Energy Efficiency, Principles of Consumption, and Conservation

A blower-door test.

Transportation efficiency
Calculating home energy
Lighting efficiency
Heating and Cooling



When trying to lower your energy use, a good place to start is getting a picture of the many ways you use energy now.




An average American uses more than four times as much energy per year than the global average, 308 million British thermal units (Btu) annually, compared to 73 million Btu per person per year globally,according to recent U.S. government estimates. That guess doesn’t account for foreigners’ use of gathered fuels like wood or manure. However, it also doesn’t include the foreign energy used to source, assemble, and ship an endless profusion of products to the United States from other countries, like China.

The most straightforward uses that you can measure and control are probably in the home and through transportation. Every year, the average car in the United States is driven 12,300 miles and consumes about 67.8 million Btu worth of fuel. On average, Americans use more energy in homes than for transport.  The average household uses less (around 41 million Btu worth of electricity). However, to use electricity at home, we have to generate an additional 90 million Btu of primary energy at the power plant, according to the U.S. Energy Information Administration. What is a Btu?



Untangling the individual’s footprint comes with unrelenting complexities. Perhaps you live in an apartment in a big city and commute to work on the train, plug in your phone and computer at work, eat out every day, shower at a gym, and only come home to sleep. Maybe you travel for work, and your employer pays the expenses. You may pay almost nothing for energy directly. Yet, you are participating in energy use through your work, transportation, food, clothes, water, air travel, and electronic devices.

It’s also difficult to calculate how much energy is used up in buying new things. If you replace your car every two years, or you have a large home that you’re constantly remodeling, chances are your true energy footprint is much larger than you will be able to calculate.

The good news is you can calculate some aspects of your energy use and reduce it. And even if you plug in at work, it’s quite possible to make a decent ballpark estimate of how much energy that takes, too.



As a driving culture with access to cheap fuels — relative to our incomes — Americans use a lot of energy getting around. Transportation of goods and people accounted for almost a third of greenhouse gas emissions in 2009, according to the U.S. Energy Information Administration.

Reducing energy use in transportation is guaranteed by replacing car, truck, or motorcycle trips with biking or walking. For a normal healthy adult, walking a mile or two daily should be well within reach. Biking is a faster option, but it’s often considered a child’s transportation method in the United States. In countries like the Netherlands, it’s ordinary to see anyone on a bike, from babies in handlebar seats to well-groomed professionals.

Nonetheless, social customs, transportation infrastructure, suburban development, weather, and promotion of driving over other forms of transportation make it inconvenient and sometimes impossible to change Americans’ driving habits, at least without changing jobs or moving to a new city. A 2005 ABC News/Time magazine/Washington Post poll found that only 4 percent of 1,203 Americans used public transportation to get to work.

Even if driving is a must, driving efficiency can be improved. More efficient vehicles are available, like hybrids and some electric vehicles. Fuel economy can be improved by better car design and better driving. There’s also car-sharing and carpooling.

Analyzing, grouping, and prioritizing destinations can cut down on unnecessary trips. Yes, getting to work is mandatory perhaps, but a whopping 85 percent of car trips are for shopping, errands, and social or recreational reasons, according to a 2001-2002 government survey.

Other alternatives include public transit, ridesharing, and smaller transportation modes like skateboards, scooters, Segways and even electric bikes.

In China, the low-speed electric bicycle is extremely popular and far more efficient than driving or even taking the bus. It’s a regular pedal bike with a rechargeable battery that boosts the pedaler’s power but doesn’t travel faster than about 12.4 miles per hour. Somewhat heavier than standard bikes, electric bikes can still be pedaled without power on the flat or downhill, and the battery can help the rider stay sweat-free and comfortable on the uphill climb.



Estimating home energy use is getting easier now that utilities have installed smart meters that display electricity demand moment-to-moment. Depending on the utility that supplies your power, if you have a smart meter, you may already be able to log in online and track your hour-by-hour power use on any particular day, compare weekdays to weekends, or see if the house-sitter blasted the air conditioning. You can see how much electricity your home draws right now, and you can turn on and off appliances to see how each one contributes.

If you don’t have a smart meter, to calculate the energy that individual items in your home use, you need to look up how many watts each device — televisions, refrigerators, computers, routers, lights, electric air and water heaters — uses. That nameplate wattage is usually printed on the device.

