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Energy glossary

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Power Glossary

You shouldn’t need an advanced degree in physics to understand your options when it comes to heating and electricity. ChooseEnergy’s here to help! Our glossary will simplify complicated information to ensure that you understand every aspect of service and option available.

We have broken down many of the commonly used terms or phrases you might encounter to ensure you make an educated decision when it’s time for you to choose energy plans. If you keep these words in mind while choosing a provider or reading your Terms of Service, we’re confident you will pick the plan that’s right for you.

  • Absorption
    How energy is transferred and transformed from one material to another. For example, water that has been heated by the sun turns to steam and can be used to generate electricity.
  • Access
    The customer's legal right as stipulated in his or her contract to utilize energy systems as a method of transferring energy to a home or business.
  • Active Power
    The amount of power used by a device to produce work. Active power, also known as input power, is measured in watts.
  • Aggregator
    A broker who acts on behalf of a group of customers to negotiate a bulk energy rate from an energy supplier.
  • Amp-Hours
    The measure of the flow of current over one hour.
  • Ampere
    The unit of measurement for electrical currents: One ampere (or amp) is equal to the flow of one coulomb per second.
  • Angle of Incidence
    The angle between the direct impact of the sun’s rays and the surface of the solar panel. To get the maximum amount of solar energy, you want the panel to be perpendicular to the sun’s rays. Your solar installer will angle the solar panels to get the maximum amount of energy efficiency.
  • Antireflection Coating
    A material applied to the surface of a solar panel that reduces light reflection to increase light transmission.
  • Appliance Energy Efficiency Ratings
    A ratings system established by the U.S. Department of Energy to determine how efficiently appliances convert energy sources to useful energy.
  • Appliance Standards
    Standards codified by Congress for minimum energy efficiency. These apply to dozens of appliances such as refrigerators, freezers, air conditioners, dishwashers, ovens, pool heaters, television sets and more.
  • Array
    Several solar panels that are connected together in a single system.
  • Biofuel
    A type of fuel produced by biomass. One example is ethanol produced from corn.
  • Biomass
    A renewable energy source from plants and animals. Wood is an example of biomass that can be converted to biofuel.
  • Boiler
    Vessel where heated water or steam is produced from the combustion of fuels such as natural gas. Boilers are used for the space heating, electrical power production or industrial process heating.
  • Boiler Rating
    The heating capacity of a steam boiler. Can be expressed in Btu per hour, horsepower or pounds of steam per hour.
  • British Thermal Unit (Btu)
    A universal measure of energy consumption equal to the amount of energy needed to heat one pound of water by one degree Fahrenheit.
  • Broker
    A company that facilitates the sale and/or purchase of electricity between businesses and energy suppliers.
  • Capability
    The maximum load an electrical apparatus can accommodate for a specific period of time without exceeding approved temperature and stress limits.
  • Catalytic Converter
    An air pollution control device required in all automobiles in the U.S. and used in some types of heating appliances. The catalytic converter removes contaminants with a catalysis to transform them into carbon dioxide and water.
  • Ccf
    A unit of volume equal to 100 cubic feet, used by some utilities to measure natural gas.
  • Central Heating System
    A single appliance that supplies heating to areas of a building through a network of pipes or ducts.
  • Central Power Plant
    A large plant that generates power for distribution to multiple utilities and customers.
  • Central Receiver Solar Power Plants
    Also known as “power towers,” these plants use fields of tracking mirrors to reflect the sun’s rays to a single thermal receiver. This super-powered solar energy from a common thermal receiver produces high-temperature thermal energy that heats molten nitrate salts. The salts are then used to create steam that is then sent on to a steam turbine-generator, producing useful electricity.
  • Chimney Effect
    The tendency of heat to rise through a vertical passage, such as a chimney or building. This occurs because heated air or gas has a lower density compared to the surrounding air or gas.
  • Circuit
    A device that allows electricity to flow through it. A circuit also allows voltage to cross positive and negative terminals.
  • Circuit Breaker
    A device used to protect electrical equipment by breaking the electrical circuit if the circuit experiences an overload. For example, if you have several high-energy products such as hair dryers and space heaters plugged into the same circuit, the circuit breaker will turn off electricity to protect the items from frying.
  • Closed Coupled
    A system in which the fuel production equipment is either in close proximity or connected to the equipment using the fuel.
