The biggest consumer of electricity in Manteca is your toilet.

Or more precisely it is powering the city facility that treats what we flush down the toilet.

The annual PG&E bill for the treatment plant is in excess of $1.3 million and continues to grow with every hook-up and every PG&E rate increase. Electricity is the biggest cost involved in running the wastewater treatment plant.

 The council on Tuesday may take the next step in a bid to whittle down long-term energy bills at the treatment plant. That’s when they will decide whether to proceed with a request for proposals to design and build a 2 to 3 megawatt solar photovoltaic and battery storage project at the West Yosemite Avenue facility.

The cost of such a solar power installation that could cover 15 acres making it the biggest solar facility in the South County is pegged at $6.5 million. The project budget has $4,925,000 set aside in the Sewer Maintenance and Operation Fund that ratepayers pay into.

The change in estimate cost is attributed to devising a more robust design that can minimize the need for PG&E power while taking into account changes in the industry that have improved electricity production as well as provide the mandatory protection for environmental concerns as required under state and federal laws.

Originally when the council in November of 2016 authorized staff to seek proposals to design a solar installation they were looking at 1 megawatt with the installation covering 5.5 acres costing $3.9 million.

In a memo to the council, Public Works Senior Engineer Bret Swain notes, “staff is aware that the estimate is greater than the total budget and will evaluate all proposal results. Any adjustments or appropriations for the project will be made at the time of project award.”

Public Works staff indicated in 2016 the project has an eight year payback while the life expectancy is 25 years. That means for 17 years the city will be getting free electricity to cover much of the treatment plant’s power costs.

The largest single solar installation serving the South County is the 1.6-megawatt Robert Schulz Solar Farm operated by the South San Joaquin Irrigation District to provide almost all the power needed for the surface water treatment plant that provides water to Manteca, Lathrop, and Tracy. It is helping to keep costs down for drinking water in the three cities. The solar farm is located next to the water treatment plant just west of Woodward Reservoir.

The largest aggregate solar installation, though, are all the panels operated at various Manteca Unified School District sites.

The solar panels that double as car ports over parking lots at some campuses generated 27 percent of the district’s power needs and is saving the district in excess of $500,000 a year.

The solar farm is one of two major green initiatives the city is now tackling.

Manteca is the only city in the Northern San Joaquin Valley moving to harness food waste and methane gas from the wastewater treatment plant that is now burned off with a flame to produce fuel to power the fleet of 20 plus municipal solid waste trucks.

The City Council meets Tuesday at 7 p.m. at the Civic Center, 1001 W. Center St.

To contact Dennis Wyatt, email dwyatt@mantecabulletin.com