Electricity 101

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FREQUENTLY ASKED QUESTIONS

SYSTEM

POLICY

 

For other terms and concepts see the glossary.

 

Q: Why do other countries use different shaped plugs?
A: There is not only a physical difference between plugs, but also an issue of electrical incompatibility. There are various voltages as well as frequencies used throughout the world. For instance, in the United States, we use 110-120V (60 Hz), while in many other countries, 220-240V (50 Hz) is used. This is because the electrical standards were originally established by the individual countries and at the time, there was no international standardization. So… if you travel to another country, and you would like to take your favorite electrical device (e.g. digital camera, laptop, mp3 player) then make sure you also have an appropriate converter as well.

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Q: Why do outlets have three holes?
A: In the United States, standard (120 V) plugs have either two or three prongs. One vertical prong is electrically "hot"; the other (sometimes longer) vertical prong is "neutral". When an appliance or device is plugged into an outlet (or socket) and switched on, an electrical current will flow between the prongs and through the device circuit.

The third prong is the "ground" and is important for ensuring safe operation of the electrical device. It protects the user from dangerous electrical shock if for instance there is an electrical fault involving the appliance’s metal casing.

Back to top >

Q: Why do we have AC electricity?
A: At the turn of the century, there was differing opinion (especially between Thomas Edison and George Westinghouse) on whether electricity should be transmitted as alternating current (AC) or direct current (DC). This debate is commonly known as the "War of the Currents". AC had the advantage of being converted via transformers to higher voltages which, at the time, allowed electricity to be transmitted over long distances at lower losses.

Since then, technology improvements especially in the area of power electronics have enabled high voltage direct current (HVDC) applications. HVDC allows controlled transmission of large amounts of power efficiently over very long distances in narrower rights-of-way.

Back to top >

Q: Can we harness lightning as an energy source?
A: Lightning is very powerful and very dangerous. But lightning strikes are very brief and infrequent, and therefore the amount of energy that could be gained (and theoretically stored) would be small in comparison to overall electrical needs.

One lightning strike has enough energy (~1500 MJ) to power a 100W light bulb for almost half a year. However, you would need to harness over 58,000 lightning strikes each day to equal the electricity production capability of a large (1GW) power plant.

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Q: Can we have wireless transmission of electricity?
A: The wireless transmission of electricity is the transmission of electrical energy without wires. Conceptually, transmission of electrical energy is similar to the wireless transmission of information, e.g., radio or microwave. The major difference is that with radio or microwave transmission, you are focused on recovering the information, not all the electrical energy that you originally transmitted. The efficiency losses associated with wireless transmission of electricity would be high, and with current technology would not likely be cost effective.

Back to top >

SYSTEM

Q: What is electricity?
A: Electricity is the flow of electrical charge. It is a basic part of nature and one of our most widely used forms of energy. Everyday, we use electricity to do many jobs for us – from lighting and heating/cooling our homes, to powering our televisions and computers. More information >

Back to top >

Q: Where does electricity come from?
A: Electricity is a secondary energy source which means that we get it from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources. The energy sources we use to make electricity can be renewable (such as wind or solar) or non-renewable, but electricity itself is neither renewable nor non-renewable.

Back to top >

Q: What is the "grid"?
A: The "grid", or transmission system, is the interconnected group of power lines and associated equipment for moving electric energy at high voltage between points of supply and points at which it is delivered to other electric systems or transformed to a lower voltage for delivery to customers.

Back to top >

Q: How much electricity does a typical household use?
A: A household's electricity usage varies significantly, throughout both the day and the year. Typically, electricity usage will peak in the summer (due to air conditioning load). During the day, it will tend to be greatest in the late afternoon when people return home from work, they adjust their thermostats, and begin preparing dinner. The amount of electricity a customer uses over time is measured in kilowatt-hours (kWh).

On average, a typical household in the United States uses 920 kWh of electricity per month, with appliances accounting for 64.7% of electricity consumption. More information is available on EIA's electricity quick facts page.

Back to top >

Q: How did the electric system evolve?
A: When the electric system began over 120 years ago (starting with Pearl Street Station in NYC in 1885), generating plants were isolated and served dedicated customers. Over the next 50 years, "utilities" began linking multiple generating plants into isolated systems. By the mid-1930's, it was clear that connections between systems could bring additional reliability. They provided access to back-up generation in times of equipment failure, unexpected demand, or routine maintenance, as well as improved economics through reserve sharing and access to diverse energy resources. By the mid-1960's, the electric system had been transformed from isolated generators to an interregional "grid".

