This is not really an issue. Usually you have 4-5 seconds to react for the "hot reserve". Also for the known peaks you can preventively switch off the loads (it

This is not really an issue. Usually you have 4-5 seconds to react for the "hot reserve". Also for the known peaks you can preventively switch off the loads (it is amazing what happens at 7:02am when everybody switches on their kettle at the same time, even worse with water supply and flushing peaks). In addition such systems sometimes measure frequency deviation and switch off/on the load when it goes out of bounds. The result is that this works really well for fast balancing as soon as you have few hundred installed spots in one grid. And there is real money in it with ROI 1..3 years for the service provider. Disclaimer: my electronics engineering company has worked with research, design and engineering of such load balancing hardware