The hybrid advantage: Why flywheel-battery systems are grid stability’s best-kept secret

There's a quiet revolution happening in American energy infrastructure, and it's unfolding in places you might not expect.

This fall, students at a K–12 school in Sandy, Utah, will watch the grid of the future operate in real time. Outside the Murray Science Center at Waterford School, a hybrid flywheel-battery storage system powers operations, smooths geothermal loads, and gives students hands-on exposure to the technologies they'll inherit.

That same architecture—high-speed flywheels paired with lithium iron phosphate batteries—now supports commercial deployments built to participate in utility demand response programs while withstanding extreme weather and grid stress. This educational demonstration is a scalable model for distributed infrastructure that delivers speed, resilience, and real value to utilities and commercial operators.

The takeaway is clear: smarter storage is already here.

The battery degradation reality

Ask any utility engineer about frequency regulation duty cycles, and you'll hear the same story: batteries degrade quickly under constant cycling. The field is littered with early replacements, derailed economics, and procurement teams hesitant to greenlight large-scale deployments.

Several proposed large-scale battery projects in the U.S. have been shelved due to cost, complexity, and supply chain volatility. Meanwhile, coal plants stay online to serve data center load, simply because current storage options don't hold up economically over the long haul.

This isn't a failure of technology. It's a mismatch of application. Batteries excel at energy storage. They're poorly suited for high-frequency power management.

Flywheels are the opposite: not ideal for long-duration storage, but unmatched for fast response and power quality.

Pair them wisely, and both technologies thrive.

How hybrid systems work

The concept is simple: flywheels absorb the stress that kills batteries, like voltage spikes, frequency swings, and rapid cycling. Batteries handle the longer-duration storage and smooth discharge they're designed for.

At Waterford, the science center draws from 45 on-site geothermal wells. While geothermal may sound steady, the electrical load varies constantly as HVAC systems cycle. A conventional battery system would wear out quickly. The flywheel smooths those fluctuations while the battery array provides backup power and multi-hour storage.

Students watch frequency regulation and voltage control in real time. The building teaches grid operations better than any textbook.

American manufacturing gets serious

For hybrid systems to scale, we need a reliable domestic supply chain. Domestic battery manufacturing is finally becoming competitive. New American-made LFP cells now deliver 3–6C performance, rivaling the world's best. These cells are engineered for demanding grid applications, built domestically, and designed for recyclability.

Pair them with flywheel technology, and you get hybrid systems that can manage temperature extremes, meet uptime requirements, and support grid services like demand response, peak shaving, and ancillary reserves without compromising asset life.

No supply chain anxiety. No geopolitical risk. No performance tradeoff.

Data centers and EV charging: New pressure points

Load growth from AI data centers and EV fast-charging is already overwhelming planning models.

Hybrid systems offer a better equation. Flywheels provide clean ride-through power during grid disturbances, which is critical for AI workloads that can’t tolerate even millisecond-level interruptions. Batteries step in for longer outages and shifting loads.

At charging stations and commercial and industrial sites, flywheels absorb sharp demand spikes while batteries sustain the power output needed to serve multiple EVs or high-draw machinery.

The result: infrastructure that avoids costly grid upgrades and remains responsive under pressure.

The real economics

In many situations, flywheels cost more upfront. But over 20 years, they deliver lower total cost of ownership with no degradation, no replacements, and minimal maintenance.

More importantly, they extend the life of battery systems. Instead of replacing degraded cells every 8–10 years, utilities can operate systems reliably for 15–20.

That math matters when the U.S. grid faces $1.1 trillion in capital needs over the next decade.

Moving beyond demonstrations

Commercial hybrid projects are operating and domestic manufacturing is scaling.

What's catching up is recognition. Hybrid systems solve challenges that single-technology approaches can't. Batteries alone degrade under high-cycling stress. Flywheels alone don't provide enough stored energy.

Together, they create something new: a storage platform that gets stronger under stress, not weaker.

The path forward

The grid America needs won't run on any single technology. It will depend on systems that combine mechanical durability, chemical efficiency, and intelligent control from the edge of the grid to the core.

Waterford shows that this model works. Commercial deployments prove it scales. American manufacturing makes it viable.

The challenge now is recognizing where hybrid systems fit and scaling them intelligently.