Study: Concord’s voluntary peak-alert messages reduced midday load by roughly 0.7 MW, saving thousands on capacity charges

An independent analysis presented to the Concord Municipal Light Plant board found that the utility’s voluntary peak‑alert messages — emails or notices asking subscribers to cut usage during forecasted high-demand hours — are associated with an average midday load reduction of roughly 0.7 megawatts during alert hours.

Professor Gilbert Metcalfe, an energy economist, told the board he analyzed CMLP aggregate hourly data from the summer months and used statistical controls including ISO New England load forecasts and local weather to account for the fact that staff call alerts on days they already expect higher demand. "When the peak alert is called... I find that load does in fact go down," Metcalfe said, reporting an estimated reduction of about 700 kilowatts per alert hour.

The analysis estimated the dollar value of that reduction primarily through avoided capacity charges in the ISO New England market. Metcalfe presented a range of annualized savings that vary with ISO capacity prices; in earlier years a megawatt of avoided peak reduced costs by much more than in 2023–24, when capacity prices were lower. Based on the modeled 0.714 MW reduction and recent price levels, the analysis estimated the program’s capacity cost savings in recent years at roughly $22,000–$32,000 per year. Metcalfe noted those savings can rise or fall substantially if ISO capacity prices change.

Metcalfe also quantified smaller avoided energy and pollution costs and stressed two caveats: (1) the alerts are infrequent (a small number of hours each summer), which limits statistical precision; and (2) some of the observed load reduction could be shifting to other hours rather than representing net energy savings, which would reduce avoided energy and emissions benefits though capacity benefits can still accrue if the annual peak hour is affected.

Board members asked how widely messages reach customers and whether the list could expand. Laura (CMLP staff) said roughly several hundred email addresses are signed up for the alert list and that staff routinely promote the service when customers enroll in rebate programs. Metcalfe said that with the ongoing AMI smart meter rollout, future analyses could use household-level hourly data and support more precise evaluation and targeted experiments.

Board members praised the study and recommended repeating the evaluation after TOU implementation and as smart-meter data become available to see how price signals interact with voluntary alerts. "Once we put a financial aspect where people are paying on-peak pricing, how does that change behavior?" one board member asked; others suggested the utility consider critical-peak pricing if capacity costs rise again.