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Maximum Capacity This number is an estimate of
the total generation capacity serving the NEISO control area
as indicated in NEISO morning report.
The fact that a generator can serve load, and so is included in this
figure, does not mean that it will be operating or selling electricity
into the New England market 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 NEISO control area that can
feasibly operate that day. See Generation Outages for more detail.
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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 ISO in the form of voluntary
load reductions ("negawatts"), which are not included here.
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Current Load
"Load" is the technical term for total demand for electricity.
It is the amount of electricity that customers are pulling out
of the grid at any given moment. This amount is monitored in real
time by NEISO, and published every 5 minutes.
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Forecast Load
While the load changes every time someone turns on a computer or switches
off a light, on the average it can be predicted, given information
about the weather, the daily habits of individuals and businesses, etc.
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Outages Every morning the NEISO publishes a
forecast
for the quantity of generation that will be offline
during the day.
The outage figures are updated at 8AM Eastern time.
We use the previous day's figures until 4AM Eastern time as an estimate.
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Imports and Exports
New England trades electricity with its neighbors.
The NEISO is responsible for scheduling electricity coming into or leaving the
region, just as it is responsible for scheduling electricity traded
within the region. On this
website we display the net imports and exports, with a positive net meaning more electricity
is being imported to the NEISO 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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