The initial results are in, and we residents made a significant difference in the amount of peak-hour electricity used at Kendal and Crosslands. We can be proud of that! It could only happen with the combined effort of hundreds of residents, all pulling in the same direction. I’ll get to those results below, but first a reminder of what this effort was about.

This past summer, a lot of us residents got involved in a “peak alert” program sponsored by the Energy Committee. We sought to reduce the use of the dirtiest generating plants in our region of the grid, and to save Kendal-Crosslands Communities money. I’ve had many questions about how well this project worked, and now I have some answers to share.

To review the context: we are billed for a “capacity charge” each month. It is a surcharge on our electric bill levied by the organization that manages our regional electrical grid (called “the PJM Interconnection”), according to how much electricity we use during peak periods on the grid. Only commercial customers (which Kendal is) must pay this charge.

The PJM capacity charge is based on the peak-usage hour during the five peak-usage days of the year. These are always hot summer days, because air conditioning demand is what causes the peaks. By avoiding the use of power during these peak hours, we could save a lot of money in surcharges and cause the dirtiest generators to run less.

That was the objective of our “peak alert” program (which Crosslands participated in as well).  

Predicting the peaks. No one knows in advance which days will be the five peak days. PJM determines that retrospectively in the fall. But during the summer, PJM does attempt to forecast demand seven days ahead. We used those forecasts to determine which days were potential peaks.

Based on the records of previous years, we knew that the hour of peak demand in the PJM territory was almost always either 4:00 to 5:00 or 5:00 to 6:00, so we set out to try to reduce our use of electricity between 4:00 and 6:00 on any day that might turn out to be one of the five peak days. We knew we’d need to save electricity on a dozen or more days in order to be sure of catching all five peak days.

When potential peak days came along, we sent notices to an email list (over 150 people signed up for it) and posted a message on the website. Later, during the Covid outbreak, we put up lawn signs where people would see them at the food pick-up locations. Ultimately, we designated 13 days as “peak alert” days.

We put out lawn signs like this one for each peak-alert day. Residents responded by turning off their air conditioning and avoiding use of appliances between 4:00 and 6:00 on those days.

On those days, we asked residents to “pre-cool” their residences before 4:00, then turn off their A/C until 6:00. We asked them not to cook, use hot water, or run washers and dryers.

We were able to pick the right days. PJM posts on its website the hour-by-hour details of past electrical demand on PJM’s region of the grid. Based on that data it is clear that the top five days were (in descending order) August 24, August 12, June 29, July 6, and August 26. All of these were among our 13 “peak alert” days.

All the peak days were hot here at Kendal and Crosslands, but they weren’t necessarily our hottest days, and they weren’t necessarily the days we used the most electricity. For PJM, the important issue is electrical demand for the region as a whole; and since the PJM region goes as far west as Chicago and as far south as Virginia, the weather can vary considerably across the region. PJM charges Kendal according to our use during regional peaks, not during our local ones.

Yes, we made a difference. The orange line in the first graph below shows the average electrical usage at Kendal, at 15-minute intervals, on all 13 peak-alert days. The blue line shows the usage on non-peak-alert summer days (between mid-June and mid-September). The shaded area is the 4:00-6:00 period during which residents were asked to conserve electricity. You can see that usage dropped off dramatically during that period. That means we were successful in saving electricity. On other days, usage did not drop significantly (blue line). The second graph shows that the same 4:00 drop happened at Crosslands, though not quite as dramatically.

The two sharp notches in Kendal’s orange line (at 7 a.m. and 1:30 p.m.) have to do with times when the Kendal campus was running on its backup generator (not grid electricity) and are not significant in terms of peak-day issues.

The upper graph shows summer electricity usage at Kendal; the lower one shows the corresponding data for Crosslands. The shaded area shows the 4:00 to 6:00 period when residents were asked to avoid using electricity. As the orange line on each graph indicates, the program was successful in lowering usage. The blue line shows that usage did not drop significantly at 4:00 on other summer days.

We residents are proud to know that our participation had such a dramatic effect. The program was an opportunity for all of us to come together to work on something that helps both our community and the environment, and we rose to the occasion.

OK, but how much did we save? It remains to be seen how much we saved, in electricity and in dollars. First, we have to know what our electricity usage would have been during the five peak hours if we hadn’t had the peak-alert program. To do this, we will need to determine what the formula is for our typical electrical demand, given the local temperature, then see how our much lower our actual demand was. That will give us a percentage of savings. We’re working on that.

To know our dollar savings, we need to know what PJM’s capacity charge will be for the coming year (it varies each year). We won’t know that until nearer the start of 2022, when we will start paying the monthly fee reflecting our summer usage on the five peak days this past summer. Based on the percentage we saved, and the PJM fee, we’ll be able to figure out approximately how much money our peak-alert program saved.

UPDATE: Our electricity supplier, Calpine, tells us that this program during the summer of 2021 will save us about $24,000 in capacity charges. The savings will show up in our electric bills for calendar 2022, reducing them by about $2,000/month. A similar program is planned for the summer of 2022, with savings to appear on our 2023 monthly bills.