The town of Groton, MA (11,000 residents) doesn’t own a peaker plant and can’t pass huge capacity charges on to rate-payers. What it does have is a forward-thinking municipal utility—Groton Electric Light Department (GELD)—and now a second battery-centric microgrid called Groton II. Commissioned this month with developer Lightshift Energy, the project gives the town true islanding capability during ice storms, trims ISO-NE peak charges, and even earns a slice of ancillary-services revenue.
What makes Groton II notable
- Resource mix 3 MW / 6 MWh lithium-ion storage sited behind a dedicated 1 MW rooftop + carport solar array.
- Controller & market link Lightshift’s Gridware DER-MS provides grid-forming functionality and submits the battery into ISO-NE’s capacity, reserve, and frequency-regulation markets.
- Use-case duality During blue-sky days the battery shaves the utility’s monthly and annual peaks (saving ≈ $350 k/yr); during extreme-weather events the system islands town hall, police, fire, and the water-treatment plant in < 100 ms.
- Funding model $8.8 million turnkey cost: 60 % municipal green-bond, 25 % MA CES grant, 15 % SMART solar incentive—no rate increase required.
- Operational learning Groton I (1 MW / 2 MWh, 2022) proved the economics; Groton II more than triples capacity and adds grid-forming black-start, creating a template for other Massachusetts “munis” that serve 15 % of the state’s customers.
Why this single project punches above its weight
Small municipal and cooperative utilities often struggle to justify battery projects without diesel. Groton II shows that:
- Peak-reduction revenue can cover debt service when ISO-NE charges $90–110 /kW-yr for capacity.
- Grid-forming batteries pass the resilience test—keeping public-safety buildings powered through the multi-hour nor’easter outage that hit during pre-commissioning trials.
- Market participation is doable for a muni if the controller and ISO metering are integrated from day one.
Build the skills to replicate Groton’s approach
Designing a battery that can both island critical loads and play in wholesale markets requires peak-shave modelling, ISO interconnection know-how, and grid-forming inverter testing. The Microgrid Systems Certificate Program—developed by Telepath Systems and Cleveland State University—covers those skills, preparing engineers and planners to deliver municipal-scale storage microgrids that pay for themselves.