News About the North Bay Water Reuse Authority

Napa Sanitation District Awards Energy Contracts to Reduce Costs

June 16, 2015

Napa Sanitation District
Contact:  Jeff Tucker
Chief Financial Officer
(707) 258-6012

Solar Power and Energy Storage Projects Will Save Ratepayers Millions

Napa, California – Napa Sanitation District has awarded two contracts that combined will save millions of dollars for its ratepayers over the next 25 years.

In late May, the District executed contracts with SunPower Corp. (Nasdaq: SPWR) to build, finance, operate and maintain a 1-megawatt photovoltaic solar power array on Napa Sanitation District property north of the Napa Airport and south of Highway 29.  The system is financed through a 25-year power purchase agreement that provides the District with a long-term cost of electricity that is significantly less than expected utility rates, with no upfront investment.  The District estimates it will achieve savings of up to $2.9 million over the term of the contract.

“The District is constantly seeking out ways to lower its operating costs to keep rates low for its ratepayers,” said Jill Techel, Mayor of the City of Napa and Chair of the Napa Sanitation District.  “This agreement with SunPower will immediately save money through lower electricity bills, and those savings will continue to grow over time.”

In 2014, the District produced 33% of its own electricity by running a cogeneration engine using biogas collected from the wastewater treatment process. With the solar power project, the amount of self-generated electricity will increase to almost 60%.

The District has also contracted with Tesla Motors, Inc., to install a 1-megawatt/2-megawatt-hour Powerpack commercial battery system.  The Powerpack will allow the District to store energy that it produces itself at times when electricity costs are low, and then use the stored electricity during times of the day when electricity costs are high.  This will allow the District to lower its energy costs and its demand charges.

“The partnership with Tesla is great for our ratepayers,” explains Tim Healy, General Manager of the Napa Sanitation District. “It reduces financial risk to the District, and ratepayers benefit through lower energy costs.”

Annual energy savings are estimated at $110,000. PG&E is providing financial incentives to the project through a grant program designed to reduce peak stress on the electricity grid.

The SunPower solar power array will utilize single-axis SunPower® Oasis® technology, which positions the panels to track the sun during the day to maximize energy capture. The system will cover approximately 4 acres of District property next to the Soscol Water Recycled Facility (SWRF) on Soscol Ferry Road.  It is expected to produce 2.1 million kWh of electricity per year, which is enough power to run 192 households (based on the 2013 national average of 10,908 kWh per year per household – U.S. Energy Information Administration,

Tesla will build the Powerpack system at the SWRF, and will be approximately 10 feet wide, 10 feet tall and 50 feet long.  The 1-Megawatt system will be able to store 2 megawatt-hours of electricity.  Two megawatt-hours is enough electricity to power the average household for 67 days, or enough to power the SWRF for just over 3 hours.

Napa Sanitation District (NSD) provides wastewater collection, treatment, and disposal services to the residents and businesses in the City of Napa, Silverado Country Club, the Napa County Airport and several adjacent unincorporated areas. NSD also provides recycled water service to portions of southern Napa County. Covering 20 square miles, NSD has been serving the community since November 1945. For further information about the District, please see