Demand

The amount of electricity that utility customers are using, or trying to use, at one time. (PG&E) It fluctuates throughout the day and night (see Demand Curve), and utilities must forecast those changes in order to bring more generation and power on the grid just before it is needed or less power when demand dips.

Demand Curve

If you use a line graph to track customer demand in a 24-hour period or throughout the year, it produces a curve showing those times of day or seasons of the year when power demand is up and when it is down. Utilities forecast customer demand for electricity so they can produce or purchase the power to deliver through the grid to meet demand. (EnergyMag)

DERs

DERs refers to Distributed Energy Resources – please see the definition of Distributed Energy Resources

Distributed Energy Resources

Distributed Energy Resources are often referred to as “DERs”

From the Advanced Energy Economy (AEE) Website: “DERs are physical and virtual assets that are deployed across the distribution grid, typically close to load, and usually behind the meter, which can be used individually or in aggregate to provide value to the grid, individual customers, or both. A particular industry interest seems to be centered on DERs — such as solar, storage, energy efficiency, and demand management — that can be aggregated to provide services to the electric grid.” (Distributed Energy Resources 101: Required Reading for a Modern Grid, on AEE.net)

One other definitionon DERs from ArenaWire in Australia as follows: “…small-scale units of local generation connected to the grid at distribution level….Common examples of DERs include rooftop solar PV units, natural gas turbines, microturbines, wind turbines, biomass generators, fuel cells, tri-generation units, battery storage, electric vehicles (EV) and EV chargers, and demand response applications. These separate elements work together to form distributed generation.” (Arenawire, March 2018)

DERs are advanced technology allowing for two-way power flow on the grid, so these units can generate power that flows back into the grid for use by other customers.

Distributed Generation

Distributed Generation is sometimes referred to as “DG”

Distributed generation is an approach that employs small-scale technologies to produce electricity close to the end users of power. DG technologies often consist of modular (and sometimes renewable-energy) generators, and they offer a number of potential benefits.  In many cases, distributed generators can provide lower-cost electricity and higher power reliability and security with fewer environmental consequences than can traditional power generators.  (Virginia Tech)

For example, rooftop solar would be a form of distributed generation. (AECT)