept that needs clarification. Energy efficiency can be measured according
to different criteria, each with different potentials (IEA, 1997).
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Theoretical potential corresponds to an ideal. It refers to the lowest amount of energy needed to
perform a service if all energy losses, frictions and other inefficiencies could be eliminated. The
theoretical potential is difficult to assess and will always remain a remote benchmark.
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Technical potential is where the same service would be provided using the best commercially
available technology available at the time regardless of cost. It is the theoretical maximum amount of
energy use that could be displaced by efficiency, disregarding all non-engineering constraints like
cost-effectiveness and the willingness of end-users to adopt the efficiency measures. It assumes
immediate implementation of all technologically feasible energy saving measures, with additional
efficiency opportunities assumed as they arise from activities such as new construction.
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Economic potential depends on energy costs and how technologies are costed. The economic
potential is achievable in a fair and perfectly functioning market economy, where externalities are
accounted for and prices send the right signal. It refers to the subset of the technical potential that is
economically cost-effective as compared to conventional supply-side energy resources (Mosenthal
and Loiter, 2007). The technical and economic potentials are theoretical numbers that assume
immediate implementation of efficiency measures, with no regard for the gradual ramping up process
of real-life programmes. They both ignore market barriers to ensuring actual implementation of
efficiency and only consider the costs of efficiency measures themselves, ignoring any programmatic
costs (e.g., marketing, analysis, administration) that would be necessary to capture them
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Social potential refers to the saving that can be achieved at a net positive economic effect to society
as a whole. It is higher than the economic potential and is a form of economic potential but seen from
the society's point of view, not the individual's.
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Achievable potential (market/maximum achievable potential) refers to the amount of energy use that
efficiency can realistically be expected to displace (Mosenthal and Loiter, 2007), assuming the most
aggressive programme scenario possible, such as providing end-users with payments for the entire
incremental cost of more efficiency equipment. It takes into account real-world barriers to convincing
end-users to adopt efficiency measures, the non-measure costs of delivering programmes (for
administration, marketing, tracking systems, monitoring and evaluation, etc.), and the capability of
programs and administrators to ramp up program activity over time. Market potential thus refers to
the potential that is expected to be achieved under the “business as usual” case, with all the current
obstacles, institutional and market imperfections, and expected energy prices.
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Program potential is the efficiency potential possible under given specific program funding levels and
designs. They estimate the achievable potential.
5.3.2 Residential and commercial sector mitigation opportunities
Reducing emissions from the residential and commercial sectors can be done in a variety of ways and on a
number of scales:21
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Addressing landfills: Landfill waste can be reduced (thereby lowering the volume of material that
when it decomposes produces methane, a powerful greenhouse gas) or harnessed as an energy
source. Methane-capture systems in landfills prevent GHGs from being released into the atmosphere.
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Reducing embodied energy in building materials: Embodied energy refers to the energy used to
extract, manufacture, transport, install, and dispose of building materials. Emission reductions can be
made by choosing low carbon materials—such as local materials, materials that sequester carbon,
and products manufactured at efficient industrial facilities.
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Improving building design and construction: Using building design and construction techniques to
maximize the use of natural light and ventilation can minimize the need for artificial light and HVAC
equipment. This can be achieved by using appropriate building shading techniques, installing windows
that minimize or maximize solar intake (depending on the region), and insulating properly to prevent
unwanted air flow between indoor and outdoor spaces. Many other options are available, and
“green” builders are constantly creating innovative ways to maximize efficiency in building spaces.
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Increasing end-use energy efficiency: Using efficient appliances can minimize energy consumption
and concomitant GHG emissions from electricity and direct fossil fuel combustion. Appliances can use
25% of a home's energy24, and by choosing the right appliance for to match needs and using it
efficiently money can be saved and energy use reduced.
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Adopting new energy-use habits: Adherence to conservation guidelines and making personal choices
to reduce the use of appliances, artificial lighting, and HVAC equipment (for example, by shutting
them off when they are not in use).
