The 58.6-megawatt battery complex Axpo and Energie Uri inaugurated in Gurtnellen this week is described as Switzerland’s largest battery storage facility to date. A single existing Swiss pumped hydro plant, Nant de Drance in Valais, has a power rating of 900 megawatts and an energy capacity of 20 gigawatt-hours, roughly 18 times the power and 200 times the storage capacity of the new project combined.
Axpo’s 50-megawatt, 100-megawatt-hour battery and Energie Uri’s smaller system, reported at 8.6 megawatts when construction began last September and at 8.4 megawatts in this week’s commissioning announcement, sit on adjoining plots in Gurtnellen’s Platti industrial area in the canton of Uri. Fluence supplied the battery technology for both systems, while Axpo’s grid subsidiary CKW handled installation and interconnection. Construction took just under a year, and Axpo has said the facility will primarily serve national market functions such as frequency regulation, while Energie Uri’s smaller system is oriented toward the canton’s own grid needs. Both descriptions point to genuine, useful grid services, but the “largest to date” framing invites a scale comparison the announcement itself does not offer.
Switzerland’s existing pumped hydro storage capacity totals roughly 3,503 megawatts, according to the Swiss Federal Office of Energy, meaning the new Gurtnellen batteries add less than 2% to the country’s installed flexible storage power capacity even before accounting for the country’s much larger base of conventional storage hydropower, an additional 8,124 megawatts that, while not built for rapid charge and discharge cycling in the way pumped storage or batteries are, still provides substantial dispatchable flexibility. The single-plant comparison is more direct. Nant de Drance, a pumped storage facility built into a cavern 600 meters underground in Valais and completed after 14 years of construction at a cost of 2.2 billion Swiss francs, went into commercial operation in 2022 with six 150-megawatt turbines for a combined 900 megawatts of power and 20 gigawatt-hours of storage drawn from its upper reservoir. That single facility outweighs Gurtnellen’s combined battery capacity by a wide margin on both the power and energy dimensions, a reminder that “largest battery storage facility” is a narrower claim than it may initially read, specific to one storage technology within a national grid where that technology remains a minor contributor next to hydropower.
The rationale for building battery capacity in a country this well endowed with pumped storage rests on a genuine technical distinction rather than a redundant investment. Pumped hydro projects like Nant de Drance require specific alpine topography, large elevation differences between upper and lower reservoirs, and construction timelines measured in over a decade, along with capital costs in the billions of francs and extensive environmental mitigation; Nant de Drance’s developers spent 22 million francs on 14 environmental offset projects alongside the plant itself. Batteries, by contrast, can be sited close to substations and load centers with far less dependence on terrain, and Gurtnellen’s construction timeline of under a year reflects that flexibility. Batteries also respond within milliseconds to grid frequency deviations, a service pumped storage can provide but typically with slower ramp characteristics tied to turbine and penstock hydraulics, which is why Axpo has positioned the Gurtnellen facility specifically around flexible, fast-responding grid services rather than as additional bulk energy storage competing with the country’s hydro reservoirs on capacity alone.
Axpo’s own public communications have described the 100 megawatt-hour Axpo facility in two different ways: as equivalent to the annual electricity consumption of 22 four-person households in one company publication, and as covering the daily needs of more than 10,000 households in another. The two figures are not actually contradictory; they describe the same 100 megawatt-hour quantity distributed across different timeframes, but the fact that Axpo has used both framings in separate materials illustrates how a modest absolute quantity of storage can be presented at very different scales of apparent significance depending on which reference period is chosen. The company’s broader European ambitions have shown similar variation over time: when the project was announced in September 2025, Axpo said it planned several hundred megawatts of storage within three years across Germany, Spain, France, Italy and Poland; the company’s more recent characterization of its European pipeline substitutes Romania for Spain among the countries with projects under construction, a shift that suggests the specific project list remains actively evolving rather than fixed since the original announcement. Against Axpo’s own prior Swiss deployment, a 2-megawatt, 2.17 megawatt-hour pilot system at Jona-Rapperswil, the Gurtnellen facility represents a genuine step up in scale for the company’s domestic battery business, even though it remains a small fraction of the storage capacity Switzerland has already built into its mountains over the past several decades.
