Hi,
The boost on the Sola Basic has three "switch points"
at 110 it boosts approximately 10%
At 100 it boosts approximately 20%
at 90 it boosts approximately 30%
The buck is listed to come on at 134 volts. I am not able to test for voltage that high and have never encountered it "in the wild".
I have used the Sola on a 94 volt (under load) 15 amp shore power plug to run the roof air conditioner. The amperage did eventually cause the shore power breaker to trip after about 2 hours. At that point I switched the fridge to gas and was able to continue to use the roof air.
Wattage demand on the roof air conditioners does change. Mine goes from about 1300 to over 1900 watts as the ambient temperature goes up.