Back to top >

Q: What does the future look like?
A: One thing is certain – the future involves you. Despite strong efficiency improvements, average household consumption is expected to increase significantly over the next several decades. This will place stress on our existing infrastructure and highlight the need for additional investment in America's electric future. To address these energy challenges in an environmentally sustainable way will require creativity and innovation.

Back to top >

Q: Who owns the electric system?
A: The electric system, which includes generation, transmission, and distribution, is owned by a mix of entities. For example, 192 Investor-Owned Utilities (IOUs) account for a significant portion of net generation (38%), transmission (80%), and distribution (50%). About 2,900 publicly-owned utilities and cooperatives account for 15% of net generation, 12% of transmission, and nearly 50% of the nation's electric distribution lines. Approximately 2,800 independent power producers account for 40% of net generation. The Federal Government owns 9 power agencies (including 4 Power Marketing Administrations and TVA) with 7% of net generation and 8% of transmission. And 211 Electric Power Marketers account for approximately 19% of sales to consumers.

Back to top >

Q: Who runs the grid?
A: There are many entities involved in running the grid. There are generator operators and transmission owners. But from a system perspective, one of the most critical entities is the independent system operator or regional transmission organizations (ISOs and RTOs). They monitor system loads and voltage profiles; operate transmission facilities and direct generation; define operating limits and develop contingency plans; and implement emergency procedures. Reliability coordinators also play an essential role. For instance, NERC (North American Electric Reliability Corporation) develops and enforces reliability standards; monitors the bulk power system; assesses future adequacy; audits owners, operators, and users for preparedness; and educates and trains industry personnel.

Back to top >

Q: Who uses electricity?
A: There are over 140 million customers of electricity. They can be divided into 3 categories: residential (122 million customers; 37% electricity sales); commercial (17 million; 35% sales); and industrial (<1 million; 28% sales).

Back to top >

Q: Where can I find out more about potential careers?
A: Not all careers in the electric industry require an advanced degree. Lineworkers, for example, are in strong demand. More information on this as well as other career paths.

Back to top >

Q: How can I improve my energy use?
A: You have already taken the first step – you are thinking about your energy use and ways that your action can not only save you money but also secure America's energy future. It can be as simple as replacing your old incandescent lightbulb with a compact fluorescent. Additional energy efficiency tips.

Back to top >

POLICY

Q: How is electricity regulated?
A: The Federal government, through the Federal Energy Regulatory Commission, regulates interstate power sales and service. State governments, through their public utility commissions or equivalent, regulate retail electric service as well as facility planning and siting.

Back to top >

Q: Where can I find out about State incentives for renewables?
A: Start with the Database of State Incentives for Renewables & Efficiency.

Back to top >

Q: What is a national corridor?
A: Section 216(a) of the Federal Power Act, as amended by the Energy Policy Act of 2005, directs the U.S. Department of Energy (DOE) to conduct a study every three years on electric transmission congestion and constraints within the Eastern and Western Interconnections. Based on this study, and comments concerning it from states and other stakeholders, the Secretary of Energy may designate a geographic area experiencing electric transmission capacity constraints or congestion as a "national interest electric transmission corridor" (National Corridor).

The 2006 National Electric Transmission Congestion Study examined transmission congestion constraints across the Nation and identified areas that are transmission-constrained. Based on this study, two National Interest Electric Transmission Corridors were designated in 2007, but they were invalidated by a federal appeals court in 2011.  The 2009 National Electric Transmission Congestion Study examined transmission congestion constraints across the Nation and identified areas that are transmission-constrained. It did not make recommendations concerning existing or new National Corridor designations. The National Electric Transmission Congestion Study released in September 2015 seeks to provide information about transmission congestion by focusing on specific indications of transmission constraints and congestion and their consequences. The study focuses primarily on historical trends over the past few years, and looks into the future to the extent possible.  

Back to top >

Q: Are we connected to other countries?
A: The Northeast blackout of August 14, 2003 made the point clear – the North American electric system is interconnected. 8 U.S. states and 1 Canadian province were affected by this reliability event, with 50 million people without power and between $5-12 billion in lost economic activity. See final report.

Indicators point to increased trade in electric energy between the U.S. and its trading partners in Canada and Mexico. This increase in trade is anticipated to spur economic benefits and improve operational flexibility, especially in the context of the reliable operation of the bulk transmission system. Within the Office of Electricity Delivery & Energy Reliability, the Transmission Development team is responsible for authorizing the export of electric energy and the issuance of permits for the construction, connection, operation, and/or maintenance of electric transmission facilities at the international border.

