Foxtail Flats: Solar Power and Battery Storage

In 2016, the Los Alamos Board of Public Utilities (BPU) set a goal for the Department of Public Utilities (DPU) to become a carbon-neutral electrical energy provider by 2040. The Foxtail Flats Solar and Storage agreements will bring 170 megawatts (MW) of solar power from the Four Corners area as an energy resource for Los Alamos County, as well as 80 MW/320 MWh of battery storage. This project was approved by Council in February 2024. The Foxtail Flats project is being built by DESRI (D.E. Shaw Renewable Investments).

General: Foxtail Flats is a 170-MW solar energy project, paired with 80 MW/320 MWh of battery energy storage. The project will be located on the Ute Mountain Ute Reservation and private land about 10 miles northwest of Farmington, NM. The project will interconnect to an existing substation at DESRI’s San Juan Solar 1 project roughly 5 miles to the southwest of Foxtail Flats, which is connected to the electric grid at the retired San Juan Generating Station substation by an existing generation transmission line. Foxtail Flats Solar will provide significant benefits, including:

Supplying over half of Los Alamos County's and Los Alamos National Laboratory's electrical load with clean, low-cost energy
Helping the Ute Mountain Ute Tribe meet the goals of their Climate Action Plan
Creating over 200 construction jobs
Increasing the overall supply of clean, renewable energy on the grid

Planned start of construction and completion: Preliminary site prep (road work and final engineering studies) started in January 2026, with anticipated full mobilization in Q2 2026. Commercial operations are planned to begin in Q2 2027.

Project Status: The project has secured permits, site control, and executed long-lead procurement contracts. The project has awarded Engineering Procurement and Construction (EPC) firms for the entirety of the project scope and is developing construction-level engineering design.

This photo, taken from the site of Foxtail Flats on the Ute Mountain Ute Reservation, shows DESRI's San Juan Solar project in the foreground and the retired San Juan Generating Station in the distance.

How much power will this produce? Will it be enough?

This project will produce 170 MW during clear sunny daylight hours, which is more than enough to supply the 90 MW peak daytime load for the Los Alamos Power Pool (LAPP), which is the partnership that meets the combined energy needs and resources for Los Alamos County (LAC) and Los Alamos National Laboratory (LANL). DPU will also supply Sandia National Laboratory and Kirtland Air Force Base (Sandia/Kirtland) with 30 MW of power, charge the Battery Energy Storage System (BESS) with solar power, and sell any excess solar power.

How much energy will the battery store? How long will it provide power if used?

The BESS will provide a maximum power capacity of 80 MW continuously for 4 hours, with a total energy capacity of 320 MWh.

Isn't this an expensive source of energy?

The daytime power is relatively inexpensive at $37.88/MW for the entire 20-year term of the project. That being said, the BESS is more costly due to lack of storage technology. The blended cost for the combined resource is about $74/MW, which is a little bit less than long-term market power purchase agreements at the time the solar and storage agreements were signed.

When will we start receiving power from Foxtail Flats?

The planned full operational capability is June 2027.

With the solar field being in the Four Corners area, how will we get this power?

Power will flow from into PNM's San Juan 345kilovolt (kV) substation and transmission linesto reach Los Alamos County.

Why do we need a battery?

The battery will serve two purposes:It will help to supply night load of up to 320 MWh for LAPP and Sandia/Kirtland;Itwill storesome or allexcess solar power,lowering the need to sell excess solar power.

What happens when we enter a stormy period without much solar production?

Our day-ahead and real-time scheduling desk will purchase power from suppliers to make up the difference. This is already a regular operational task under DPU's Electric Production division, not an unusual circumstance resulting from the project.