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North America / Commercial & demonstration

Caterpillar Tucson Proving Ground Microgrid

Current status, energy mix, organizations, suppliers, equipment, controls, reported specifications, and project updates—with source-level citations.

CoverageDetailed public record
Named organizations3
System facts23
Sources reviewed9
Evidence reviewed2026-07-20

Caterpillar's off-grid Tucson Proving Ground main-site microgrid, installed in 2016 with Empire Power Systems, combines 528 kWp DC/500 kW AC of First Solar PV, a 500 kW short-duration lithium-ion/ultracapacitor storage system, and three 410 ekW Cat C15 prime diesel gensets under a Cat Microgrid Master Controller. A separate 2025 gatehouse project added a small 20 kW PV and 24 kW/56.8 kWh Cat XES60 storage microgrid. The two systems are separate subsystems at the same proving ground and their capacities should not be added as if one commissioning phase.

Research status
The main-site system has operated since 2016 and remains presented by Caterpillar as an off-grid reference installation. Public main-site sources state expected fuel/runtime reductions but do not disclose verified lifetime savings or a current annual solar percentage. Caterpillar separately documented a February 2025 gatehouse microgrid that was operating with nearly all gatehouse energy supplied by solar and storage and diesel use reduced by about 95%.
Historical classification
Industrial
Reported capacity
See component specifications
Coordinates
31.84395, -111.10029
Evidence note: “Every company” cannot be proven from public material alone. This page lists every organization found in the recovered record and reviewed sources, preserves unknown roles, and explicitly marks undisclosed controller or equipment details.
Report missing evidenceResearch methodology

Project delivery

Who was involved in Caterpillar Tucson Proving Ground Microgrid?

3 publicly identified organizations. Where a recovered source named a participant without explaining its work, the role remains explicitly unspecified.

Organization

Caterpillar

Site owner and supplier/integrator of the diesel gensets, short-duration storage, power electronics, switchgear, controls, monitoring, and the later XES60 gatehouse system. [5][6][7][8]

Organization

Empire Power Systems

Caterpillar dealer that installed and maintains the complete main proving-ground microgrid and had previously installed the site's gensets. [5][6]

Organization

First Solar

PV-module supplier and development collaborator for the 528 kWp main-site array. [6][7]

System evidence

Energy mix, capacity, and specifications

Values can describe different project phases, generation sources, storage systems, or other components. Source citations are attached to each figure so discrepancies remain visible.

Storage
NA [1]
Main-site PV
528 kWp DC / 500 kW AC, using both fixed-tilt and single-axis-tracking sections [5][6]
Main-site PV modules
4,800 First Solar thin-film modules rated 110 W each [6]
Main-site storage
500 kW short-duration hybrid lithium-ion/ultracapacitor system rated to provide approximately 12 minutes of supplementary power; no kWh nameplate was disclosed [5][6]
Main-site diesel generation
Three Cat C15 gensets rated 410 ekW prime each, approximately 1.23 MW aggregate [7]
Main-site load
Approximately 300 kW average in the detailed case study [7]
Gatehouse subsystem (separate 2025 project)
58 PV modules totaling about 20 kW plus a Cat XES60 rated 24 kW / 56.8 kWh and diesel backup [8]

Controls and hardware

Equipment and controller details

Manufacturer and model are shown only when a source names them. Generic descriptions are not converted into guessed product assignments.

01

Diesel gensets

Caterpillar — C15

Three units, each rated 410 ekW prime, serving the main proving-ground system. [7]

02

PV modules

First Solar

4,800 thin-film modules rated 110 W each, split between fixed and single-axis-tracking arrays. [6]

03

PV inverters

Model not publicly disclosed

Twenty 25 kW AC string inverters, 500 kW AC total; the reviewed source does not name their manufacturer or model. [6]

04

Energy storage and bidirectional conversion

Caterpillar

500 kW Cat storage package combining lithium-ion batteries and ultracapacitors with Cat bidirectional power inverters for fast transient and short-duration support. [5][6]

05

Microgrid controller

Caterpillar — Microgrid Master Controller

Coordinates PV, storage, gensets, and integrated switchgear; Cat Connect provides web-based monitoring. [6][7]

06

Gatehouse battery system

Caterpillar — XES60

Separate 2025 gatehouse unit rated 24 kW / 56.8 kWh with an onboard microgrid controller. [8]

Technical record

Architecture, performance, and project updates

Concise technical facts, milestones, operating results, and later developments. Dated notes distinguish historical design claims from current evidence.

  • General

    Described as one piece of a very big puzzle, the Caterpillar Tucson Proving Ground (TPG) is now enjoying the benefits of solar energy. [1]

  • General

    The new commercial offering pairs solar energy, with the reliability of Cat gensets and industry-leading energy storage technology. [1]

  • General

    Now, just a few steps from the roaring generator room that powers TPG, five acres of rolling desert hills are covered in solar panels. [1]

  • General

    The solar panels, manufactured by First Solar and installed by Empire Cat, are perfectly positioned to capture the abundant Arizona sun, reducing the genset requirements. [1]

  • General

    To account for these frequent, sudden and unpredictable drops in energy, the microgrid solution uses bidirectional inverters and energy storage in order to balance out the load. [1]

  • General

    This hybrid solution will reduce the facility’s diesel fuel use and emissions by 33 percent each year. [1]

  • Main-site control strategy

    The controller can shut all three diesels down when daytime PV and storage can carry the site, then restart generation as needed. Caterpillar's publication attributes materially greater savings to its integrated controller than an earlier third-party control approach, but this is a vendor-reported comparison. [6]

  • Forecast main-site benefits

    At installation Caterpillar forecast about 33% lower diesel use and 25% fewer genset operating hours. The reviewed sources do not present a measured multi-year result against those forecasts. [5]

  • Gatehouse measured result

    Caterpillar reported the gatehouse's diesel use falling from more than 500 gallons per month to under 25, a 95% fuel reduction and 97% runtime reduction, with about $6,000 in monthly savings. These figures apply only to the 2025 gatehouse subsystem. [8]

  • Project boundary

    The 20 kW/XES60 gatehouse installation and Caterpillar's 2024 automated mining-truck energy-transfer demonstration are distinct from the 2016 main-site microgrid. Only the gatehouse is included as a later electrical expansion; the mining-truck trial is not counted as microgrid capacity. [8][9]

Provenance

9 sources

Primary owner, government, university, supplier, and engineering sources are preferred. Archived references preserve claims whose original pages moved or disappeared.

  1. [1]
    Recovered Microgrid Projects record

    Internet Archive · Archived source · captured 2020-07-06

  2. [2]
    Caterpillar Press Release

    caterpillar.com · Archived source · captured 2020-07-06

  3. [3]
    cat.com/microgrid

    cat.com · Archived source · captured 2020-07-06

  4. [4]
    Caterpillar.com/sustainability

    caterpillar.com · Archived source · captured 2020-07-06

  5. [5]
    Proof from the Proving Ground: Tucson

    Caterpillar · Primary source

  6. [6]
  7. [7]
    Microgrid Case Study: Caterpillar Tucson Proving Ground

    Caterpillar / Electrical Generating Systems Association · Primary source

  8. [8]
  9. [9]

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