Mechanical energy storage market: size, technologies and outlook to 2035

Why mechanical energy storage is moving into focus

Grids built on solar and wind need somewhere to put power when the sun sets and the wind drops. Lithium-ion batteries answer part of that question, but not all of it — they degrade, they carry fire risk, and their supply chains sit largely outside the West. That gap is why the mechanical energy storage market is drawing fresh capital and attention. Instead of chemistry, these systems hold energy as motion, height or pressure, and many of them run for decades without losing capacity. The sections below follow one thread: mechanical storage competes not on headline price alone, but on lifetime, safety and how many cycles it can deliver.

• Definition and physical principle, set against electrochemical storage
• Current market size and the forecast path to 2035
• The four leading technologies compared on efficiency and maturity
• Growth drivers, applications, regions and the barriers ahead

What is mechanical energy storage?

Mechanical energy storage captures electrical energy by converting it into a physical form — the motion of a spinning rotor, water lifted to a higher reservoir, or air compressed into a cavern — and releases it later by reversing that process. The physics is simple; the engineering is not. High-strength materials, magnetic bearings and precise control systems make these forces usable at grid scale. The key distinction from lithium-ion or flow batteries: no chemical reaction stores the energy, so there is no electrochemical degradation and, in most designs, no thermal runaway. This makes mechanical systems attractive wherever long life, safety and heavy cycling matter more than compact size.

• Kinetic storage (flywheel): a rotor spins in a near-frictionless, often vacuum-sealed chamber and returns energy through a motor-generator.
• Gravitational storage: water or solid weights are raised when power is cheap and dropped to drive turbines on demand.
• Compressed air (CAES): ambient air is compressed and stored underground, then heated and expanded through a turbine.
• Distinction from electrochemistry: no lithium, cobalt or liquid electrolyte — energy is held physically, not in chemical bonds.
• Typical strengths: long calendar life, high cycle counts, fast response and negligible environmental impact.

How big is the market and how fast is it growing?

Grid-scale storage has moved from a niche technology into core power-system infrastructure, and the market data reflect that shift. The overall energy storage market, across all technologies, is on track to reach about $226 billion by 2035 at a compound annual growth rate near 21 percent (Market Research Future). Within that total, long-duration storage is the segment most exposed to the renewables build-out. Independent forecasts place the long-duration energy storage market at roughly $4.8 billion in 2024, reaching about $10 billion by 2030 and $17 billion by the mid-2030s at a compound annual growth rate near 14 percent (MarketsandMarkets; SNS Insider; Polaris Market Research). Mechanical storage, which spans pumped hydro, compressed air, gravity systems, and flywheels, forms the backbone of grid-scale long-duration capacity (Global Market Insights).

The dollar forecasts understate the physical requirement behind them. Modeling by McKinsey & Company for the Long Duration Energy Storage Council concludes that reaching net-zero power grids calls for 1.5 to 2.5 terawatts of long-duration storage globally by 2040, equal to 8 to 15 times the storage capacity installed today, or 85 to 140 terawatt-hours of energy capacity, at a cumulative investment of $1.5 trillion to $3 trillion. That timeline is being compressed by the accelerating substitution of renewables for fossil generation and by a step-change in electricity demand from AI data centers, whose load transients are now a recognized grid-stability concern.

Key figures:

• Overall energy storage market: about $226 billion by 2035 at a CAGR near 21 percent, all technologies (Market Research Future).
• Long-duration storage, Qnetic’s addressable market: roughly $4.8 billion in 2024, reaching $10 billion by 2030 and $17 billion by the mid-2030s at a CAGR near 14 percent (MarketsandMarkets; SNS Insider; Polaris Market Research).
• Structural requirement: 1.5 to 2.5 TW of long-duration storage needed globally by 2040, 8 to 15 times today’s installed capacity, at $1.5 trillion to $3 trillion of investment (McKinsey / LDES Council).
• Technology position: mechanical storage is the backbone of grid-scale long-duration capacity, the category in which Qnetic’s flywheel competes directly against batteries and pumped hydro (Global Market Insights).
• Demand driver: long-duration storage of eight hours and beyond is shifting from optional to required as renewable penetration and AI data-center load rise together.
• Investment signal: capital is flowing across the long-duration landscape, spanning pumped hydro, flywheel, gravity, and flow-battery projects.