Some sample nameplate wattages (watts):

Clock radio: 10
Coffeemaker: 10
Dishwasher: 1200-2400
Ceiling fan: 65-175
Space heater: 750-1500
Computer: 200-300 (awake), 20-60 asleep
Laptop: 50
Refrigerator: 725

Weekly energy per device = wattage x hours it’s “ON” per week

For devices that cycle on and off, like refrigerators and air conditioners, you’ll divide the resulting number by three.

You’ll also want to examine how much natural gas, propane, or other fuels you use for heating and cooling space, heating water, and cooking. While electric devices tend to be more efficient than gas-powered devices in your home, electric devices actually tend to use more energy overall because of loss of efficiency when the electricity was generated and transmitted to your home.

If you’re in the market for replacing you refrigerator or other appliance, and want to find out more about efficient options, a good resource for information is the Energy Star program.

Another detailed resource for tracking your energy-related emissions of greenhouse gas is the Home Energy Saver, built by the U.S. Department of Energy and Lawrence Berkeley Laboratory.

Know that devices don’t precisely use what their nameplate wattage says. Various factors affect how much energy something uses. For example, using the maximum brightness setting on a laptop computer will require more energy. Air conditioners will require much more energy to operate in very hot weather not only because it’s hotter outside but because the refrigerant becomes less efficient as it gets warmer, particularly if the refrigerant gets into the high nineties Fahrenheit. See below for more about heating and cooling.



You can improve your efficiency by replacing appliances and redoing construction, but you can also conserve energy by using less demanding settings, adjusting the thermostat, and turning items like computers and televisions off when they’re unused.



Unlike the days of candles and whale oil lamps, today we have many electrical lighting options. Our most popular, the standard 100 watt bulb, is being phased out, in part due to Clean Energy Act signed into law by President George W. Bush in 2007.  The maximum wattage incandescent bulb allowed will be 29 watts by 2014, down 70 percent from pre-2011 levels.

Instead, that type of bulb will be replaced by lower wattage incandescent bulbs, as well as compact fluorescent bulbs and even light-emitting diodes.

We can save lighting energy by

1. Turning off unused lights

2. Changing the type of light bulbs we use (see chart)

3. Changing the lighting plan, including adding natural light in the form of windows and skylights and solar tubes.

For more information about design, see the Energy Savers website.

Light can be measured in lumens. A 100 watt incandescent light bulb gives off around 1750 lumens.

The standard light bulb has a tungsten filament that exhibits incandescence when electric current travels through it. The filament burns out over time. The bulb keeps the filament in a special gas atmosphere like argon, instead of being exposed to regular air. Tungsten halogen bulbs operate somewhat similarly, with an incandescent filament, but the bulb contains halogen gas, which helps keep the filament from burning out as quickly.

Compact fluorescent bulbs, the sometimes spiral-looking bulbs, fluoresce instead of incandesce. Electric current travels through argon gas and a small amount of mercury vapor, which emit ultraviolet light. That light, in turn, excites a phosphor (fluorescent) coating on the inside of the bulb, which then emits visible light. So called CFLs are far more efficient and have much longer lifetimes. They do, however, contain a small amount of toxic mercury vapor and shouldn’t be thrown into the trash.

LEDs are also much more efficient than incandescent bulbs and don’t emit mercury if they’re broken. This technology is  sometimes called Solid State — even though the type of physics that the name is based upon has now changed to Condensed Matter. Extremely long-lived and very energy efficient, LED’s use around 20 percent of the energy of an incandescent for the same amount of light. However, they are far more expensive than similar fluorescent or incandescent options. For more about how LEDs work, go here.



Heating and cooling take a lot of energy. Replacing heaters, refrigerators, and single-paned windows costs money. Ripping out walls to add insulation is scary and can become a huge project.

However, today, a wide array of tools and professionals are available to assess the efficiency of heating and cooling and put it into perspective with cost. Home efficiency experts can use infrared detectors to track where heat is lost, and they can use blower door tests to check how quickly air is being exchanged with the outdoors through holes and leaky ducts.

Blower door tests change the air pressure inside a building relative to the outside to measure how quickly the air pressure returns to normal. If you walks through a pressurized house during the test, you can also track where air is leaking.

Even without a professional, you can reassess your home energy use. For tips on do-it-yourself home energy assessment, try the U.S. Department of Energy’s Energy Savers website.



1. Repairing leaky ducts, an often neglected source of heat loss! Ducts are much easier to access than replacing insulation, and they often have holes and cracks, making them a major  source of cold air infiltration, and also indoor air pollution.  Leaks suck in cold, dirty crawl space air including asbestos, dirt, and volatile chemicals (paint thinners, pesticides) that we stow or spray under the house. For more about indoor air quality see the Environmental Protection Agency’s website here.