  • Codes
    Legal guidelines establishing minimum standards to regulate construction projects. Codes are in place to protect the health, safety, and welfare of people.
  • Cogenerator
    A class of energy producer that produces heat and electricity from the same fuel.
  • Coloumb
    A unit of electrical charge – a coloumb is the charge transported by a constant current of one ampere per second.
  • Convection
    The transfer of heat through air currents. For instance, the convection oven is able to heat or cook its contents with hot air circulation.
  • Current
    The flow of electricity through a conductor. Current is measured in amperes.
  • Decentralized Energy System
    Energy systems that supply individual or group energy loads.
  • Declining Block Rate
    A supplier rate usually only available to very large consumers. This rate is structured so that the per unit price of electricity decreases as the amount of energy used increases.
  • Demand
    The amount of electricity used at any given instant or averaged over a designated period of time. Demand is usually measured in kilowatts (kW) or megawatts (MW). “Peak demand” is the 15- or 30-minute period of highest electricity usage recorded over 12 months.
  • Deregulation
    In short, deregulation means that you now have a choice in who you purchase your electricity and natural gas from. In other words, you can shop around for the energy plan that’s right for you.
  • Design Life
    The period of time a system or appliance is expected to last at its design capacity without needing major repair.
  • Dispatching
    To control and schedule the generation and delivery of electric power to its destination.
  • Distributed Energy
    A term that describes an electricity system in which power is produced at many small sites across the grid rather than at a single large site, such as a power plant. Distributed energy, such as home solar, puts the production of electricity closer to its point of consumption, improving efficiency.
  • Distribution or Delivery Charge
    What you pay for energy delivery over the utility’s power and gas lines. This portion of your electricity bill will remain the same no matter who supplies your energy.
  • District Heating
    A heating system that services a cluster of buildings from a central boiler plant. Steam or hot water is piped to the cluster and used for space heating or hot water.
  • Double-Pane Windows
    Also called glazed windows, this type of window has two layers of glass separated by an airy space. Because each glass layer and air space reradiate and traps heat passing through, double-pane windows are more resistant to heat loss.
  • Dual Duct System
    This air conditioning system relies on two separate ducts: one is heated, the other is cooled. Mixing varying levels of air from each duct together provides the desired temperature.
  • Efficacy
    The amount of useful energy delivered per unit of energy input. One example is the visible light output relative to power input.
  • Electric Cooperative (Co-op)
    An electric cooperative is a customer-owned electric utility that delivers electricity to its members.
  • Electricity Facts Label (EFL)
    Like the nutrition label found on food, it discloses important information to Texas consumers about your energy supply. It includes the prices, the contract terms, the sources of power generation, and emission levels. The Texas Public Utility Commission requires all energy suppliers to provide an EFL upon request.
  • Emission
    A substance (often a pollutant) emitted from a system because of a process.
  • Energy Audit
    A survey that calculates how much energy you use and helps you find ways to conserve energy.
  • Energy Crops
    Both food and nonfood crops grown specifically for their fuel value. Examples of energy crops are corn, poplar trees, switchgrass and sugarcane.
  • Energy Efficiency
    A way of managing how much energy we use. Something is energy efficient if it can perform the same task with less energy, like a compact fluorescent bulb, which produces the same amount of light as an incandescent bulb, but uses one-third to one-fifth as much energy.
  • Energy Efficient Mortgages
    Home mortgages that take into account the energy efficiency of a home. If a home has cost-effective energy saving improvements such as appliances or windows, homeowners can contribute more income to their mortgage payment. Therefore, a borrower can qualify for a larger loan amount.
  • Energy Factor (EF)
    The measure of overall efficiency of a variety of appliances (i.e. water heaters, dishwashers, clothes washers and dryers).
  • Energy Guide Labels
    Labels placed on appliances detailing their energy efficiency and consumption performance under FTD test conditions.
  • Energy Services Company (ESCO)
    Energy Services Company, or ESCO, is another word for energy supplier. They have the ability to purchase electricity and natural gas for their customers and are the middlemen between the company that actually generates the energy and the local utility who delivers it.
  • Federal Energy Regulatory Commission (FERC)
    An independent regulatory agency within the U.S. that has jurisdiction over various electricity and natural gas matters including natural gas pricing and wholesale electric rates. FERC also licenses and thoroughly inspects hydroelectric projects and their related environmental impact.
  • Generation
    Generation refers to the production of electricity. Electricity can be generated from natural gas, nuclear, coal, wind, water, and solar energy.