Back to top >



FREQUENTLY ASKED QUESTIONS

SYSTEM

POLICY

 

For other terms and concepts see the glossary.

 

Q: Why do other countries use different shaped plugs?
A: There is not only a physical difference between plugs, but also an issue of electrical incompatibility. There are various voltages as well as frequencies used throughout the world. For instance, in the United States, we use 110-120V (60 Hz), while in many other countries, 220-240V (50 Hz) is used. This is because the electrical standards were originally established by the individual countries and at the time, there was no international standardization. So… if you travel to another country, and you would like to take your favorite electrical device (e.g. digital camera, laptop, mp3 player) then make sure you also have an appropriate converter as well.

Back to top >

Q: Why do outlets have three holes?
A: In the United States, standard (120 V) plugs have either two or three prongs. One vertical prong is electrically "hot"; the other (sometimes longer) vertical prong is "neutral". When an appliance or device is plugged into an outlet (or socket) and switched on, an electrical current will flow between the prongs and through the device circuit.

The third prong is the "ground" and is important for ensuring safe operation of the electrical device. It protects the user from dangerous electrical shock if for instance there is an electrical fault involving the appliance’s metal casing.

Back to top >

Q: Why do we have AC electricity?
A: At the turn of the century, there was differing opinion (especially between Thomas Edison and George Westinghouse) on whether electricity should be transmitted as alternating current (AC) or direct current (DC). This debate is commonly known as the "War of the Currents". AC had the advantage of being converted via transformers to higher voltages which, at the time, allowed electricity to be transmitted over long distances at lower losses.

Since then, technology improvements especially in the area of power electronics have enabled high voltage direct current (HVDC) applications. HVDC allows controlled transmission of large amounts of power efficiently over very long distances in narrower rights-of-way.

Back to top >

Q: Can we harness lightning as an energy source?
A: Lightning is very powerful and very dangerous. But lightning strikes are very brief and infrequent, and therefore the amount of energy that could be gained (and theoretically stored) would be small in comparison to overall electrical needs.

One lightning strike has enough energy (~1500 MJ) to power a 100W light bulb for almost half a year. However, you would need to harness over 58,000 lightning strikes each day to equal the electricity production capability of a large (1GW) power plant.

Back to top >

Q: Can we have wireless transmission of electricity?
A: The wireless transmission of electricity is the transmission of electrical energy without wires. Conceptually, transmission of electrical energy is similar to the wireless transmission of information, e.g., radio or microwave. The major difference is that with radio or microwave transmission, you are focused on recovering the information, not all the electrical energy that you originally transmitted. The efficiency losses associated with wireless transmission of electricity would be high, and with current technology would not likely be cost effective.

Back to top >

SYSTEM

Q: What is electricity?
A: Electricity is the flow of electrical charge. It is a basic part of nature and one of our most widely used forms of energy. Everyday, we use electricity to do many jobs for us – from lighting and heating/cooling our homes, to powering our televisions and computers. More information >

Back to top >

Q: Where does electricity come from?
A: Electricity is a secondary energy source which means that we get it from the conversion of other sources of energy, like coal, natural gas, oil, nuclear power and other natural sources, which are called primary sources. The energy sources we use to make electricity can be renewable (such as wind or solar) or non-renewable, but electricity itself is neither renewable nor non-renewable.

Back to top >

Q: What is the "grid"?
A: The "grid", or transmission system, is the interconnected group of power lines and associated equipment for moving electric energy at high voltage between points of supply and points at which it is delivered to other electric systems or transformed to a lower voltage for delivery to customers.

Back to top >

Q: How much electricity does a typical household use?
A: A household's electricity usage varies significantly, throughout both the day and the year. Typically, electricity usage will peak in the summer (due to air conditioning load). During the day, it will tend to be greatest in the late afternoon when people return home from work, they adjust their thermostats, and begin preparing dinner. The amount of electricity a customer uses over time is measured in kilowatt-hours (kWh).

On average, a typical household in the United States uses 920 kWh of electricity per month, with appliances accounting for 64.7% of electricity consumption. More information is available on EIA's electricity quick facts page.

Back to top >

Q: How did the electric system evolve?
A: When the electric system began over 120 years ago (starting with Pearl Street Station in NYC in 1885), generating plants were isolated and served dedicated customers. Over the next 50 years, "utilities" began linking multiple generating plants into isolated systems. By the mid-1930's, it was clear that connections between systems could bring additional reliability. They provided access to back-up generation in times of equipment failure, unexpected demand, or routine maintenance, as well as improved economics through reserve sharing and access to diverse energy resources. By the mid-1960's, the electric system had been transformed from isolated generators to an interregional "grid".

