RWE secures Tesla battery supply and Colorado utility offtake deal for 200MW standalone BESS

Prior to the CUP application, RWE Clean Energy held an informal open house meeting in May of this year giving the local community an opportunity to learn about the project. The developer also gave a formal presentation of its plans for the project during a virtual meeting held in July 2024.

120 Tesla 2XL Megapack BESS units

The South Park project is a 200MW standalone BESS located on a 36-acre plot of land approximately six miles north of Hartsel, west and adjacent to Highway 9 in Park County, Colorado.

RWE’s CUP application with Park County reveals that the project will be made up of 120 Tesla lithium-ion 2XL Megapacks covering 6.19 acres of the proposed site.

Tesla’s second-generation Megapack, which has integrated power conversion system (PCS) equipment, is a popular battery system choice for developers and utility’s throughout the US, including Engie and Georgia Power as covered in recent ESN Premium articles.

The popularity of this battery technology doesn’t come as a surprise, with the new Battery StorageTech Bankability Ratings report from our colleagues at PV Tech Research revealing Tesla to be the only AAA-Rated supplier from the industry Top 15 identified.

Colorado utility, coop to take joint ownership of project

South Park BESS is expected to connect to the local electricity grid through the Hartsel 230kV substation, jointly owned by CORE Electric Cooperative and Xcel Energy, via an approximately 0.33-mile transmission line.

The recent CUP application also reveals that upon successful completion of the BESS, RWE will transfer ownership of South Park BESS to Xcel Energy subsidiary Public Service Company of Colorado (PSCo), who will manage and operate the project.

This suggests that the two parties may have negotiated some form of Build-Transfer-Agreement (BTA) for the project, although further details weren’t provided within the CUP application.

If the CUP is approved, South Park BESS will form part of Xcel Energy’s long-term mission to reduce carbon emissions and aid its transition to a cleaner energy portfolio, known as its Clean Energy Plan. As well as pledging to end coal usage by 2030, the plan also aims to add 600MW of storage capacity to the utility’s portfolio also by the end of the decade, as reported in Energy-Storage.news.  

Construction on the project is expected to commence during the summer of 2026 with commercial operation scheduled for the end of 2027.

Energy storage in Colorado

Despite not being as widely reported as other markets in the US, independent power producers (IPPs) are quietly filing permits to construct utility-scale renewable projects incorporating energy storage throughout Colorado.

RWE’s South Park BESS project is one of a handful which the developer is proposing for Colorado, that also includes a 250MW solar farm co-located with a 1,000MWh BESS known as the Trapper Solar project located in Routt County. Officials at Routt County are currently reviewing a Special Use Permit (SUP) for the Trapper project after RWE submitted the application in June 2024. 

The Tundra A project, comprising 130MW of solar generation with a 50MW BESS, is another Colorado project under development by RWE in Pueblo County.

However, other IPPs have begun to highlight their Colorado developments, such as AES Corporation, which has launched a webpage dedicated to their renewable proposals in the state. Although the Arlington, Virginia-headquartered IPP currently has no operational BESS facilities in the state, it’s proposing to construct over 1GW of BESS capacity across seven different projects according to the company’s website.

RWE’s presence in the US

In 2023, RWE bolstered its US presence through the acquisition of former Con Edison subsidiary Con Edison Clean Energy Business, along with the company’s 3.1GW portfolio of renewable assets, for US$4.1 billion. Following the acquisition, RWE consolidated its US solar, wind and storage activities to form RWE Clean Energy.

According to the company’s most recent annual report, RWE’s US subsidiary had renewable assets totalling 9.2GW at the end of 2023.

This portfolio includes three battery storage projects totalling 900MWh of capacity connecting to the Electric Reliability Council of Texas (ERCOT)-owned grid that recently broke ground, as reported in Energy-Storage.news.