  • Generator
    A machine that converts mechanical energy to electrical energy.
  • Geothermal Energy
    Energy produced by the internal heat of the Earth. It can be used for heating or for producing electricity.
  • Glazing
    Transparent material used to admit light while reducing heat loss. Used on windows, skylights, greenhouses and more.
  • Green Energy
    Green energy refers to environmentally friendly energy that is generated from sustainable or renewable sources such as solar, wind, water, or geothermal power.
  • Green Pricing
    The practice among some utilities of selling electricity produced from renewable sources at a higher cost than electricity produced from nonrenewable sources. Some people are willing to pay the green pricing premium for clean energy.
  • Greenhouse Gases
    Greenhouse gases such as carbon dioxide and methane are released into the atmosphere when fossil fuels such as coal and oil are burned. These gases contribute to climate change by trapping heat in the atmosphere.
  • Grid
    A grid refers to the electrical distribution network maintained by utility companies – otherwise known as the power grid.
  • Hybrid System
    A hybrid system is a combination of two or more power-generating methods within a single system, for instance a solar array with a generator backup.
  • Insulation
    Materials that are used to prevent or slow heat transfer into your home or business building. Insulation foam or roof batts can combat the loss of warmth during the winter or the they can combat the sun’s heat in the summer.
  • Investor Owned Utility (IOU)
    A provider owned by stockholders or investors. Sometimes called a private power provider, it contrasts public power providers owned by government agencies or cooperatives.
  • Kilowatt-hour (kWh)
    This is the unit of electricity that providers use to determine the rate they charge for electricity use. A kilowatt-hour refers to an amount of electrical power (measured in kilowatts) used over a given time (measured in hours). For example, if you ran an air conditioner with a power-level requirement of one kilowatt for an hour, you would use a single kilowatt-hour. Likewise, if you used a computer with a power-level requirement of 120 watts for eight hours, you would also use a single kilowatt-hour.
  • Kilowatt (kW)
    A unit of electrical power that measures the amount of energy either consumed or produced by a device. Many household appliances and machines require a certain amount of electrical power, measured in kilowatts, in order to run. For instance, an air conditioner has a power-level requirement of 1000 Watts, or one kilowatt.
  • Load
    Load refers to the total amount electrical power being used over a given period of time.
  • Load Forecast
    The estimate of power need for a future period of time.
  • Losses of Energy
    The energy that is converted to a non-usable form during the operation of a system.
  • Mcf
    An Mcf is a unit of volume equal to 1,000 cubic feet, used by some utilities to measure natural gas.
  • Megawatt-hour
    A megawatt-hour is equal to 1,000 kilowatt-hours or 1,000,000 watt-hours.
  • Megawatt (MW)
    A megawatt is a measure of electrical power equal to one million Watts.
  • Module
    A module is a collection of solar photovoltaic cells connected together in a single panel.
  • Municipal Aggregation
    Some states allow for municipal aggregation, in which local municipalities and counties negotiate a bulk energy rate for all the homes and businesses within their jurisdiction.
  • Municipal- or City-Owned Utility
    A municipal- or city-owned utility is a non-profit utility that is owned and operated by the municipality it serves. In Texas, city-owned utilities get to decide whether their customers can choose their energy supplier. Customers should contact their electric cooperative or city utility for more information.
  • National Electrical Code (NEC)
    The set of regulations for the U.S. to ensure electrical systems are designed and installed safely.
  • Net Energy Production (or Net Energy Balance)
    The net energy production is the amount of useful energy a system produces, minus the amount of energy required to produce the fuel.
  • Net Metering
    Net metering is a process that allows consumers with home solar panels to sell any excess energy produced back to the utility company. If your home solar panels produce more energy than you use, that excess energy can also be rolled over to next month’s bill.
  • Non-Renewable Energy
    Energy sources that cannot be replaced, remaining in finite amounts in the environment. Fossil fuels like coal, natural gas and crude oil are non-renewable energy sources.
  • Nuclear Energy
    Energy created by splitting radioactive atoms like uranium. Nuclear energy produces the problem of radioactive waste, which is extremely difficult to dispose of responsibly.
  • Ocean Energy Systems
    Energy that is harnessed from the waves, tides and thermal gradients of the ocean.
  • Off-Grid Electric
    An off-grid electric system is a stand-alone energy system that works independently from the main electrical power grid.
