Home News and Features GMP Uses Stored Energy to Reduce Peaks

GMP Uses Stored Energy to Reduce Peaks

The Stafford Hill Solar Farm in Rutland. Photo courtesy of Green Mountain Power.

One of the major problems faced by electric utilities is periods of peak demand. Peaks can occuron days when it is hazy, hot, and humid, for example. On such days, as customers arrive home from work and crank up air conditioners, cook dinner, wash and dry loads of clothing, or take showers, the demand for electricity spikes.

When a peak occurs, the electric utility may be forced to look to the larger regional grid to purchase additional electricity to meet the demand. If the weather conditions that caused the peak are widespread, idle generators may be required to start up to meet the demand. This can be expensive, and, if those power plants use coal or oil, the electricity generated may be “dirty” in terms of carbon emissions.

Green Mountain Power is the world’s first utility company to be certified as a B Corporation, which means that, in addition to traditional business practices, it must meet certain standards of social and environmental performance.

Therefore, to help combat peaks, save its customers money, and cut carbon emissions, GMP started a pilot program in February called “Bring Your Own Device,” or BYOD. The program is based on using stored energy and on controlling electrical devices during a peak to reduce the need to draw on the power grid. According to GMP, peaks can happen about five to eight times a month and they can last an average of three to six hours.

Green Mountain Power customers who have home battery backup systems, high-speed electric vehicle chargers, and electric hot water heaters can sign up to allow GMP to draw from or control their devices when there are peak demands. In exchange, customers see a reduction in their electric bills.

When there is a peak, GMP will draw on all the enrolled systems in the BYOD program and add that energy to its own utility-scale energy stores in Rutland and Panton to help meet the demand.

Home battery systems that are eligible for the program include SolarEdge StorEdge compatible systems (e.g., LG), Sonnen batteries, Sunverge batteries, Tesla Powerwall 2.0 systems, and Pika Energy systems. The battery system must be used for home back-up power only, and some fees, such as integration and communication fees, may apply.

Customers who enroll a battery backup system for 10 years can opt for an upfront payment of $850 per kilowatt of storage enrolled up to a maximum of 10 kW. Alternatively, they can opt for a monthly credit on their bill for that period. Battery systems located in areas of the state where extra storage is needed most can get an extra payment of $150 per kilowatt enrolled. According to Josh Castonguay, GMP vice president and chief innovation officer, Green Mountain Power’s BYOD program offers the biggest upfront payment from a utility in the nation for enrolling a home battery system.

Owners of electric vehicles can enroll their high-speed chargers and allow GMP to control when the charger operates. “A typical home charger uses about six kilowatts when it is charging a vehicle,” said Castonguay. “If we can turn off that charger during a peak, we are reducing the peak demand by six kilowatts.”

Electric vehicle charging stations that currently are eligible for the program are ChargePoint, FLO, and JuiceNet systems. Electric vehicle owners will see a credit of $10 per month for enrolling their device.

Similar to car chargers, electric hot water heaters can be enrolled in the program. During a peak, GMP will take control of the heater, preheat water before the anticipated peak, then prevent the heater from coming on during the peak. A Wi-Fi capable control device may need to be added to the unit (only Rheem brand heaters currently come with the controls already installed). Customers will receive a $5 per month credit for enrolling their device. (Washington Electric Co-op has a similar program for electric hot water heaters.)

Note that the program relies on Wi-Fi for communications with all these systems, and a major requirement of the program is that customers must have and maintain an internet connection. If the internet becomes disconnected, GMP will alert a customer so the internet can be reconnected within 30 days.

According to GMP, enrolled customers will be notified at least four hours in advance of an anticipated peak via their smartphone or by other electronic methods.

Any energy drawn from a system to meet a peak will be replaced as quickly as possible after the peak has passed, and GMP will make adjustments when possible to avoid completely discharging a battery for the purpose of achieving grid benefits during or prior to a pending weather event that could create outages.

While it cannot guarantee that a battery system will be charged to a minimum level at all times, GMP will work to minimize these impacts to make sure customers have backup power.

Green Mountain Power also points out that if you are planning to purchase a battery backup system or an electric vehicle, you can act now and reserve a space in the pilot program.

“When deployed all together, using this BYOD network is like taking about 12,000 homes off the grid at one time,” said Castonguay. “We know our customers care about the environment and make smart choices about energy every day. Our stored energy network is a great tool to help reduce demand during peak energy use, and the added benefit is it cuts carbon emissions and costs for customers while helping to keep them safe and comfortable.”

According to Castonguay there are 40 systems registered in the program. Enrollment in the BYOD program is open through the end of September.