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Connecticut's Real Time Electric Demand and Air Quality
Connecticut's Real Time Electric Demand and Air Quality


What is the CT Power Update Graph?

The CT Power Update Graph shows the amount of electricity being used on Connecticut’s electric system (i.e., the current demand), today's forecasted demand and past seasonal peak demand.

Does the Graph reflect system reliability?

No. The Graph is meant to educate consumers about how peak electric demand can impact cost and the environment.

What is peak demand and how does it affect the cost of electricity?

Peak demand is the highest point of real-time customer demand. The size or capacity of Connecticut’s electric system must be built to meet annual peak demand. So, although high peak demands only occur a few times each year, additional costs are incurred to meet this demand for electricity.

What is Current Demand?

Current Demand (the blue dot and value) is the real-time amount of electricity that Connecticut's homes, businesses, schools, government, etc. are using, measured in megawatts. The blue line shows the actual demand that occurred throughout the day.

What is Forecasted Demand?

Forecasted Demand is an estimate of the demand that will occur throughout the day. The forecast is provided by ISO New England and is represented by the gray line.

What does the red dashed line represent?

The red dashed line is an average of past seasonal peak demands. The goal is to keep the current system demand below the red dashed line to help control overall electric costs in Connecticut.

How do I interpret the Connecticut Power Update Graph?

The Graph compares Connecticut's current electric demand to the daily forecasted peak demand. It also shows past seasonal peak demands. The goal is to keep current demand below past peak levels to help control future electric costs. Success will be indicated whenever actual demand (blue line) remains below the historical peak (red dashed line). Historical peak demand is used to set a portion of our future costs. So, exceeding the historical peak, (blue line crosses the red dashed line) can increase costs in the future. However, if we can keep current demand below past levels we can control costs going forward.

When does Connecticut’s peak demand occur?

Connecticut’s peak demand—the highest coincident use of electricity—occurs between noon and 8 p.m. on weekdays. The highest peaks typically occur on hot, humid summer days and are driven largely by air conditioning. However, other appliances, such as pool pumps, dehumidifiers, dishwashers, and clothes washers and dryers also contribute to peak demand.

What's the difference between seasonal peak demand and Connecticut's annual peak demand?

The highest demand for electricity, CT's annual peak, typically occurs weekdays between noon and 8 pm, during the summer months of June through September; the summer seasonal peak. The non-summer peak demand that occurs during fall, winter and spring, is generally lower than the summer peak. We show seasonal peak values to remind consumers year-round about the benefits of reducing our peak use.

What actions can I take to reduce peak demand?

You can lessen peak demand by reducing “discretionary” electric use during Connecticut's peak hours, weekdays between noon and 8 pm. Appliances and devices that can lessen peak demand include pool pumps, dehumidifiers, dishwashers and clothes washers and dryers. Consumers are encouraged to avoid the use of these items generally during the peak hours of noon to 8 p.m. The reminder here is to “Wait 'til 8” to use major appliances. Note that while limiting the use of major appliances takes a big chunk out of discretionary usage, reducing the use of other, smaller devices adds up as well. Any reduction in unnecessary use of electricity will help relieve system demand.

Why do I need to be informed about the demand on our electric system?

Controlling peak demand and being energy efficient in general provides economic, environmental, and societal benefits, as follows:

Economic benefits. Current electric costs are partially driven by past years' annual peak demands. So, controlling peak demand today helps control future system-wide costs. High peak demand affects the wholesale price of electricity and can require higher costs associated with investments in transmission lines and generators to keep Connecticut's electric system reliable.

Environmental benefits. Many peak generating plants in service today are older, less efficient units that produce more harmful emissions. So, reducing peak demand can help improve air quality by requiring these plants to run less frequently.

Societal benefits. When the electric system becomes strained by high demand, Connecticut becomes vulnerable to power disruptions. These disruptions are commonly referred to as rolling brownouts (i.e., voltage reductions) and rolling blackouts (i.e., shutting off power for up to two hours) in varying sections of the state.

These benefits can be summarized as follows: “Taking actions to reduce peak demand can help control overall costs for everyone, lower harmful emissions and reduce the strain on Connecticut's electric system to maintain reliability.”

What is the Connecticut electric system?