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Heat pump hot water: Heat pump hot water systems use heat from the air to heat water. They use
around one quarter of the electricity of a normal storage hot water system. To further improve the
efficiency of the heat pump you can attach your heat pump hot water system to a solar booster. The
increased efficiency of heat pump systems, where installed in suitable locations, will compensate for
the upfront costs. When installed in an appropriate location25: the difference in cost will be paid back
over the life of the system as less will be spend on heating water, a heat pump may be the next best
choice for heating hot water if one can't have a solar hot water system, they use electricity efficiently
and can heat water day and night, they usually have a smaller storage tank than solar hot water
systems, and reduce the amount of greenhouse gases a home produces.
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Heating and cooling: Heating and cooling needs can be reduced by using passive design. Passive
design helps maintain the interior temperature of a home all year round with little mechanical
heating and cooling. Passive design ideas include: insulating the ceiling, walls and floor, sealing
draughts around doors and windows, allowing winter sun to warm the house, stopping summer sun
from entering the house and using natural airflow to help with cross-ventilation.
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Insulation: A well insulated building can reduce heating and cooling bills as insulation acts as a barrier
to heat loss and heat gain, particularly in ceilings, roofs, walls and floors. Insulation helps to reduce
the need to use mechanical heating and cooling systems, saving money on energy bills, improve
weatherproofing and reduce moisture problems like condensation. Home's design, orientation to
north and materials are also factors.
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Renewable energy: Renewable energy is generated from the sun, wind and water. Switching to
renewable energy reduces your environmental impact.
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Renewable Energy Certificates (RECs): If such a system exists in your country you can use them to
reduce the cost of the system or trade them. One could be eligible to receive Renewable Energy
Certificates (RECs) if you install one of the following small-scale energy systems at home25: a solar
power (or PV) system , a wind power (turbine) system, a hydro (water) power system , a solar hot
water system , and a heat pump hot water system
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Solar hot water: Solar hot water systems use the sun to heat water. The benefits of solar hot water far
outweigh the upfront cost as the difference in cost will be paid back quickly, as less is spent on
heating water, and results in reduction in the amount of greenhouse gases produced.
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Solar power: Solar power systems use photovoltaic panels to convert sunlight into energy. A PV
system can connect to the mains electricity grid or be a stand-alone system. If connected to the grid,
you may be able to sell your excess energy to your electricity retailer. The benefits of solar power
outweigh the upfront cost as solar power reduces the need to burn fossil fuels; is generated without
creating greenhouse gases; is a quiet and non-polluting power source that can reduce your
environmental impact and PV panels have no moving parts, need little maintenance and have a life
span of 20 years or more.
5.3.3 Energy efficiency technologies and measures in buildings
A wide range of tested and commercially available technologies exist and these can substantially reduce
energy use and provide environmental benefits.26 For example in the European Union, where buildings
account for more than 40% of all CO2 emissions, a range of measures such as switching to energy efficient light
bulbs, appliances and boilers or improving insulation, could significantly reduce energy use and the resulting
CO2 emissions.27 Below is outline of energy efficient technologies and measures that are variously employed to
reduce energy consumption and create low carbon environments:
1. Structural insulated panels
Structural insulated panels (SIPs) are high performance building panels used in floors, walls, and roofs for
residential and light commercial buildings. The panels are typically made by sandwiching a core of rigid foam
plastic insulation between two structural skins of oriented strand board (OSB). SIPs are manufactured under
factory controlled conditions and can be custom designed for each home resulting in a building system that is
extremely strong, energy efficient and cost effective. Building with SIPs generally costs about the same as
building with wood frame construction, when one factors in the labour savings resulting from shorter
construction time and less job-site waste.5 Other savings are realised because less expensive heating and
cooling systems are required with SIP construction. They provide superior and uniform insulation compared to
more traditional construction methods offering energy savings of 12% to 14%, and have high R-values as well
as high strength-to-weight ratios.6 The most common types of SIPs use insulation made from expanded
polystyrene or polyisocyanurate, a polyurethane derivative.
2. Insulated concrete forms
Insulating concrete forms (ICFs) are rigid plastic foam forms that hold concrete in place during curing and
remain in place afterwards to serve as thermal insulation for concrete walls. The foam sections are lightweight
and result in energy-efficient, durable construction. The three basic form types are hollow foam blocks, foam
planks held together with plastic ties, and panels with integral foam or plastic ties. They provide backing for
interior and exterior finishes. Insulation values of ICF walls vary depending on the material and its thickness.
