Solar Glossary

The key Community Solar terms you need to know to understand our program and speak like a solar pro!

Alternating Current (AC) vs Direct Current (DC)

Alternating current (AC) or Direct Current (DC) refers to the direction that electricity flows within a current. One primary difference is the power source of the current. DC only flows in one direction and its power source is from batteries or fuel cells. Laptops and electric cars run off a DC. AC reverses directions of electricity flow in regular cycles and is generally used in wall outlets. On a solar farm, an inverter is required as part of the photovoltaic system to convert the power from DC to AC for distribution to the electric grid.

Bill Offset

NRG Community Solar customers will receive the credit value generated by the assigned portion of the NRG Community Solar farm in solar credits to help reduce their electricity bill. Depending on your home energy usage and the amount of solar production, the value of the solar credits could help offset your energy bill. The amount of your energy supply charges that are reduced, or offset, is your bill offset percentage.

Carbon Dioxide Emissions (Carbon Emissions)

The greenhouse gases produced from natural sources (like the ocean) and human sources (like transportation). Fossil fuels are the leading cause of carbon emissions from human activities. In the case of NRG Community Solar, one way the environmental impact of our program can be understood is by the offsets of carbon emissions made by the solar energy produced from our solar farms. For example, over the lifetime of a customer’s contract, the average NRG Community Solar customer could offset the carbon emissions equivalent of a car driving over 280,000 miles.

Calculation based on the estimated farm production of an average 7 kW allocation over the life of the Agreement. For more information about this calculation visit the EPA Greenhouse Gas Equivalencies Calculator.

Carbon Footprint

The total amount of greenhouse gases produced by an individual person, household, or group of people through their day-to-day activities. The sum of all individual carbon dioxide emissions in a particular time frame (usually one year) is that individual’s carbon footprint. Taking steps to reduce your carbon footprint helps the environment. To learn easy ways to reduce your carbon footprint, visit our blog.

Community Solar

Community Solar is a solar energy sharing energy program where solar energy is produced by a solar farm (or solar garden) at an offsite location. The solar farm is supported by local residents and businesses that can subscribe to a portion of the solar farm . In turn, the community members receive solar credits for the solar energy generated by their subscription. The model allows for locals to benefit from solar energy and support clean energy generation without taking the steps to install rooftop panels on their home and maintain them.

Delivery Charge

The delivery charge on your utility bill is the amount an energy customer pays for actual delivery of electricity to their home, which could include things like meters and power lines. The charge is usually based on a home’s kilowatt hours (kWh) of usage and is determined by a customer’s utility.  There is no delivery charge for solar credits under the NRG Community Solar program, and the delivery charge with the utility does not change when a customer signs up with NRG Community Solar.

Deregulated vs Regulated Energy Market

In deregulated markets, consumers have the option to choose an energy provider other than their local utility, or “energy choice.” Retail energy suppliers can purchase energy and partner with utilities to deliver the energy to a customer’s home. The retail energy supplier may offer competitive rates to a customer in short term lengths, typically from 6 months up to two years. In regulated markets, customers are required to receive energy supply from their local utility and retail energy partners cannot compete. Community Solar is active in regulated and deregulated energy markets. In deregulated markets, customers can still participate in the NRG Community Solar program even when they have enrolled with a retail energy supplier.

Energy Supplier

An energy supplier is the company that supplies your home’s power at a contracted kWh rate. The supplier is your local utility company, or, in deregulated regions, it could alternatively be a retail energy provider.

Energy Supply Charge

An energy supply charge is the cost for the supply of power directly to a residence. It is a line item on a utility bill, separate from a delivery charge, and priced by kWh for the amount of energy a home uses in a given period. NRG Community Solar customers do not pay a separate supply charge when they participate in our program.

Escalator

An annual payment rate or rate increase often included within long-term contracts. Depending on your location, some NRG Community Solar contracts include a fixed-rate escalator. This means that while your NRG Community Solar subscription rate will increase each year, it will increase at the same rate throughout your contract term, and no higher.

Fossil Fuels

The leading source of carbon emissions, fossil fuels are non-renewable energy sources like oil, coal, and natural gas. These fuels require mining or drilling for extraction and must be burned to produce electricity. Fossil fuels currently make up approximately 81% of U.S. energy demand. By supporting solar energy generation through a program like NRG Community Solar, customers can help reduce dependence on fossil fuels.

Greenhouse Gas Emissions

Atmospheric gases, like carbon dioxide, that absorb and emit radiation, thus trapping heat in the atmosphere and warming the planet. The leading source of greenhouse gas emissions in the United States is electricity production.

Interconnection

The process of connecting a source of electric power generation, like a solar farm, to the power grid.

Inverter

Inverters convert the DC power generated by a solar farm into AC power to supply energy into an electric grid that distributes the power to consumers.

Kilowatt

1,000 watts of electrical power.

Kilowatt hour (kWh)

The total energy of 1,000 watts over an hour. On an electric bill, the electricity cost is determined by the amount of energy used by a home. This is measured in kWh. The amount of energy used is then multiplied by your utility rate to determine your energy supply cost and delivery charges. The value of the solar energy produced by a NRG Community Solar farm is determined by the amount of energy the farm produces in kWh, multiplied by the contracted rate of solar power.

Megawatt

A unit of power equal to 1,000 kilowatts, or 1 million watts. Large community solar farms typically measure the solar power generation in megawatts.

Megawatt Hour (MWh)

A unit equivalent to 1,000 kilowatt hours.