The Connecticut electric system, sometimes referred to as the state power grid, consists of hundreds of miles of high-voltage electric transmission lines that carry electricity from generating plants in Connecticut and across New England to local distribution systems operated by Eversource, The United Illuminating Company and several municipal electric systems.

What is a megawatt?

One megawatt is equal to one million watts of electricity and provides enough electricity to power approximately 200 homes during periods of peak summer demand. The number of homes whose needs can be met by one megawatt varies by season, time of day and each homes' power demand. One megawatt can serve more homes in the middle of the night or during the spring and fall when the demand of each home is lower.

The map above shows eleven of Connecticut's air quality monitoring stations. Color coding for each station indicates the recent air quality for that area (i.e., green = good, yellow = moderate, red = unhealthy). The colors are based on the Air Quality Index (AQI), the higher the value the greater the level of air pollution and the greater the health concern. To make it easy for you to understand whether pollution is reaching unhealthy levels, EPA assigned specific colors to each AQI category.

Mouseover each location for real time AQI information, as well as ozone and fine particulate measurements.

Air Quality - FAQs

What is the CT Air Quality map?

The CT Air Quality Update map shows the location of Connecticut's air quality monitoring stations and a color code to represent the most recent air quality being measured. For more information visit

How many monitoring stations are located in Connecticut?

There are a total of 22 ambient air monitoring sites in Connecticut. Eleven of these sites measure ozone from April through September and nine sites measure fine particulate matter throughout the year. Visit the CT DEEP's air monitoring web page for more information.

How do I interpret the CT Air Quality Map?

Air quality is measured at specific sites in Connecticut, so those sites may not represent the air quality at your location. Air quality can often be highly variable from one part of the State to another, depending on weather conditions. Some pollutants, like fine particulate matter, can have more of a localized effect whereas ozone tends to be a more regional event. In the winter, ozone is generally low, but fine particulate matter can be elevated in river valleys and urban areas; therefore, one cannot always rely on the air quality measured at the closest site, but should look at several of the surrounding sites to help determine any local trends.

How can air quality affect my health?

Elevated levels of both ozone and particulate matter can have serious health effects, especially for those who are more sensitive to air pollution. Ozone can:

  • Make it more difficult to breathe deeply and vigorously.
  • Cause shortness of breath and pain when taking a deep breath.
  • Cause coughing and sore or scratchy throat. Inflame and damage the lung lining.
  • Make the lungs more susceptible to infection.
  • Aggravate lung diseases such as asthma, emphysema, and chronic bronchitis.
  • Increase the frequency of asthma attacks.
  • Continue to damage the lungs even when the symptoms have disappeared.

Particles can:

  • Aggravate heart diseases such as congestive heart failure and coronary artery disease.
  • Cause you to experience chest pain, palpitations, shortness of breath and fatigue.
  • Increase the risk of cardiac arrhythmias and heart attacks.
  • Aggravate lung diseases such as asthma and bronchitis.
  • Cause respiratory symptoms including coughing, phlegm, chest discomfort, wheezing and shortness of breath.
  • Also increase your susceptibility to respiratory infections.
Does power demand affect air quality?

During the summer season, ozone is produced on warm sunny days in combination with pollutants from fossil fuel combustion as well as volatile organic compounds. Power plants running on fossil fuels emit more ozone precursor pollutants (such as nitrogen oxides) during days of high power demand. Ozone production is increased during those days, especially when higher emitting power generators are called into service to meet the State’s energy demand. Therefore, it is in everyone’s health interest to limit power consumption on those days when high ozone concentrations are forecast.

When should I be concerned?

Whenever the AQI is forecast to be over ‘100,’ which is the level of ‘Unhealthy for Sensitive Groups.’ Please note that especially sensitive individuals may exhibit cardiac and respiratory symptoms below this level.

What actions should I take to improve air quality?

Here are some tips that the EPA recommends to improve air quality:

  • Conserve electricity;
  • Consider setting the thermostat setting a few degrees higher on your air conditioner in summer;
  • Consider setting the thermostat setting on your heating system a little lower in winter;
  • Participate in local energy conservation programs;
  • Look for the ENERGY STAR® label when buying home or office equipment;
  • Keep car, boat and other engines properly tuned, and avoid engines that smoke;
  • Car pool, use public transportation, bike or walk when possible;
  • Combine errands to reduce "cold starts" of your car and avoid extended idling;
  • Consider using gas logs instead of wood. If you use a wood-burning stove or fireplace insert, make sure it meets EPA design specifications and burn only dry, seasoned wood;
  • Mulch or compost leaves and other yard waste.

