Meeting Nantucket’s demand for electricity, today and tomorrow. Upgrading Nantucket’s Electric Grid

2 Serving Nantucket  Currently two undersea cables serve the electric demand to the island.  Due to increasing demands for electricity, a third cable is forecasted to be needed in about 15 years.  In an attempt to delay the need for the third cable, measures are currently being implemented through energy efficiency initiatives.

Bunker Road Generation Project

4  The existing generation is intended to serve as a back-up source of electricity in the event a problem occurs with one of the submarine cables that interrupts service to the island.  Currently, one of the undersea cables and generators would be able to provide electricity to most, but not all customers on Nantucket during the peak summer months.  If Nantucket experienced a long outage during the summer months, National Grid would bring large mobile, or "roll on," generators to the island to serve customers.  This Project will increase on island generation capacity and reduce reliance of roll on generation during a supply contingency.

5 Bunker Road Generation Project Phase 1: Upgrade Diesel Generation  Replace the two existing 3MW diesel generation units with a new 10MW diesel generator.  New generator would improve National Grid’s ability to serve customers if the island experiences a cable-related service interruption. Phase 1 Timeline: June 2016: National Grid issues request for proposal (RFP) for bidders to supply and install the generator September 2016: Deadline for responses to RFP December 2016: Final Design / Construction Start

6 Bunker Road Generation Project Phase 1: Upgrade Diesel Generation

7 Bunker Road Generation Project Phase 2: Install Battery Storage or Second Diesel Generator  National Grid proposing to install a Battery Electric Storage System (BESS).  Requesting information from industry experts to asses whether battery storage is cost-effective and viable solution.  If battery is not a feasible solution, National Grid will install a second 10MW diesel generator.  If battery is chosen, it would be the first of its kind at National Grid. Phase 2 Timeline: May 2016: National Grid issues request for information (RFI) June 2016: Deadline for responses to the RFI August 2016: National Grid to review proposals and determine which project will move forward

8 Bunker Road Generation Project Phase 2: Install Battery Storage or Second Diesel Generator

9 Example of Battery Electric Storage System (BESS)

Candle Street Station Flood Mitigation Project

Candle Street Flood Mitigation  National Grid is proposing to install flood mitigation controls at its Candle Street Substation.  The Project is part of a Company-wide effort to protect our major assets from floods based off of FEMA’s base flood elevation calculations.  National Grid has received approval to proceed with Phase One of the project through the Nantucket Conservation Commission and the Nantucket Historical Commission.  Project team is currently reviewing the current design and making modifications to the plan. 11 Timeline: May 2016: Project engineering team reviewing and reassessing the overall design October 2016: Construction Start Phase 1 Spring 2017: Construction Start Phase 2

Existing Protections  Sandbag Protection at Switchgear. 12

Type of Work Proposed 13  Phase 1 (Short Term)  Improve Sandbag Systems currently protecting the switchgear  Seal conduits at designated manholes and riser locations  Phase 2 (Long Term)  Permanently Raise Equipment  Switchgear  Transformer Panels

14 Public Outreach  National Grid is committed to keeping local officials, residents, businesses and community groups informed and educated on the status of the projects through public meetings, site visits and direct mailings.  Upcoming Events:  July 2016: Informational Open House highlighting the two projects.  August/September 2016:  Site Visit with Town officials to be scheduled if we proceed with battery option.  Informational Open House to inform stakeholders on the Company’s decision regarding the battery storage.