Rooftop Solar: A Key Player in New England’s Heat Wave Energy Relief

How Rooftop Solar is Helping New England Stay Cool During the Heat Wave
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As New England endures its first heat wave of the summer, electricity consumption is on the rise. Fortunately, the power grid is managing to keep up with this increased demand, thanks in large part to the contributions of solar energy.

Across the region, thousands of solar panels installed on rooftops, in parking lots, and along roadways are converting sunlight into electricity, providing much-needed support to the grid. This type of solar energy, often referred to as “behind-the-meter” solar, is generated at the locations where the panels are installed, rather than being managed by the organization that operates the power grid.

Historically, behind-the-meter solar has made only a modest contribution to New England’s energy supply. However, over the past 15 years, its growth has been impressive. Collectively, these small solar installations can now generate approximately 5,000 megawatts of electricity, surpassing the total output of all nuclear power plants in New England combined. By 2045, ISO New England, the regional grid operator, anticipates this capacity will more than double.

Behind-the-meter solar is particularly beneficial during peak energy demand, such as hot summer afternoons. Jeremy McDiarmid, managing director of Advanced Energy United, a clean energy industry association, noted, “On a hot summer day, everyone is using electricity, and we need every resource we can get. Behind-the-meter solar plays a pivotal role in keeping the lights on.”

During this heat wave, ISO New England predicts that demand for electricity will reach some of the highest levels of the summer. On a recent Monday, electricity usage peaked around 7 p.m. at approximately 24,380 megawatts—almost double the 14,400 megawatts recorded the previous Monday when temperatures were cooler. ISO New England does not include behind-the-meter solar in its official peak demand calculations.

On Tuesday, expected to be the hottest day of the week, electricity usage is forecasted to peak slightly higher, at 25,800 megawatts. Matt Kakley, a spokesperson for ISO New England, stated, “What we’re expecting this week is the highest demand we’ve seen this year. However, it aligns with our projections for the summer, and we expect to have the resources needed to meet consumer demand for electricity.”

The region’s power plants and renewable energy sources, such as wind and solar farms, should be capable of handling the demand. While ISO New England can’t monitor behind-the-meter solar production as it does with utility-scale solar farms, it employs sophisticated modeling systems to estimate their output, accounting for factors such as localized weather changes.

Kakley mentioned that behind-the-meter solar is considered in ISO New England’s decisions regarding which additional power sources to activate. With the string of hot, sunny days expected, he added, “We’re counting on it showing up.”

On Monday at 3 p.m., as temperatures in Greater Boston soared into the low to mid-90s, behind-the-meter solar significantly contributed to the region’s electricity needs. Data from ISO New England indicated that while households and businesses consumed over 26,000 megawatts of power, around 18%—approximately 4,700 megawatts—was supplied by behind-the-meter solar.

Joe LaRusso, manager of the Clean Grid Program at the Acadia Center, a nonprofit focused on clean energy advocacy, emphasized the benefits of behind-the-meter solar: “It is already benefiting New Englanders by reducing summertime peaks in energy demand.” Most of New England’s electricity is generated from natural gas and nuclear power, but during peak usage times, the grid often relies on “peaker plants,” which are older, more polluting facilities that can be costly to operate.

LaRusso pointed out, “Without behind-the-meter solar, New England would have needed to burn much more coal and oil to balance electricity supply with customer demand. It reduces the cost of meeting peak demand and decreases system-wide emissions, including harmful pollutants that can affect respiratory health.”

As evening approached on Monday, solar power generation declined, leading to an increase in oil production. By 7 p.m., oil and coal were responsible for about 1,900 megawatts of power on the grid. Looking to the future, LaRusso expressed hope that as more behind-the-meter solar installations and battery storage become prevalent, the region can rely less on peaker plants during heat waves.

In addition to providing a crucial source of emissions-free energy, advocates argue that behind-the-meter solar can help lower utility bills over time—even for those without solar panels. The grid, with its expensive transmission lines and substations, must be built to accommodate peak demand; therefore, a reduction in peak demand could lessen the financial burden on ratepayers.

Sean Gallagher, senior vice president of policy for the Solar Energy Industries Association, stated, “By generating power close to where it is used, rooftop solar alleviates stress on the grid and reduces the need for costly transmission upgrades. This translates to fewer power outages and lower energy prices for everyone.”