Typical insulation values range from R-17 to R-26, compared to between R-13 and R-19 for most wood-framed
walls.7 Reinforced concrete walls and foundations offer structural, energy-saving and cost-saving advantages
over traditional stick-frame construction and standard insulation methods. ICF construction provides for more
efficient construction, structural stability and a healthier living environment while reducing energy
consumption:
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30% lower construction cost
50% less construction time
Multi-dimensional building product
Better moisture & mould control
More manageable air quality
Greater wind sheer seismic and stability
Greater comfort & lower energy (8)
3. Geothermal heat pumps
Ground source heat pumps are usually used to heat water for radiators, under-floor heating systems and hot
water. Beneath the surface, the ground stays at a constant temperature, so a ground source heat pump can
be used throughout the year - even in the middle of winter. A ground source heat pump circulates a mixture of
water and antifreeze around a loop of pipe – called a ground loop – which is buried in the ground. Heat from
the ground is absorbed into this fluid and is pumped through a heat exchanger in the heat pump. Low grade
heat is then extracted by the refrigeration system and, after passing through the heat pump compressor, is
concentrated into a higher temperature useful heat capable of heating water for the heating and hot water
circuits of the house. Ground loop fluid (now cooler) passes back into the ground where it absorbs more
energy from the ground in a continuous process. Heat pumps have some impact on the environment as they
need electricity to run, but the heat they extract from the ground, air, or water is constantly being renewed
naturally. The efficiency of a ground source heat pump is measured by a coefficient of performance (CoP) - the
amount of heat it produces compared to the amount of electricity needed to run it. A typical CoP for a ground
source heat pump is around 3.2 if used with under floor heating (it can be reduced if used with radiators). This
means for every unit of electricity used to power the pump, 3.2 units of heat is received. Heat pumps reduce
CO2 emissions: on average a ground source heat pump could save around 540kg of carbon dioxide every year
when replacing an oil boiler. Emissions can be reduced further if the heat pump is partly powered by another
renewable technology, such as solar electricity (PV) or some other form of renewable electricity generating
system to partly power the compressor and pump. Or consider using solar hot water to provide low carbon hot
water in the summer months. Other advantages include; no requirement of fuel deliveries, provides provide
space heating and hot water, can lower fuel bills, depending on what heating fuel is being replaced, and it is a
‘fit and forget’ technology because it needs little maintenance.9
When geothermal heat pump systems are installed in commercial buildings, the state-of-the-art designs are
extremely competitive on upfront costs when compared with cooling towers and boilers, and they have lower
energy and maintenance costs. In addition to their cost effectiveness, geothermal heat pump systems offer
aesthetic advantages, quiet operation, free or reduced-cost hot water, improved comfort among other
benefits.
4. Heat recovery ventilation
Heat recovery ventilation (also known as HRV, mechanical ventilation heat recovery or MVHR) is an energy
recovery ventilator, using equipment known as a heat recovery ventilator, heat exchanger, air exchanger or
air-to-air exchanger, that employ a counter-flow heat exchanger between the inbound and outbound air flow.
HRV provide fresh air and improved climate control, while also saving energy by reducing the heating (or
cooling) requirements. Energy recovery ventilators (ERVs) are closely related and transfer the humidity level of
the exhaust air to the intake air. ERVs can transfer both sensible heat and latent heat and can be considered
total enthalpic devices since both temperature and moisture is transferred, while HRVs only exchange sensible
heat. The benefits include improved building efficiency, fresh air, and better climate control and energy
efficiency.
HRVs and ERVs can be stand-alone devices that operate independently, or they can be built-in, or added to
existing HVAC systems.10
5. Radiant floor heating
Concrete is an ideal carrier of radiant heat because of its inherent thermal mass. As warm water circulates
through the tubing (or as electricity warms the heating elements), the concrete flooring turns into an efficient,
inconspicuous radiator. Typically, radiant heating systems warm floors to temperatures of 75°F to 80°F. The
warm surface then slowly radiates heat upward into the living space, rather than blowing around the heated
air. This natural heat transfer is both more comfortable and energy efficient.