  • Off-Peak
    A period of low energy demand.
  • On-Peak
    A period of high energy demand.
  • On-Site Generation
    Energy generated at the site of where most to all of it will be used.
  • Outage
    A stoppage of the electric power supply.
  • Passive Solar Design
    A structure designed with specific elements that heat and cool the structure, without the use of mechanical equipment. Some passive solar design features include building orientation, window sizing and consideration of local climate.
  • Photovoltaic (PV)
    Photovoltaic refers to a method of converting solar energy into electricity. Solar panels are frequently referred to as photovoltaic panels or cells.
  • Power Purchase Agreement (PPA)
    A contract that defines the terms between an electricity generator (the seller) and one looking to purchase electricity, typically a utility or an independent energy supplier).
  • Price to Compare
    If you purchase gas or electricity from your local utility, the “Price to Compare” is a line item on your bill and is the benchmark you can use to compare the costs of different energy plans. If you can find a electricity or natural gas rate lower than the “Price to Compare,” it may be advantageous to switch your energy supplier.
  • Provider of Last Resort
    A stopgap energy provider who will supply your electricity and/or natural gas should the supplier you contracted with exit the market for any reason. Should this happen, Choose Energy can help you establish service with a new energy supplier.
  • Quotas for CO2 Emissions
    A share of the total allowable CO2 emissions assigned to a country (or group of countries) within an outline of the maximum total emissions allowed for the planet. The United States has the highest level of CO2 emissions of all developed countries.
  • Radiant Barrier
    A reflective foil sheeting that displays low radiant energy transmission and can even block radiant heat transfer. Radiant barriers are usually installed in attics to reduce the amount of heat that flows through the roof to the living space.
  • Radiant Heating System
    Heating system in which heat is radiated to rooms through heated surfaces. These heated surfaces include hydronic radiators and electric resistance elements.
  • Radiator
    A heating device that utilizes hot water or steam to deliver heat to a room through natural air flow or pumping from a boiler.
  • Real-Time Pricing
    When energy costs change according to the time of day. Utilities will post the rates ahead of time and consumers will be able to plan their energy usage accordingly, running appliances that draw more power at times when energy is cheaper.
  • Recirculated Air
    Air that is taken from a heated or cooled location, cleaned and reconditioned, and then returned to the space.
  • Refuse-Derived Fuel (RDF)
    Renewable power fuel derived from combustible municipal solid waste (MSW).
  • Renewable Energy
    Renewable energy refers to energy that is generated from renewable sources, like wind, geothermal and solar power.
  • Renewable Energy Certificates (REC)
    Also known as a Renewable Energy Credit, a REC represents one megawatt hour (mWh) of energy generated from a renewable source, such as solar or wind. By purchasing the REC from someone who has generated renewable energy and fed it into the grid, consumers can offset their own fossil-fuel generated electricity. In effect, RECs allows consumers to certify that a portion of their energy came from a renewable source.
  • Rescission Period
    Also known as a Renewable Energy Credit, a REC represents one megawatt hour (mWh) of energy generated from a renewable source, such as solar or wind. By purchasing the REC from someone who has generated renewable energy and fed it into the grid, consumers can offset their own fossil-fuel generated electricity. In effect, RECs allows consumers to certify that a portion of their energy came from a renewable source.
  • Restructuring
    The Public Utility Holding Company Act of 1935 changed the structure of the electrical power industry by taking away certain territories’ utility monopoly and allowing open competition between power suppliers for the areas’ customers.
  • Retail Electric Provider (REP)
    A company that sells electricity to customers. All Retail Electric Providers must be certified to do business by their local Public Utility Commission. In Texas, some REPs are owned and operated by local utility companies, who are also responsible for delivering electricity. These companies are called Affiliated Retail Electric Providers.
  • Selectable Load
    A device that is plugged into a central power system but only used occasionally and intermittently, such as light fixtures, televisions or power tools.
  • Solar Cell
    The photovoltaic device that converts sunlight into electricity. Multiple solar cells are combined within a solar panel in order to generate a sufficient amount of electricity.
  • Solar Energy
    Electromagnetic energy given off by solar radiation. Solar energy can be harnessed and used to provide heating and electricity for homes and businesses.
  • Solar Gain
    The amount of solar energy a building absorbs from various entry points. Solar energy can pass through windows, conduct through the exterior to the interior or even be absorbed through materials within the building.
