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NYISO Control Area
This graph shows data for the NYC / Long Island portion of the
NYISO control area only.
The NYCA contains the entire state of New York, and is
divided into eleven zones. NYC and Long Island are two of these 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 NYC and Long Island zones.
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 zones 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 zones 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 NYC / Long Island
zones of 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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