Which technologies shape the mechanical energy storage market?

Four technologies carry most of the market, and they are not interchangeable. Thermal and pumped-heat systems, which some market reports file under the same heading, store energy as heat rather than as motion, height or pressure — they sit outside the definition used here. Pumped hydro provides the bulk of installed capacity worldwide but depends heavily on geography. Compressed air scales to large reserves yet suffers lower round-trip efficiency. Flywheels respond in milliseconds and cycle almost endlessly, historically at short durations. Gravity-based systems are newer and still proving themselves at scale. The table sets them side by side on efficiency, duration and maturity — and includes Qnetic’s grid-scale flywheel, which pushes kinetic storage from seconds into the multi-hour, long-duration range that the market increasingly demands.

Qnetic’s system reflects where the market is heading: a carbon-fiber rotor on magnetic bearings in a vacuum chamber, designed for 1 MWh per unit, rugged duty-cycling and a 30-year service life – engineering targets for a platform still moving from prototype to pilot, not specifications of a delivered product.

What is driving market growth?

Several forces push demand at once, none of them dominant on its own.

Qnetic tracks these drivers closely: regulatory pushes such as Virginia’s SB 448, which targets 4.5 GW of long-duration storage, and the surge in AI data-center load are exactly the conditions its flywheel platform is engineered to serve.

Where are mechanical storage systems used today?

The drivers above translate into concrete duties on the grid, from sub-second response to multi-hour shifting.

Qnetic’s platform sits at the long-duration end of this list: units combine into arrays of any size — a 40 MWh / 10 MW block covers roughly 10,000 US households for four hours — and each unit still answers a grid signal in under three milliseconds.

Mechanical storage or battery storage (BESS): what pays off?

Here sits the question most comparisons skip. Lithium-ion BESS often wins on upfront capex and energy density, so buyers assume it wins overall. The lifetime picture is different. Batteries degrade, are frequently limited to one cycle per day, and typically last 7 to 10 years. Mechanical systems – flywheels in particular – cycle heavily without wearing out and run for decades, which changes how much energy they can trade over their life. That is why cost per MW alone misleads: the right metric is levelised cost of storage across the whole life. A 1 MW / 4 MWh BESS lands at roughly 125 to 334 USD per kWh installed – some 0.5 to 1.3 million USD for those four megawatt-hours, with NREL’s 2025 benchmark at the upper end and the most competitive projects at the lower – and its replacement cycle and cycle limits reshape the total from there.

Qnetic’s LCOS analysis, produced with Dr. Oliver Schmidt and Dr. Iain Staffell of Imperial College London, makes the point plainly: with zero degradation and unlimited multi-cycling, the platform is projected to trade up to 3.4 times more energy over its lifetime, so a similar capex converts into far more revenue than a comparable battery. The 56 USD/MWh figure is a modelled 2030 target for a 100 MW, four-hour project, not measured plant data.

Which regions and providers lead the market?

Geography still decides much of this market, both for demand and for the incumbents supplying it.

• North America: the largest market, led by the United States with heavy grid investment and strong battery-storage leadership.
• Asia-Pacific: the fastest-growing region, driven by rapid renewable build-out and manufacturing scale.
• Europe: policy pull from the European Green Deal and national decarbonisation targets in France, Italy, the UK and Germany; the segment there is set to pass 2 billion USD by 2032.
• Established suppliers: market studies repeatedly list ABB, Siemens, Toshiba, General Electric, Schneider Electric, Fluence Energy and Energy Vault.
• Emerging challengers: deep-tech developers such as Qnetic push long-duration flywheels, backed by partners including ABB, SOSV, Imperial College London and EPRI.
• Reference projects: Qnetic works with SMUD, the independent power producer Arevon and Germany’s Bürgerwindpark Janneby to validate its technology.

Qnetic sits in the challenger group, targeting the US first – with a production center in Sacramento, California – before expanding toward the Middle East, Europe and Asia.

Which barriers slow the market until 2035?

Growth is not guaranteed, and the same market studies that project expansion also flag friction points.