For concrete floor radiant heating systems, the warm-water tubing or electric heating elements can either be
embedded within the slab-on-grade (anywhere from the bottom of the slab to within two inches of the
surface, depending on the design and installation technique) or fastened to the top of a concrete subfloor and
then covered with an overlay. Radiant heating can also be installed in thin concrete slabs placed over plywood,
with a layer of decorative concrete placed on top.18
6. Energy-efficient windows
One way of can decreasing energy usage, saving money, and helping the environment all at the same time in
buildings is to install energy-efficient windows. Windows provide less resistance to heat flow than walls,
ceilings, and floors and can account for as much as 25-30% of the heat loss in residential and commercial
buildings increasing energy use and costs, and decreasing comfort. 11 Performance of windows, walls, ceilings,
and other building components determine the monthly energy cost as well as the required size of your heating
and cooling equipment. The installation of energy- efficient windows reduces monthly energy use (and costs)
and also means that a smaller, less expensive furnace and air-conditioning system will be required. While the
initial cost of energy-efficient windows is high, the monthly savings on energy bills coupled with a reduction in
the purchase price of the heating and cooling system, can more than offset the higher initial cost.11
7. Daylighting
Daylighting is the practice of placing windows or other openings and reflective surfaces so that during the day
natural light provides effective internal lighting. Particular attention is given to daylighting while designing a
building when the aim is to maximize visual comfort or to reduce energy use. Energy savings can be achieved
either from the reduced use of artificial (electric) lighting or from passive solar heating or cooling. Artificial
lighting energy use can be reduced by simply installing fewer electric lights because daylight is present, or by
dimming/switching electric lights automatically in response to the presence of daylight, a process known as
daylight harvesting.12
8. Solar home design and orientation
Building orientation is an important aspect of energy efficient design and correct orientation can make a
significant difference to the liveability and the energy costs associated with heating and cooling Variations in
climate types will obviously have a significant variation on the design parameters. A sustainable house design
for a tropical climate will not generate the same efficiencies in a temperate climate.
9. House orientation
The fundamental principles behind any sustainable design are to use the natural heat of the sun and cooler
temperatures of the evening to maintain a high standard of liveability. Correct design should minimize and in
many cases eliminate the need for mechanized heating and cooling systems. Buildings should complement the
natural light, heating and cooling influences, of the sun, breezes and vegetation. The ideal orientation is the
longest axis of your home and living areas should run east to with the north face having exposure to the sun
when required and shading options when the heating is not required. Tropical homes require shade structures
on all sides for maximum benefit. 13
Window location and design is critical to the success of the how a building will be heated and cooled. The use
of louvers either horizontal or vertical in orientation or casement windows is generally superior to sliding
windows as it provides residents with greater opportunities to control air circulation through the home.
Correctly orientated shade structures ensure that the hot summer sunshine is kept out whilst facilitating the
access of the winter sun.
10. Material selection and insulation
Material selection is very important to consider dense materials are preferable in more temperate climates as
they are able to release heat, whilst lighter materials are characteristically quicker to cool and subsequently
are preferable in tropical conditions. Materials selection should consider the all of life cycle cost of the
material. The combination of insulation with the material selection will provide significant benefits to the
comfort of the building. Generally the selection of insulation should involve a combination of both reflective
and bulk types of insulation.13
Ceiling and wall insulation can improve energy efficiency in buildings. Insulation helps to increase comfort
levels by keeping building warmer in winter and cooler in summer; reduce the amount of energy required for
heating and cooling, saving money on heating and cooling bills and reducing greenhouse gas emission. The
effectiveness of insulation is rated using the thermal resistance value, or R–value. The higher the R–value, the
more effective the product is at reducing heat flow into or out of a home. High ceilings provide for improved
ventilation and the safe use of ceiling fans. Fans are a more energy efficient form of cooling than air
conditioners – the average air conditioner uses more energy than 12 ceiling fans. The size and placement of
windows is a very important consideration when designing your home. Windows can let in too much heat in
summer and also allow significant heat loss in winter.13
11. Thermal mass
Thermal mass refers to the ability of building materials to store heat (thermal storage capacity). The basic
characteristic of materials with thermal mass is their ability to absorb heat, store it, and at a later time release
it. Addition of thermal mass within the insulated building envelope reduce the extremes in temperature
experienced inside the building resulting in the average internal temperature being moderate year-round. The
use of heavyweight construction materials with high thermal mass (concrete slab on ground and insulated
brick cavity walls) can reduce total heating and cooling energy requirements by up to 25% compared to a
home built of lightweight construction materials with a low thermal mass (brick veneer with timber floor). In
general, the greater the daily temperature range, the more thermal mass required. Thermal mass is less
important, but still beneficial, in climates with lower summer temperatures. However, in situations where
solar access is poor, thermal mass could increase winter heating requirements.14
Thermal mass types are traditional which includes water, rock, earth, brick, concrete, fibrous cement, caliche,
and ceramic tile, and Phase change materials (PCM) which stores energy while maintaining constant
temperatures, using chemical bonds to store and release latent heat. PCM’s include solid-liquid Glauber’s salt,
paraffin wax, and the newer solid-solid linear crystalline alkyl hydrocarbons (K-18: 77°F phase transformation
temperature). PCM’s can store five to fourteen times more heat per unit volume than traditional materials.
