Case file / Water and municipal
Buttonwillow Water District
A 2.35 MW DC tracker field on district-owned basin margin land, serving three pumping meters. The district shifted its own load by filling storage reservoirs in the generation window instead of buying a battery.
- Array
- 2,350 kW DC
- Inverters
- 1,900 kW AC
- Annual output
- 4,230 MWh
- Permission to operate
- September 2024
Specification
The numbers on the record
| Client | Buttonwillow Water District |
|---|---|
| Location | Buttonwillow, CA |
| Array rating | 2,350 kW DC |
| Inverter rating | 1,900 kW AC (DC to AC ratio 1.24) |
| Modules | 4,273 at 550 W |
| Structure | Single-axis tracker, 2.4 metre row pitch |
| Storage | None; load shifted through reservoir scheduling |
| Modelled annual production | 4,230,000 kWh |
| Specific yield | 1,800 kWh per kW DC per year |
| Load offset | 71 percent |
| Construction window | 22 weeks |
| Permission to operate | September 2024 |
What made it hard
The constraints
- Three separate service points with different tariff schedules and very different load shapes.
- Hardpan encountered at 1.4 metres across roughly a third of the parcel, causing pile refusal during the pull tests.
- A Rule 21 fast-track screen failure on the largest meter, which sent the application into supplemental review.
What we did about it
The approach
- Single-axis trackers selected after a yield study showed roughly 19 percent more annual kWh than fixed tilt at this latitude, enough to justify the maintenance overhead at this scale.
- Ground screws substituted for driven piles across the hardpan zone, with the racking layout adjusted so the transition fell on a row boundary.
- Reservoir filling rescheduled into the 10am to 3pm window, which flattened the evening peak without any storage capital at all.
- Interconnection application filed eleven weeks before the geotechnical report returned, so the supplemental review ran in parallel with the civil work.
Result
Outcome
- System size
- 2,350 kW DC / 1,900 kW AC
- Modelled annual output
- 4,230,000 kWh
- Load offset across three meters
- 71 percent
- Tracker gain over fixed tilt
- 19 percent more annual kWh
- Evening peak reduction
- 230 kW from scheduling alone
Buttonwillow Water District, Buttonwillow, CAThey told us to move when we pump before they told us to buy anything. That advice cost us nothing and saved the most.
More work
Other case files
Bring us the bill before you bring us the roof
Every project starts with twelve months of interval data and a load shape. The array comes after that, sized to what you actually use.
CSLB #1071482 (sample). Prevailing wage on public works. Engineers answer, not a call centre.