Does a real demand charge change when a water utility should run its pumps?

What it found

The 21,806 pump-10 schedules with at most two daily on-runs are simulated on EPANET’s Net3 (WNTR) at a 900 s step and billed on PG&E Schedule B-19 (secondary voltage, published rates effective March 2026): seasonal energy prices plus the peak, part-peak and any-time demand charges on the highest 15-minute kW. The shipped schedule peaks at 373 kW because booster pump 335 (about 310 kW) runs when tank 1 is low; its demand charges are 60–64 % of the shipped bill. Long lake-pump runs idle the booster and cut the peak to 63 kW, so the bill falls 56 % (summer), 66 % (winter) and 67 % (spring) with the tanks returned to within 0.1 % of daily demand (63–65 % with a 1 % tolerance), 62.5 % over a year. Pricing demand changes nothing about which schedule wins: the energy-only and full-bill optima are the same schedule, and stay so with demand rates scaled from 0 to 20 times. Time-of-use energy prices add under 1.5 points beyond the flat-energy optimum. The tariff is a real list price but not a tariff Net3’s size would be on (B-19 is mandatory above 499 kW), Net3’s demand is not seasonal, riders and taxes are left out, and it is one teaching network with a gravity river source.

A figure from its own output

Paper, code and results

• README and method
• Experiments and results
• Code
• Tests

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Produced with AI assistance (Claude). Results are from the code in this repository and are simulated or stylised unless the abstract says otherwise; nothing here implies affiliation with or endorsement by any lab, researcher or company cited. MIT licensed.