(Source: US Department of Energy).15
During summer, thermal mass absorbs heat that enters the building. In hot weather, it has a lower initial
temperature than the surrounding air and acts as a heat sink. By absorbing heat from the atmosphere the
internal air temperature is lowered during the day, with the result that comfort is improved without the need
for supplementary cooling. At the night, the heat is slowly released to passing cool breezes (natural
ventilation), or extracted by exhaust fans, or is released back into the room itself. Inside temperatures at night
time will be slightly higher than if there was low thermal mass, however with the cooling night effects,
temperatures are still within the comfort zone (unless a long spell of consistently hot days and nights is
experienced).17
During winter, thermal mass in the floor or walls absorbs radiant heat from the sun through north, east and
west-facing windows. At the night, the heat is gradually released back into the room as the air temperature
drops. A comfortable temperature is thus maintained for some time, reducing the need for supplementary
heating during the early evening. For good winter performance, thermal mass should be exposed to direct
sunlight and is best located in areas with unobstructed north-facing windows. An additional benefit is that
some of the heat from lengthy periods of internal space heating can be stored in the thermal mass. Long after
the heating is turned off, the slow release of heat from the walls or floor will maintain comfortable internal
temperatures.16
12. Efficient lighting and appliances: no cost and low cost measures
Energy efficient lighting delivers high quality long-life performance with energy and cost saving benefits. The
measures include:
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Turn off lights and fans in unoccupied areas and open blinds and shades to allow natural lighting
during the day. Use task or desktop lamps with Compact Fluorescent Light bulbs (CFL) instead of
overhead lights.
Unplug unnecessary electronics and other equipment when not in use. When their energy
consumption is added together, these small items can use as much power as your refrigerator.
Suggestion: use a power strip to make it easier to turn electronics on and off.
Check the temperatures of your refrigerator (38°F to 42°F) and freezer (0°F to 5°F) and clean the coils
annually. If the refrigerator or freezer is just 10° colder than necessary your energy consumption
could be 25% higher.
Use smaller or lower-energy appliances when possible. A larger cooking appliance will use more
energy than a smaller one. Also match the pan size to the element or burner size. A six-inch pan on an
eight-inch burner wastes more than 40 percent of the heat produced by the burner or element.
Wash only full loads and use the air-dry feature on your dishwasher. This can save 15 percent or more
on the energy your dishwasher uses.
Use one bulb instead of multiple bulbs in a multi-bulb fixture whenever possible. A single 100-watt
bulb produces the same amount of light as two 60-watt bulbs and uses 20% less energy. Remember
not to exceed the wattage of the light socket.
Clean bulbs and lampshades regularly to get all the light you’re paying for.
Check the condition of your appliances, especially the refrigerator. Check that the refrigerator door is
sealed tightly by trying to pull a dollar bill out of the closed door. If it removes easily then the gasket
needs to be replaced.
Replace incandescent bulbs with CFLs. CFLs can cost several times more but last 10 times longer and
use 75% less energy
Replace halogen lamps with compact fluorescent torches. The newer bulbs produce less heat and
reduce energy costs by 60 to 80%.
Replace your night light with a 4-watt mini-fluorescent, or 1-watt Light Emitting Diode (LED) night
light.