As more wind and solar power are added to the electricity grid, keeping the supply and demand balanced becomes more challenging.
Traditional methods rely on power plants adjusting their output, but a new study suggests that home air conditioning units (ACs) can help stabilize the grid without homeowners noticing any difference in comfort.
Researchers from the University of Michigan partnered with Pecan Street Inc. to test this idea in real homes in Austin, Texas.
Their study, published in IEEE Transactions on Smart Grid, found that residential AC units can act as a reliable tool to regulate the power grid—all while keeping homes cool.
How can AC units help the grid?
Electricity must always run at 60 Hz frequency to keep the grid stable. Traditionally, power plants adjust their output to maintain this balance.
However, home AC units naturally cycle on and off to keep indoor temperatures steady.
By slightly shifting the timing of these cycles across many homes, ACs can collectively adjust energy consumption and help bring the frequency back to 60 Hz.
Johanna Mathieu, associate professor at U-M, said, “Residential air conditioners can provide high-value grid balancing services without affecting homeowners. This resource is already available—we just need to use it.”
Most previous research on using flexible energy loads for grid balancing was done through computer simulations. To test it in real homes, the U-M team recruited 100 homeowners in Austin to participate in four one-hour experiments.
A challenge they faced was that smart thermostats do not allow third-party control of AC units. To get around this, researchers installed custom hardware in each home, allowing a central control system to adjust AC operations in real time through the cloud.
The system worked: it successfully adjusted AC usage every 2 seconds to match grid needs. Even better, home comfort was not affected—the average indoor temperature only changed by 1.6°F at most.
A scalable future solution
The study showed that AC units can be used on a large scale to balance the grid, but there are still hurdles to overcome. Installing custom hardware in every home is not practical. Instead, researchers suggest that smart thermostat companies allow third-party control to make the system easier to implement nationwide.
With the right technology in place, this simple, cost-effective solution could help improve grid reliability, support renewable energy, and reduce the need for power plant adjustments, all without homeowners noticing a difference in their daily lives.