2. Improve insulation and weather stripping, and seal up cracks. Use curtains or blinds to trap heat in during the winter and block sun out during the summer.

3. Replace air conditioners and heaters with more efficient models.

4. If you live in a dry climate, open windows to vent your home in the evenings, keep windows closed and A/C on during the morning before its the hottest hour of the day. Resist cranking the A/C up during the hottest hours of the day when the coolant fluid is the least efficient.

5. Replace windows and doors with better rated ones. For more about how windows are rated see the National Fenestration Rating Council.



The invention of new electricity-dependent devices outstrips the speed that we are making our homes more efficient. Today, heating, refrigerators, and air conditioners are using less energy, but televisions, computers, and an ever-expanding selection of other electronics are demanding more. For more about electricity in the home see the Basics of Electricity and how energy moves through the home.



A British thermal unit – almost always written Btu or BTU – is a measurement of thermal energy.  The scientific community usually uses the more manageable unit of the joule, which is a metric measurement of energy.  (A Btu is roughly 1,000 joules) A Btu is the English unit.

Fuels are often measured in Btu to show how much potential they have to heat water into steam or provide energy in other ways, like to engines. Steam turbines produce most of the electricity in the United States.


For more about the Smart Grid go to the Power Grid Technology section.

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Electric Vehicles 19th Century to Today


New York City in 1913.

Early 1800s Steam train travel becomes popular.

1850s Americans begin installing streetcar tracks. Street cars are steam-powered.

1859 Gaston Plante invents the lead-acid battery, though not specifically for transportation applications.

1880 Camille Faure improves Plante’s battery by developing the grid-plate battery in 1880, leading to use with motor power.

1880 Several inventors and companies begin to produce basic automobiles powered by steam, gasoline, electricity, compressed air, hydraulics, levers, and anything else on hand both in the United States and Europe, though Europe is more advanced initially.

1881 First experiments using grid-plate batteries to power a “converted horse streetcar,” conducted by Nicole-Jules Raffard.

1881 Charles Jeantaud begins working with Camille Faure to build an electric propulsion system, which they test with several motors over the next decade.

1885 First practical automobile, a gasoline-powered machine, is in production in Europe: the one-cylinder, three-wheeler Benz.

1890 There are 64 battery-powered streetcars in Europe, a small proportion of the total fleet.

1891 William Morrison builds the first electric automobile in the United States.

1897 The Electric Vehicle Company begins producing Electrobat electric taxicabs in New York, the first commercially-produced electric vehicles

1890 The Lohner-Porsche hybrid electric car is presented at the Paris Exposition. This hybrid electric used both gasoline and a battery, not regenerative braking.

1900 In the United States, 4,192 cars are produced this year: 1,681 steam cars, 1,575 electric, and only 936 gasoline cars, according to the U.S. Census. Statistics may be unrepresentative because of the number of electric taxis sold.

1900-1920 Many makes and models of electric, gasoline, and hybrid electric vehicles become commercially available  in the United States.

1904 More than a third of all vehicles in New York, Boston, and Chicago are electric.

1908 Henry Ford rolls out the Model T, a gas-powered car that was mass produced, initially offering the car at $850 and serially reducing the price until it reached $265 by 1923.

1912 Charles Kettering invents first practical electric starter, eliminating an advantage that electric cars held over gasoline cars.

1929 Electric car fails to compete and fades out of popularity; they’re charged higher fees for their higher weight (due to batteries), they are limited to shorter distances with few charging stations, are not as powerful. At the same time the electric starter and cheap gasoline made gas cars more desirable.

1933-1945 A second, small wave of interest in electric cars begins in England and Europe, spurred by gas rationing and World War II. German, French, and Dutch automakers produced a handful of electric vehicles. Small number of European automakers produce electric cars for transport during gasoline rationing

1949-1951 Tama Electric Motorcar Company of Tokyo sells a small electric car during Japanese gasoline shortage. However, when gas becomes available again, the electric car is discontinued.

1951-1953 The Symetric, a hybrid electric car, is made in France in the mid-1950s using plastic in the body.

1960s Experiments in electric car include a small fiberglass three-wheeler and a hybrid electric car with a nickel-cadmium battery, as well as the more popular Enfield 8000 from England. Even so, only 106 Enfields were built. Ford builds an electric car, the Comuta.

