La Porte wastewater plant reports 1-MW solar field, 13-year payback estimate and ongoing maintenance needs

Jerry, a city wastewater staff member, told the La Porte Sustainability Commission the city built a 1-megawatt solar field sited on land partly converted from corn and an old sludge lagoon and that the array was chosen over wind and expanded biogas because “solar would be simple,” the system has been “remarkably, trouble free” and it produces substantially more power than the plant needs during summer months.

The solar field supplies daytime electricity to both the treatment plant and NIPSCO under an existing net-metering agreement, Jerry said. He described a seasonal pattern: the plant uses about 250 kilowatts, the array can produce almost a megawatt in strong sun, and the plant builds a summer credit “bank” that reduces winter bills. Jerry said the plant currently sees about $25,000 in avoided electricity cost in high months and that annual solar production has ranged roughly from 1.1 million to 1.6 million kilowatt-hours in full years; partial 2025 production was recorded at 1.39 million kWh.

Staff presented a simple financial analysis showing total project financing of $3,480,000 (construction loan plus interest) and a revised payback period now estimated at about 13 years, owing partly to rising utility rates that increase the value of on-site generation. Jerry said panels are guaranteed for 20 years and typically last 20–25 years.

He also described equipment and monitoring issues. An infrared drone inspection identified roughly 30 panels needing replacement out of about 1,200. The system uses 18 central inverters that convert roughly 1,500 volts DC from the strings to AC; inverters are expected to last about 10 years, and one unit recently failed and required manual intervention. The original vendor that set up remote monitoring went out of business, leaving staff to pursue new monitoring that integrates with the city’s systems.

Jerry said the plant evaluated biogas production from the anaerobic digesters and found feedstock inconsistent after sources such as a food-waste program from Meijer ended. He described the digester process used at the plant, including heated digesters at about 95 degrees and a dome gas-holder, and said biogas is mainly used for process heat. Other cities he cited have used more concentrated food-waste inputs to produce enough gas for turbines or pipeline-quality gas, but La Porte’s available organics have been insufficient to change the plant’s energy balance.

On resilience, Jerry said the utilities department has added backup generators at pump stations, standardized pumps so units can be swapped between stations, and is evaluating packaged battery systems as an alternative to diesel generators for short outages. He noted batteries require less maintenance and produce no onsite emissions but provide shorter duration backup than generators.

Commissioners asked about net-metering value, battery integration and options to increase the plant’s percentage of annual usage met by solar. Jerry said that while the current NIPSCO agreement returns kilowatt-hours on a roughly even basis, changes in regulatory treatment of net metering have reduced sellback value for new systems and that the city secured its agreement before those changes took effect.