Hi,
I recently had a chance to test my Sola Basic autoformer right down to 96 volts. Even at that low a voltage the boost was enough to allow me to safely run my roof air conditioner. It was a weak 15 amp circuit at a rural Church, so I chose to only run the roof air.
I chose an autoformer because my comfort zone for voltage is no lower than 107. None of the current crop of EMS devices will deal with that.
The Hughes autoformer offers the same surge protection as the PI unit, does check for bad wiring and solves the low voltage issue, too.