Net Energy Metering

Net Energy Metering, or NEM, is a billing system where rooftop solar customers are billed for their home’s net energy use, after the output of the solar energy generated by their home is applied. If more solar energy is produced than energy consumed by the home, these credits may apply to the home’s meter. A total of  43 states plus D.C. have implemented net metering policies.

Net Metering Credits

Credits that are generated for the solar energy produced by a customer’s assigned portion of a solar farm each month. These credits can help reduce your energy costs over time.  Net Metering Credits is another term for solar credits, virtual net metering credits, or enhanced bill credits. For most regions, the Net Metering Credits are applied directly to a customer’s utility bill.

Permitting

One of the requirements a home owner must complete before a solar system can be installed on their property. The permitting requirements vary by state and can require significant time and cost. A benefit of Community Solar is that residents do not have to complete permitting requirements on their home to go solar. Instead, NRG Community Solar builds and operates a local solar farm so that a resident’s roof and the solar permitting requirements are no longer part of the process.

Photovoltaic Effect (PV Effect)

The process by which sunlight is converted to electricity.

Photovoltaic System (PV System)

The complete system that converts sunlight to electricity on a solar farm, from the solar arrays to the remaining necessary components like an inverter.

Power Grid (or Utility Grid)

The system that connects electricity to homes and businesses. The United States has three interconnected grids to ensure stability and meet demand: The Eastern Interconnection, Western Interconnection, and the Electric Reliability Council of Texas (ERCOT) which covers most of Texas. Each of these three interconnections are made up of many regional grid operators that balance supply and demand of electricity and ensure the reliability of power in the region. The solar energy generated by a community solar farm is delivered directly to the power grid, allowing for energy distribution.

Power Purchase Agreement (PPA)

An agreement between a customer and a solar system operator where the solar system operator owns, maintains, and operates a solar system, and where a customer purchases the solar energy produced each month at a set price per kWh.

Renewable Energy

Energy produced from naturally regenerating sources including solar, wind, water, and geothermal power. Renewable energy sources do not require burning of fossil fuels that release harmful greenhouse gas emissions for usable electricity, and are therefore considered clean energy sources.

Renewable Energy Certificate (REC)

A representation of 1 megawatt hour (MWh) of electricity generated from a renewable resource. NRG Community Solar customers do not own the RECs for the associated solar output of their farm portion, but do receive solar credits based on the production from their subscription.

Rooftop Solar

Placement of solar panels on the rooftop of a home or business for energy to generate solar power for that individual home or business. Rooftop solar requires adequate roof space and access to heavy sunlight, permitting and installation, and maintenance of the solar system by the home or business owner.

Solar Array

A group of solar panels connected together. A solar array is one component of a photovoltaic system, consisting of the combination of several solar panels. Many solar arrays ultimately create a solar farm.

Solar Cell

Also called a photovoltaic cell, a solar cell is component of a solar panel that converts sunlight into electricity via the photovoltaic effect (PV Effect).

Solar Credits

Credits that are generated for the solar energy produced by a customer’s assigned portion of a solar farm each month. These credits can help reduce a customer’s energy costs over time. Solar credits are another term for Net Metering Credits, Virtual Net Metering Credits, or Enhanced Bill Credits.

Solar Farm (or Solar Garden)

A collection of solar arrays in an ideally suited location that produce large quantities of solar power that is sent to the utility’s power grid for distribution.

Solar Farm Allocation

The portion of a solar farm assigned to a customer. NRG Community Solar customers are sized to a portion appropriate for their home or business.

Solar Farm Development Tracker

A customer resource that allows NRG Community Solar customers to track the phase of their assigned solar farm’s development. Depending on when a customer enrolls, a solar farm may be in a varying stage of development, from site selection and permitting to construction and interconnection before it is activated for solar energy generation. Customers can login to their online customer portal to monitor the tracker for their assigned farm and see when the farm has reached its milestones, including activation. Customers are not billed until the solar farm is active.

Solar Panels ( or Photovoltaic Panels)

A collection of solar cells used to generate solar power. NRG Community Solar uses industrial-grade panels on all of our farms which are tested for endurance and weather.

Subscription

NRG Community Solar customers are subscribed to a portion of a local NRG Community Solar farm. Customers pay the associated subscription fee each month once the farm is active, and are billed separately from their utility by NRG Community Solar. Customers continue to receive a separate bill from their utility for their monthly energy charges, with solar credits applied (in most regions).

Utility Company (electricity)

A power company that supplies electricity to a set of customers in regulated and deregulated markets. Utility companies price power supply at a kWh rate. Utility rates historically fluctuate and are unpredictable. The NRG Community Solar program can help consumers better manage their energy costs.

Utility Inspection

The inspection of a solar panel system (Community Solar farm or rooftop solar system) that is conducted by a utility company before interconnection (when the system is connected to the power grid). The inspection confirms all requirements have been met. NRG Community Solar coordinates all necessary inspections with the utility.

Virtual Net Metering

The bill crediting system used by Community Solar that enables crediting for solar energy generated from an offsite farm, rather than from an individual’s home. Massachusetts, Minnesota, and New York are among the top Community Solar states that offer virtual net metering.

 

Additional Sources:

https://www.elevateenergy.org/programs/solar-energy/community-solar/glossary/

https://hub.globalccsinstitute.com/publications/solar-powering-your-community-guide-local-governments-second-edition/glossary-and-related-solar-terminology

https://www.energy.gov/eere/solar/solar-energy-glossary

https://energycenter.org/solar/homeowners/frequently-asked-questions

https://mysolarhome.us/understanding-your-electric-bill

https://www.energy.gov/science-innovation/energy-sources/fossil

https://www.seia.org/research-resources/net-metering-state

https://www.energysage.com/solar/community-solar/pricing-models/

Additional Resources