Last week’s heat wave drove near-record demand for electricity in New England, leading the power grid operator to invoke a rarely used energy conservation program to take pressure off the system.
The program, known as “demand response,” pays large commercial users to cut their electricity use when power consumption begins to approach the grid’s capacity. On Friday afternoon, when near-100-degree temperatures led to the fourth-highest electricity use on record, grid operator ISO New England triggered demand response.
Within a half-hour, dozens of major energy users turned off lights, raised thermostats, and took other steps to save 200 megawatts of electricity — enough to power about 200,000 homes — to relieve pressure on the grid.
“It’s very reliable,” Henry Yoshimura, director of ISO New England’s demand-response strategy unit, said of the program. “It gives us confidence the system will work.”
Demand response is among the tools employed by ISO New England, utilities, and large commercial users to control costs and insure the reliability of the power system under extreme conditions, such as last week’s heat wave. Over the past decade, ISO New England has turned to demand response an average of about once a year.
The New England power system has a capacity of about 32,000 megawatts. If demand exceeds that capacity, then brownouts and blackouts can follow.
Peak power consumption across the region hit about 27,377 megawatts early Friday afternoon, when ISO New England triggered demand response to maintain a safe supply cushion in case a major power station or transmission line was unexpectedly knocked out somewhere in the region.
Large regional energy users — including Partners HealthCare; Acushnet Co. in Fairhaven, the manufacturer of Titleist and other branded golf balls; Massachusetts Institute of Technology; Harvard University; and dozens of other participants — agree in advance to cut their energy use if called upon.
Brokered through energy management companies such as Enernoc Inc. of Boston and Comverge Inc. of Atlanta, the prearranged agreements apply to more than 2,000 facilities in the region and can save a total of up to 500 megawatts of power within 30 minutes.
That is the rough equivalent of the amount of energy produced by a medium-sized power plant.
Participating companies benefit by receiving tens of thousands of dollars a year for taking part in the program.
Enernoc and Comverge get a portion of that money, which is ultimately paid by ratepayers, though the program is overseen by ISO New England.
Reducing consumption can be cheaper — and cleaner — than firing up so-called peaker power plants to meet demand.
“It’s a critical resource,” said Tim Healy, chief executive of Enernoc, whose 750-employee company has a command center in Boston with banks of monitors tracking the energy use of thousands of customers.
Well before peak power-use periods, Enernoc, Comverge, and other energy management firms work with companies on how to reduce their energy consumption without major disruptions.
For example, Acushnet has plans in place to turn off lights, adjust air conditioners, and use emergency generators.
“We wouldn’t necessarily be shutting down an entire wing of a plant,” said Bob Espindola, an energy systems program manager at Acushnet, which has four manufacturing facilities in New Bedford and North Dartmouth, and a packaging and distribution center in Fairhaven. “It’s a lot of simple things you have to do.”
Commercial energy users have other incentives to save energy during peak demand periods.
Electricity costs are at their highest then, and companies often get hit with additional “demand charges” by power generators if they use an especially large amount of electricity during peak hours.
Across New England, utilities also have implemented long-term energy efficiency programs to manage electricity consumption and reduce the need to build new, expensive power stations.
The region’s two largest electric utility companies, NStar, a unit of Northeast Utilities of Boston and Hartford, and National Grid, which has headquarters in Waltham, are running or plan to start pilot programs to test cutting-edge technologies that would give residential customers more flexibility and financial incentives to reduce energy use during peak-use periods.
NStar is currently in the last year of a three-year program involving about 2,000 customers who have Wi-Fi-controlled thermostats and pay different rates during the day. They pay less during off-peak periods, such as nights and weekends, and more during peak times, such as hot summer afternoons.
The goal is to see if residential customers, given the technological power, will reduce their energy use during higher-priced times of the day, said NStar spokesman Michael Durand.
Meanwhile, National Grid is expected to launch a residential pilot “smart meter” program in Worcester next year that would measure consumption of electricity in homes by the hour or even by the minute. That residential program is also part of an effort to see if real-time pricing of electricity can lead to substantial energy conservation during critical times of the year, industry officials say.