A report on the “Grid of the Future” pilot, by Co-Founder Fortunat Mueller


In June, ReVision Energy wrapped up the ‘Grid of the Future‘ distributed energy resource aggregation pilot project with Efficiency Maine. The goal of this 18-month project was to explore the ways that aggregated control of behind-the-meter distributed energy resources (DER) can help lower costs for all ratepayers and accelerate the clean energy transition.

The pilot consisted of roughly 40 ReVision Energy customer households who installed battery energy storage systems, heat pump water heaters, electric vehicle chargers or mini-split heat pumps with smart thermostats. In exchange for a small rebate funded by the Efficiency Maine Innovation Program, these customers allowed ReVision to exercise limited remote control of those devices over the course of the pilot to understand and evaluate the potential for using customer sited devices to shape the overall load on the grid.

Over the course of the test period, typical remote control interventions were just a few hours in duration a handful of times per month, and included adjusting water heater setpoints, curtailing EV charging capacity, controlling battery system charge/discharge and controlling thermostat setpoints for mini-splits in either heating or cooling mode.

While the individual effects of these changes are small enough to hopefully be unnoticeable for the participating customer, when aggregated together over a sufficiently large number of devices they become significant. The ‘fleet’ can behave like a virtual power plant and can be a very valuable asset to the grid for both lowering costs and accelerating the adoption of clean energy.

While historically, grid planners considered customer load to be essentially unchangeable and saw their role as building generation and distribution capacity to match that load, increasingly those planners and policymakers recognize that ignoring the value of load flexibility is actually very expensive for customers, because peak loads are a primary driver of overall electrical system costs. A 2017 report from Massachusetts Department of Energy Resources concluded that the top 1% of hours of load in any given year account for 8% of the overall ratepayer costs, and that the top 10% of hours account for over 40% of costs. Clearly if there was a way to cost-effectively manage and eliminate those peaks, it would be a good deal for ratepayers.

In addition to saving ratepayers money, load or demand flexibility is also an important part of modernizing the grid to accommodate higher fractions of clean, renewable energy. As we finally move to confront the climate crisis resulting from carbon pollution from the burning of fossil fuels, states around the region are moving to aggressively increase the use of renewable energy to power their economies. As articulated in a report from the Rocky Mountain Institute, customer demand flexibility has the potential to accelerate that critical transition.

For our pilot we partnered with a software startup called ‘Virtual Peaker’ that has created a software platform to aggregate and control these devices in a simple and efficient way and who works with utilities around the country. Increasingly, so many of the appliances in our home are already ‘smart devices’ which are connected to the internet so that a customer can view them or control them via computer, a cell phone app or smart speaker, like Amazon’s Alexa and Google’s Nest Hub and others.

Virtual Peaker takes advantage of that existing internet connection to these devices by routing data and control commands through their own communication channels, rather than try to set up a direct communication link as many other DER control platforms do. So, for example, when Virtual Peaker wants to adjusts the water heating setpoint on a Ruud heat pump water heater, it doesn’t contact the individual device itself (which can be very complex and includes significant internet security challenges), but rather contacts the central Ruud server and sends the command there. That server is the same one that the customer uses when they adjust the water heater from their cell phone app. By using a device’s native controls and communications, Virtual Peaker can control (always with the customer’s permission, of course) just about any smart device you can imagine. And so at a time when customers are already buying these smart devices in ever-increasing numbers, the marginal cost to control them as a grid resource can be very low.

While we are still analyzing the data and pulling together the final report for Efficiency Maine, our pilot showed that all four of the devices that we included (heat pump water heaters, battery systems, EV chargers, mini-splits) were effective as an aggregated demand side resource at various times of the year. Some device types, in particular batteries and water heaters, are pretty much always available when needed, while others, like mini-splits, are obviously only available when they are being used.

For example, somewhat to our surprise, even on the hottest days of the summer, which tend to also coincide with the regional electricity peaks, only about a quarter of the mini-splits in our demonstration were actually being used in Air Conditioning mode (and thus available to have their setpoints adjusted temporarily to benefit the grid). This makes sense when you consider that most heat pumps in Maine are being sold primarily as supplemental heating systems to displace oil or propane consumption, given our relatively low penetration and need for air conditioning, but it does have implications when thinking about the value of those devices for summertime load flexibility.

Going forward, we hope that the experience and data generated by our pilot will be helpful both for Efficiency Maine, and for policymakers as they consider policies and programs to help reduce peak demand, as well as programs to accelerate beneficial electrification of transportation and heating/cooling which we expect to be critical components of the forthcoming recommendations of the Governor’s Climate Council.

We feel grateful for the opportunity to be contributing to this important learning and are especially grateful to all the amazing ReVision customers who participated in the pilot. We appreciate the trust you put in us and we applaud and admire your desire and willingness to be a part of helping to drive Maine’s clean energy transition.


Additional reading:

Rocky Mountain Institute’s “The Economics of Demand Flexibility”

Dr. Richard Silkman’s “A New Energy Policy Direction for Maine”