Back to top >

Q: What does the future look like?
A: One thing is certain – the future involves you. Despite strong efficiency improvements, average household consumption is expected to increase significantly over the next several decades. This will place stress on our existing infrastructure and highlight the need for additional investment in America's electric future. To address these energy challenges in an environmentally sustainable way will require creativity and innovation.

Back to top >

Q: Who owns the electric system?
A: The electric system, which includes generation, transmission, and distribution, is owned by a mix of entities. For example, 192 Investor-Owned Utilities (IOUs) account for a significant portion of net generation (38%), transmission (80%), and distribution (50%). About 2,900 publicly-owned utilities and cooperatives account for 15% of net generation, 12% of transmission, and nearly 50% of the nation's electric distribution lines. Approximately 2,800 independent power producers account for 40% of net generation. The Federal Government owns 9 power agencies (including 4 Power Marketing Administrations and TVA) with 7% of net generation and 8% of transmission. And 211 Electric Power Marketers account for approximately 19% of sales to consumers.

Back to top >

Q: Who runs the grid?
A: There are many entities involved in running the grid. There are generator operators and transmission owners. But from a system perspective, one of the most critical entities is the independent system operator or regional transmission organizations (ISOs and RTOs). They monitor system loads and voltage profiles; operate transmission facilities and direct generation; define operating limits and develop contingency plans; and implement emergency procedures. Reliability coordinators also play an essential role. For instance, NERC (North American Electric Reliability Corporation) develops and enforces reliability standards; monitors the bulk power system; assesses future adequacy; audits owners, operators, and users for preparedness; and educates and trains industry personnel.

Back to top >

Q: Who uses electricity?
A: There are over 140 million customers of electricity. They can be divided into 3 categories: residential (122 million customers; 37% electricity sales); commercial (17 million; 35% sales); and industrial (<1 million; 28% sales).

Back to top >

Q: Where can I find out more about potential careers?
A: Not all careers in the electric industry require an advanced degree. Lineworkers, for example, are in strong demand. More information on this as well as other career paths.

Back to top >

Q: How can I improve my energy use?
A: You have already taken the first step – you are thinking about your energy use and ways that your action can not only save you money but also secure America's energy future. It can be as simple as replacing your old incandescent lightbulb with a compact fluorescent. Additional energy efficiency tips.

Back to top >

POLICY

Q: How is electricity regulated?
A: The Federal government, through the Federal Energy Regulatory Commission, regulates interstate power sales and service. State governments, through their public utility commissions or equivalent, regulate retail electric service as well as facility planning and siting.

Back to top >

Q: Where can I find out about State incentives for renewables?
A: Start with the Database of State Incentives for Renewables & Efficiency.

Back to top >

Q: What is a national corridor?
A: Section 216(a) of the Federal Power Act, as amended by the Energy Policy Act of 2005, directs the U.S. Department of Energy (DOE) to conduct a study every three years on electric transmission congestion and constraints within the Eastern and Western Interconnections. Based on this study, and comments concerning it from states and other stakeholders, the Secretary of Energy may designate a geographic area experiencing electric transmission capacity constraints or congestion as a "national interest electric transmission corridor" (National Corridor).

The 2006 National Electric Transmission Congestion Study examined transmission congestion constraints across the Nation and identified areas that are transmission-constrained. Based on this study, two National Interest Electric Transmission Corridors were designated in 2007, but they were invalidated by a federal appeals court in 2011.  The 2009 National Electric Transmission Congestion Study examined transmission congestion constraints across the Nation and identified areas that are transmission-constrained. It did not make recommendations concerning existing or new National Corridor designations. The National Electric Transmission Congestion Study released in September 2015 seeks to provide information about transmission congestion by focusing on specific indications of transmission constraints and congestion and their consequences. The study focuses primarily on historical trends over the past few years, and looks into the future to the extent possible.  

Back to top >

Q: Are we connected to other countries?
A: The Northeast blackout of August 14, 2003 made the point clear – the North American electric system is interconnected. 8 U.S. states and 1 Canadian province were affected by this reliability event, with 50 million people without power and between $5-12 billion in lost economic activity. See final report.

Indicators point to increased trade in electric energy between the U.S. and its trading partners in Canada and Mexico. This increase in trade is anticipated to spur economic benefits and improve operational flexibility, especially in the context of the reliable operation of the bulk transmission system. Within the Office of Electricity Delivery & Energy Reliability, the Transmission Development team is responsible for authorizing the export of electric energy and the issuance of permits for the construction, connection, operation, and/or maintenance of electric transmission facilities at the international border.

Back to top >