Supply of and Demand for Electricity for New YorkCurrent Energy
Supply of and Demand for Electricity for New York

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The power grid that supplies the electric current coming into your home or business is designed to maintain a dynamic balance between the consumer demand for electricity and the amount being supplied by generators. The chart above is an approximate representation of this dynamic balance. You may need to click your browser's reload button to update the graph.

The current demand (or "load") depends on how much power consumers are using right now. While the load changes every time someone switches a light on or off, the sum of loads due to a large number of consumers varies slowly. In addition to the supply needed to meet this demand, some "reserve" generating capacity must be kept ready to operate in case of any unexpected events.

The current load is published every five minutes by the New York Independent System Operator (NYISO) for the area it controls, which covers the entire state of New York. It is a little more difficult to quantify the amount of supply that may be available, which we call "Potential Capacity". Our approximation is based on: the total capacity of generators licensed to operate, minus the generators that are out of service (an approximation of forced and planned outages), plus imports, minus exports. Imports and exports are updated approximately every five minutes. Outages are based on semi-annual reports published by the NYISO.


NYISO Control Area This graph shows data for the NYISO control area only. The NYCA contains the entire state of New York, and is divided into eleven zones. A map of the NYISO control area and the zones can be found here . Within its control area, the NYISO is responsible for scheduling generation and load, contracting for all the services necessary to maintain grid reliability (ancillary services), and scheduling imports and exports.
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Maximum Capacity This number is an estimate of the total generation capacity inside the NYCA. It is computed as the sum of the online capacity of all the generators licensed to operate according to a document entitled Existing NYCA Generation Facilities, published by the NYISO and which can be found here. This number will be updated as appropriate. The fact that a generator is licensed, and so included in this figure, does not mean that it will be operating or selling electricity into the NYISO on any given day.
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On-Line Capacity On-Line Capacity is equal to the Maximum Capacity minus Generation Outages. It represents the total generation capacity in the NYISO control area that can feasibly operate that day. See Generation Outages for more detail.
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Generation Outages A generator that is off-line (unavailable to operate under any circumstances) is called an "outage" or a "curtailment". Outages can be scheduled in advance (usually for maintenance purposes), in which case they're known as "planned" outages. Or they may occur with little or no advance notice, in which case they're called "forced" outages. The NYISO publishes data on Generation Outages only twice a year in the NYISO seasonal Operating Study, which can be found here. In these reports, the NYISO publishes the scheduled (planned) generation outages and the allowance for unplanned (forced) outages for the entire season. These values are updated as new information is available.
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Potential Capacity The generation capacity potentially available to supply electricity is computed here as the sum of On-Line Capacity + Net Imports/Exports - Reserves . We use a reserve margin equal to 7% of the load. The generation capacity actually available in any given hour will differ from our estimate of the potential capacity for a variety of reasons. Hydroelectric capacity may be reduced due to water shortages. Some plants are only available a certain number of hours per month, or may have restrictions on their operation due to air quality concerns. There may also be resources available to the NYISO in the form of voluntary load reductions ("negawatts"), which are not included here.
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Current Load The current load is the total demand for electricity in the NYCA at the current time. It is published approximately every five minutes at the NYISO Open Access Same-Time Information System (OASIS) web site as an instantaneous snapshot of the actual load conditions. However, this number is subject to change when more accurate information is collected from the Transmission Operators. The values collected and published on this site are the initial ones posted by the NYISO. Any revisions published by the NYISO are not captured. For the most accurate data, please see the NYISO OASIS website.

Although the load varies every time anyone flicks a switch, on the average it's fairly predictable, with variations due to daily, weekly and seasonal patterns. Load that is fairly constant over the entire day is referred to as the "baseload"-- for residences, it includes such things as refrigerators, water heaters, and lights that are never turned off. Baseload for residential and commercial buildings can be surprisingly large, considering that there is little activity at night. Seasonal variations in load are due mainly to changes in the need for heating and cooling, and can be quite substantial. This is somewhat inconvenient in terms of managing supply, since generation capacity has to be built to satisfy the peak load, but for much of the year the actual loads may be much less.
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Forecast Load The forecast load (given for each hour) is published the day before the "real-time" day on the NYISO OASIS web site. For example, the forecast load for January 2, 2002 was published on the OASIS web site on the morning of January 1, 2002.
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Imports and Exports New York trades electricity with four of its neighbors - PJM Interconnection, Quebec, Ontario, and New England. The NYISO is responsible for scheduling electricity coming into or leaving the state, just as it is responsible for scheduling electricity traded within the state. On this website we display the net imports and exports, with a positive net meaning more electricity is being imported to the NYCA than being exported. Because electricity that is being imported or exported changes the available generating capacity within the state, the net import/export value is incorporated into the "Potential Capacity" value.
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Disclaimer:

Development and maintenance of the Current Energy website ended in January, 2005. Linkages to data obtained from other websites will degrade over time, and parameters on which the computations depend will become out-of-date.

This chart is presented for educational purposes only. We have used publicly available information, and cannot assume reponsibility forthe accuracy of this information. Links to the original data sourcescan be found at this page.

These pages were prepared by Emily Bartholomew, Chris Bolduc, Katie Coughlin, Brian Hill, Alan Meier and Robert Van Buskirk,
Environmental Energy Technologies Division
Lawrence Berkeley National Lab