1966 First U.S. bills recommending electric vehicles.

1970 Passing of California’s Clean Air Act signifies a new era where the state takes control of its own air quality standards

1970s Throughout the 70s several more electric vehicles that are designed, though not widely sold, including the AMC Electrosport, the Sebring Vanguard Citicar and the Elcar 2000. Nissan makes the EV4P with lead-acid and zinc-air batteries, while Marathon Electric Car Company of Canada makes hundreds of C-360 vans, with six wheels and a foam-core aluminum body.

1972 Victor Wouk constructs a hybrid from 1972 Buick Skylark for Federal Clean Car Incentive Program, which is subsequently killed four years later.

1990 California passes the Zero Emissions Vehicle Mandate in California, ordering that 2% of all cars sold in the state be zero emissions by ’98. The requirement extended to 5% by 2001, and 10% by 2003.

1990 General Motors introduces electric prototype car, the unfortunately-named Impact.

1990 There are 41 Stage I smog alerts in California or Los Angeles

1990 Ford produces the Ecostar electric utility van with regenerative braking.

1993 Toyota begins developing the Prius hybrid car, which can’t be plugged in but uses a battery to capitalize on regenerative braking.

1996 Electric cars hit California roads at the same time that the Sport Utility Vehicle begins gaining popularity

1996 The EV1 electric car from General Motors becomes available, but only by lease, not for purchase. It uses plastic body panels supported with aluminum, low drag, and is offered for lease only.

1996 By this time, the nickel metal-hydride battery has been developed to be large enough for a car, and this technology is used in many hybrid cars sold today.

1997 Toyota unveils the Prius hybrid car and begins sales in Japan.

1999 Honda Insight hybrid car arrives in United States.

1999 Toyota Prius arrives in California.

2001 General Motors sues the California Air Resources Board for the electric car sales quota. Other automakers join the suit against California regulators.

2000 California’s AB 2076 requires state agencies to set goals to reduce petroleum consumption.

2002 CA passes Assembly Bill 1493, regulating greenhouse gas emissions.

2003 The new model Prius released and becomes fashion statement.

2003 Various pressures kill the California electric car mandate, and automakers begin pulling their electric vehicles off the road, in some cases crushing or shredding the cars.

2004 By this time, there is only one General Motors EV1 left on the roads.

2005 California’s AB 1007 establishes statewide alternative fuels plan, reduce petroleum consumption by 15% by 2020.

2006 California passes Global Warming Solutions Act, AB 32, which sets limits on greenhouse gas emissions to be achieved by 2020.

2006 By this time almost all the electric vehicles on the road in California are gone.

2009 According to SB 17, the California Public Utilities Commission must develop smart grid deployment plan to integrate PEV technology, or plug-in electric technology.

2010 Nissan delivers the first U.S. customer the Leaf, an electric car with 100 mile range, a lithium-ion battery, and regenerative braking.

2011 The Tesla Roadster electric sports car is offered. It has a range of 245 miles but costs over $100,000.

2011 By this time, hybrids vehicles are available from Honda, GM, BMW, Ford, Mitsubishi, Toyota, Lincoln, Lexus, GMC, Hyundai, Kia, Cadillac, Porsche, Volkswagon and Ford.  Electric-only cars are available from Nissan and Tesla, as well as many neighborhood electric brands.

2011 California Energy Commission gives out millions of dollars to studying plug-in electric vehicles and energy storage.

2015 Date by which all major auto-makers have announced to produce plug-in electric vehicles, which allow “hybrid” cars with regenerative braking to be charged by plugging them in.

Click here to return to simpler timeline.


Anderson, Curtis D. and Anderson, Judy. Electric and Hybrid Cars: A History. North Carolina: McFarland & Company, Inc. 2005.
Mom, Gijs. The Electric Vehicle. Baltimore: Johns Hopkins University Press, 2004.
Taylor, Alex. “Toyota: the Birth of the Prius.” Fortune Magazine, February 21, 2006.
“Take Charge: Establishing California’s Leadership in the Plug-In Electric Vehicle Marketplace.” California Plug-In Electric Vehicle Collaborative
Pollack, Andrew. “General Motors Sues California Over Quota for Electric Car Sales.” The New York Times, February 24, 2001.
“Investment Plan for the Alternative and Renewable Fuel and Vehicle Technology Program,” California Energy Commission, April 2009.
DRIVE California’s Alternative & Renewable Fuel & Vehicle Technology Program.
Who Killed the Electric Car, Sony Pictures Home Entertainment, November 14, 2006.
U.S. Energy Information Administration

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