• Location dependence: pumped hydro and CAES need specific geography, limiting where large projects can be built.
• High capital costs: upfront investment for grid-scale mechanical systems remains steep and slows adoption.
• Permitting and approvals: long licensing timelines and land-use questions delay reservoirs, caverns and large installations.
• Acceptance and awareness: newer technologies such as gravity and long-duration flywheels still need independent validation to win utility trust.
• Competition from cheap batteries: subsidised, China-dominated lithium-ion supply keeps price pressure high across the sector.
• Early technology risk: prototype-stage players face the classic scale-up challenge from demonstrator to series production.

Qnetic faces the last two barriers itself: the company is pre-revenue and prototype-driven, moving from the 20 kWh Vega and the 200 kWh Pulsar alpha unit toward EPRI-validated pilots with SMUD from 2027.

Our experience with mechanical energy storage at Qnetic

Qnetic’s commercial lead brings direct history with this technology class. “Early in my career, I worked on one of the world’s first efforts to commercialize flywheel energy storage. That experience gave me a deep appreciation for the technology’s unique strengths.” — Hugh McDermott, CCO & President Americas. That perspective shapes how Qnetic validates its work in the field rather than on paper.

How seriously Qnetic takes longevity is put plainly by Tod Stebbins, Director of Operations: “We’re not building for planned obsolescence. Every detail matters – because it still matters 30 years from now.” That standard shapes the company’s real project work, at one of it’s first planned pilots for example.

At National Lab of the Rockies Ares test bed campus, Qnetic will undergo the task of validating its grid-scale storage technology under a variety of use cases including matching wind, solar and AI data center operating profiles. The company has agreed to install and test prototypes at the site and to demonstrate energy time-shifting there. The agreement ties the technology to a specific, named grid site rather than to lab figures alone.

• 9.2 million USD raised — capital secured across multiple rounds since founding.
• 110 million USD / 460 MWh in signed LOIs — non-binding intent across 900+ units.
• 10,000 rpm reached — Vega prototype doubled its previously announced speed.

How Qnetic addresses the storage gap

Renewable grids need storage that lasts, cycles hard and never catches fire – the exact points where lithium-ion falls short. Qnetic answers that with a grid-scale kinetic battery: a carbon-fiber rotor on magnetic bearings, spinning in a vacuum, storing energy as motion instead of chemistry. It does what a battery does, mechanically, and keeps doing it for three decades.

• Zero degradation over 30 years — no capacity loss and no scheduled replacement costs.
• Unlimited daily multi-cycling — no one-cycle-per-day OEM limit, so the same unit can earn on the morning and the evening price peak.
• No lithium, no cobalt, no thermal runaway – solid-state metal, magnets and carbon fiber, intrinsically safe underground.

Qnetic is a pre-revenue, prototype-driven company with an openly high startup risk, currently moving from its Vega and Pulsar prototypes toward pilot deployments from 2027.

Conclusion: where the market is heading

The mechanical energy storage market is expanding on a clear logic: variable renewables and rising loads need storage that outlasts and out-cycles chemistry. The addressable long-duration market is already scaling toward $17 billion by the mid-2030s at close to 14 percent a year, and the dollar forecasts understate the physical requirement behind them. Modeling by McKinsey for the Long Duration Energy Storage Council puts the global need at 1.5 to 2.5 terawatts by 2040, roughly 8 to 15 times today’s installed storage, at $1.5 trillion to $3 trillion of investment. Mechanical storage forms the backbone of that capacity: pumped hydro anchors the installed base today, while flywheels, gravity systems, and compressed air extend storage into the longer durations and larger reserves the grid now needs.

For grid planners, the metric that decides a project is lifetime cost of service, and it favors non-degrading mechanical systems even where lithium-ion wins on upfront price. Across decades of cycling those systems hold their full capacity, and they carry none of the thermal-runaway risk of large lithium-ion installations. Barriers remain real: geography, capital cost, permitting, and early-stage risk. Within that landscape, Qnetic represents the direction of travel, moving flywheel storage out of short-burst duty and into the multi-hour, degradation-free range the grid increasingly requires. The underlying cost and load assumptions are published in two free reports: the LCOS analysis and the 26-page AI-Grade Energy Storage whitepaper.