Tips for days when particle pollution is expected to be high:

  • Reduce the number of trips you take in your car;
  • Reduce or eliminate fireplace and wood stove use;
  • Avoid using gas-powered lawn and garden equipment;
  • Avoid burning leaves, trash and other materials.
How are AQI maps generated?

Air quality is constantly being measured and forecasted daily throughout the year in Connecticut. The two pollutants represented on the map are ozone and fine particulate matter. Each is measured separately and the highest air quality index that is measured at the site is represented as a colored circle on the map. When measured air quality reaches a specified level (i.e., green = good, yellow = moderate), the station color represented on the air quality map will change to reflect the current air quality.

How can I order EPA publications?

Air quality publications are available on the publication page of

You can have a positive impact on air quality and the cost of electricity in Connecticut simply by waiting until later in the day to run major appliances that don’t impact comfort. Controlling electricity use during Connecticut’s peak electric demand periods - weekdays, between noon and 8 p.m. - minimizes the use of expensive, fossil fuel, "peaking" power plants

What is Peak Demand?

  • The peak electric demand is when consumers use the most electricity.
  • Connecticut’s peak demand happens on weekdays, between noon and 8 p.m. when homes, offices, businesses, and schools are using electricity.
  • Demand is lower in the morning, later in the day, and on weekends and very low overnight.
  • So to make sure that electricity is available to meet these high demands, additional power plants are needed to stand ready to operate during those few hours that we need them.  These are sometimes called “peaking units.”

 Wait ‘Til 8

  • “Wait ‘til 8” is Energize Connecticut’s message to remind consumers about the importance of controlling peak electric demand.
  • Using appliances that don't impact your comfort before noon or waiting until later in the day will help to control peak demand and have a positive impact on air quality and cost.
  • Using energy efficient products like LED lights and  ENERGY STAR ® air conditioning for necessary electric use also helps to control peak demand.

Why does it matter?

Peak Demand Affects Air Quality

  • To meet peak demand we operate generators that burn fossil fuel and produce harmful emissions.
  • Connecticut’s highest peak demands happen during ‘heat waves’ - extended periods of hot, humid weather.
  • So the greatest impact on air quality happens during periods of very high peak electric demand.

Peak Demand Affects Cost

  • The cost to build, operate and maintain peaking units is included in everyone’s electric rates.
  • Peaking units generally operate to meet Connecticut’s summer peak demand.
  • Because peaking units operate only a few hours each year the cost per unit of electricity can be very expensive.

When do we experience very high demand for electricity?

  • Connecticut’s highest peak demands happen between late May and early September during hot, humid weather.
  • These extreme peak demands occur during only 100 hours each year, or about 1% of the time.
  • Although we know that high summer demand will occur between noon and 8 pm on weekdays, we can’t predict the day or the exact hour.

What can we do?

  • Air Conditioning – We’re not asking people to do without their air conditioners.  But increasing the temperature setting can reduce the demand that air conditioning places on our electric system. 
  • Pool Pumps – Run pool pumps early in the day or later in the evening and still get the job done.  Consider installing a timer if you don’t have one. 
  • Dishwashers, Clothes Washers & Dryers – Using these major appliances in the morning or later in the day can really help. 
  • Irrigation – You don’t normally think about electricity when you water your lawn. But whether you are on a municipal water system or you have your own well, the pumps that move water use a lot of electricity.

Saving energy year round

  • Do you have a home improvement wish list? Start with Home Energy Solutions. Receive an average of $1,000 on in-home services for only a $124 co-pay (no charge for income-eligible residents). Includes air sealing, LED lightbulbs and more!  
  • Time to replace old appliances? Need new light bulbs? Make sure they are energy efficient and ENERGY STAR® certified
  • UI customers can save money with Time of Use rates.

Wait ‘til 8 is a simple way to remind electric consumers about this important effort to conserve when it matters most.