Study: Small solar arrays most cost-effective at two Taos water sites; utility limits and batteries complicate plans

Sauder Miller and Associates (SMA) presented a solar feasibility assessment on April 21 that examined whether the Town of Taos could replicate parts of its wastewater solar project at drinking-water facilities. The consultant, Dale Lyons, recommended proceeding first at two smaller well sites and flagged utility and operational limits that change project economics.

The study: SMA evaluated electric bills and site constraints at the town’s wells, arsenic treatment site and tank boosters and used NREL System Advisor Model simulations to size optimal net-metered systems. Lyons said Wells 3 and 4 — each capable of hosting about 50 kilowatts of ground-mounted photovoltaics, subject to shading mitigation — provide the clearest near-term financial case. “I would recommend proceeding with net metered solar development at Wells 3 and 4,” Lyons told the council.

Why it matters: Wells 3 and 4 are billed under a Kit Carson rate (rate 3) that charges primarily per kilowatt-hour, which makes net-metered solar more effective at lowering utility bills. Other key facilities — Well 5, Well 8, the arsenic booster and the 1,000,000-gallon booster — fall under a different Kit Carson rate (rate 4) that includes significant demand charges; net-metered solar does little to reduce demand charges.

Limits and workarounds: Kit Carson Electric is currently limiting net-metered interconnections because distribution-level daytime solar in its service area sometimes exceeds customer demand. Lyons said the utility’s current practice requires systems to stop exporting if a system would produce power that is not being consumed on-site. That constraint “limits your ability to generate power,” he said, and could leave a solar array idle during periods when wells are not pumping.

Lyons described two widely considered responses: (1) pair solar with battery energy-storage so daytime generation can be stored and used when the site consumes power and (2) work with the utility to define allowable export or to size batteries for specific sites. Batteries reduce export risk and can also blunt demand spikes, but Lyons cautioned they are costly; SMA has asked Kit Carson to provide distribution analyses and recommended the town wait for battery-sizing data before committing to battery-equipped systems.

Operational recommendation: Lyons also recommended the town investigate a suspected leak or pump inefficiency at the 1,000,000-gallon booster. His analysis showed steadily increasing energy use at that booster over 2022–2024, which he attributed to water leaking back through impellers or other check-valve problems; town staff confirmed repeated pump replacements in recent years and said Alpha Southwest is investigating.

Costs and paybacks: SMA’s case simulations estimated 50 kW ground-mounted systems at Wells 3 and 4 would reduce those facilities’ electric bills by about 30–60% and produce paybacks under 10 years if shading is reduced and net metering is available. At sites billed under rate 4, savings were much smaller and payback periods long unless paired with batteries or other rate-focused solutions.

Next steps: SMA asked Kit Carson Electric to model allowable battery sizes and to advise on distribution constraints; Lyons said SMA expects the utility’s analysis within weeks. The town also should continue to monitor pumping behavior and pursue the booster-pump investigation to control rising energy costs.

Ending: The consultant’s short-list — Wells 3 and 4 — gives the town two near-term options to reduce water-system energy costs, but execution will depend on shading mitigation, clearer utility interconnection rules and battery-cost calculations.