  • Solar Lease
    A financing method for home solar installation. It refers to an agreement in which a homeowner pays a monthly fee for use of the solar panels. Solar leases typically last for between 15-25 years. The advantage of a solar lease is that you don’t have to pay any upfront costs to go solar.
  • Solar Panel
    A collection of solar cells mounted within a frame for use in a solar PV system installation.
  • Solar Power Purchase Agreement (PPA)
    A financing method for home solar installation. It refers to an agreement in which a homeowner has a solar system installed at little to no cost. In return, the homeowner agrees to purchase the power provided by the solar installation – typically at rates well-below the market price.
  • Stand-alone
    A solar system that is not connected to the power grid. Stand-alone systems only provide electricity when they are receiving energy from the sun. Some stand-alone systems are connected to a battery bank for storing electricity generated.
  • Standby Power
    Energy being consumed by an appliance while it is not in use. For example, kitchen appliances that are turned off but able to be activated when needed.
  • Subsidy
    A government action towards the energy sector that lowers energy production costs, raises prices for energy producers or lowers energy prices for consumers.
  • Substation
    Electricity substations lay between the power plant and consumer on the electrical system. These locations are where voltage transformations occur.
  • Supply Charges
    The portion of your electricity bill that goes to pay for the actual energy consumed. It is also the portion of your electricity bill that you have control over. You can reduce your supply charges by comparing plans from different suppliers.
  • Tankless Water Heater
    Water is heated immediately when needed and distributed directly for end use.
  • Teaser Rates
    Some energy suppliers try to lure customers with teaser rates far below the going market rate. That teaser rate goes up after a few months, leaving the customer stuck paying much higher prices. By shopping with Choose Energy, you can be assured that there are no hidden costs or tricks with any of the plans on offer: what you see is what you get.
  • Terms of Service (TOS)
    Contract between an energy supplier and a customer that outlines fees, length of service, and other important information.
  • Therm
    A unit of heat used to measure natural gas volume. It is equivalent to the energy produced by one Ccf, or 100 cubic feet of natural gas.
  • Thermal Capacity
    A material’s ability to absorb and store heat for later use.
  • Thermal Energy
    Energy produced from heat energy.
  • Thermal Mass
    A material that stores heat, and therefore has a thermal capacity.
  • Tidal Power
    Energy harnessed from the rise and fall of ocean tides. The water is captured during peak tidal flow at a tidal power plant and is directed through a hydroelectric turbine.
  • Tilt Angle
    The angle between a solar array and the surface it’s mounted onto. This is different from the Angle of Incidence, which refers to the angle between a solar array and the sun’s rays.
  • Time-of-Use (TOU) Rates
    The fluctuating price of electricity based on the estimated cost of electricity during certain time blocks. Usually, TOU rates are divided per 24-hour period as well as by season. Real-time pricing, on the other hand, is based on actual prices during a time block (as opposed to estimated costs).
  • Tracking Solar Array
    Advanced solar panel array that follows the path of the sun to capture the maximum possible daily solar energy.
  • Transmission and Distribution Service Provider (TDSP)
    This is the company that manages the physical infrastructure that delivers power to homes and businesses.
  • Usage
    The measurement of energy used during the billing cycle. On your electric bill, the usage is measured in kilowatt-hours (kWh), while on your natural gas bill, it can be measured in therms, Mcf (thousands of cubic feet), or Ccf (hundreds of cubic feet).
  • Useful Heat
    Heat from a solar heating system that is stored above room temperature.
  • Utility
    This refers to the company that generates and delivers electricity to your home or business. Even if you purchase your energy supply from another company, the utility is still responsible for reliably delivering that energy to your home or business.
  • Variable Cost
    Total cost to produce energy, including fuel use, maintenance and labor. Variable cost does not include the fixed costs incurred whether or not the resources are operating.
  • Ventilation Air
    Air supply that is a combination of outside air and any recirculated, treated air.
  • Waste Heat Recovery
    The process of recovering and utilizing heat that would otherwise be released, unused into the atmosphere. For example, steam is frequently a wasted byproduct of heat and energy production but can sometimes be recovered to generate electricity.
  • “Your Rights as a Customer” (YRAC) Disclosure
    A document that informs you of your rights as an energy consumer. Energy suppliers must provide you with this disclosure as mandated by local authorities.
  • Zone
    An area within a building or home that must be cold, heated, and well-ventilated. Every zone in a home has its own thermostat to control conditions.