Planet Rock Energy Storage

Project introduction

On the hottest afternoons in Pueblo County, air conditioners across the region pull hard on a grid that has to match that demand instantly, often turning to the most expensive generation available to keep up. Planet Rock Energy Storage is being developed to change that math. The project will store power when it's cheap and abundant, then release it during the hours the grid strains hardest.

Located a mile north of the Tundra Substation in rural Pueblo County, Colorado, Planet Rock pairs 1,500 MW of lithium-ion batteries built for four-hour response with 50 MW of iron-air batteries built for longer-duration discharge, for a combined 1,550 MW. Together, the two technologies cover a wider range of grid needs than either could handle alone.

The project is currently in development, with construction planned in phases. The first 550 MW of capacity is scheduled to begin operating in 2029, with the remaining capacity following in later phases. The 180-acre site sits in a sparsely populated stretch of the county. Its closest neighbors are an existing NextEra solar project and an Army depot, not residential subdivisions. That rural setting, paired with its proximity to the substation and transmission lines it needs to reach the grid, is part of what drew RWE to the location.

Status: In development

Site location

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Facts and Figures

00 MW

total capacity once the project is fully built out

00 MW

Amount of megawatts the battery storage aspect of the project will hold.

RWE ranks number 00

in the United States for solar energy with over 6 gigawatts.

00 Acres

making up the project's total footprint

Project Benefits

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Backup Power When It Counts

Grid operators have one job that never stops: matching electricity supply to demand, second by second, as that demand shifts throughout the day. Battery storage gives them a tool that can respond instantly, which is exactly what's needed when a storm knocks out a transmission line or a heat wave pushes air conditioners into overdrive. Planet Rock's location, a mile from the Tundra Substation, means the power it stores can reach the local grid quickly. Paired with the wind and solar generation already operating in the region, the project adds a layer of backup that helps keep outages short and rare.

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Smoothing Out Price Spikes

Electricity prices have climbed faster than inflation in much of the country, even as demand keeps rising. Planet Rock is built to store power when it's cheap and abundant, then release it during the hours when demand peaks and the most expensive generation on the grid would otherwise kick in. That timing matters: by displacing costlier resources during peak hours, battery storage helps flatten the price curve for everyone on the grid, not just the utility. For a region facing hotter summers and growing demand from manufacturing and data centers, that kind of price stability adds up over the life of the project.

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Built and Monitored for Safety

RWE has spent more than a decade building, operating, and maintaining battery storage projects across the country, and safety sits at the center of that track record. Planet Rock's batteries will sit in enclosures spaced evenly across the site, a design choice that limits how a single issue could spread. The site will run under 24/7 remote monitoring, and the iron-air batteries included in the project carry a lower fire risk than some other battery chemistries. Battery technology is well understood and heavily regulated, and RWE holds itself to those standards at every project it builds, including this one.

Stronger Electric Grid

A row of white storage containers lined up on a gravel surface, with power poles in the background against a clear blue sky.
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Connecting to the Regional Grid

Planet Rock will connect to the Western Electricity Coordinating Council, the organization responsible for grid reliability across the western United States, through the Tundra Substation just a mile from the project site. Unlike wind or solar generation, battery storage is dispatchable: it can deliver power on demand rather than only when conditions allow. That firm capacity supports the region's broader energy security, where a more reliable, homegrown power supply lowers the odds of outages and price spikes when demand runs high.

For a typical household, that shows up in small but real ways: fewer outages during the hottest days of summer, steadier prices when demand spikes, and less reliance on power imported from neighboring states. It also gives local manufacturers and other large electricity users more confidence that the power they need will be there when they need it. Planet Rock is designed to be part of that dependable supply for decades to come.

A Rural Corner of Pueblo County Doing Its Part for a Growing Grid

Twenty years from now, the stretch of land a mile north of the Tundra Substation will likely look much as it does today: quiet, rural, and shared with an existing NextEra solar project and an Army depot. What will have changed is what's running underneath that quiet. Planet Rock's batteries will have spent years storing power during calm hours and releasing it during the moments Colorado's grid needs it most, the July afternoon when every air conditioner in the region turns on at once, or the January cold snap that pushes heating demand to its peak.

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That kind of flexibility becomes more valuable every year. Colorado's electricity demand is climbing as data centers expand, manufacturers grow their operations, and more households and businesses electrify. Meeting that demand takes more than any single energy source can offer, and battery storage gives the grid a way to bank power when it's plentiful and spend it when it's scarce. Planet Rock adds 1,550 MW of that flexibility using two battery technologies built for different jobs: fast four-hour response and longer-duration backup.

For the residents who live near the project, the payoff is straightforward: a more reliable grid, fewer disruptions during extreme weather, and a project built with safety and rural land use in mind from the start. RWE plans to keep talking with the community as Planet Rock moves through development, starting with a public meeting this August, because a project built to serve the grid for decades should also serve the people who live closest to it.

Will there be a solar project near the battery storage site?

No. Planet Rock Energy Storage is a battery storage project only. It stores power rather than generating it. The nearest solar generation is a separate, existing project operated by NextEra, located near the site but not part of Planet Rock.

Is battery storage safe?

Battery storage is a mature, heavily regulated technology, and RWE has built, operated, and maintained BESS projects for more than a decade. Planet Rock's batteries will sit in enclosures spaced across the site and will be monitored remotely around the clock. The project also includes iron-air batteries, a technology with a lower fire risk than some other battery chemistries.

When will construction start, and when will the project be operating?

Planet Rock is currently in development. The first 550 MW of capacity is scheduled to begin operating in 2029, with remaining capacity following in later phases. RWE will share more specific construction timelines as permitting and planning move forward.

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