Many growers use aeroponics for their main system and rely on hydroponics as a backup. It wouldn't make sense to try to combine them on a daily basis because their methods oppose each other. Hydroponics operates by keeping roots submerged in water all or most of the time, while aeroponics operates by suspending roots in air and misting them at specific intervals. Since roots can be both submerged and suspended in the air, they can't be combined simultaneously.
Aeroponics growers who are concerned about power failures or equipment problems - typically large commercial growers - may set up nutrient channels or reservoirs and a system that allows the plants to be temporarily lowered into them. This can carry vulnerable plants through a short period without risk of drying out ,but even hydroponics systems rely on electricity to keep the water flowing, and the plants will suffer when oxygen and nearby nutrients are depleted. The complexity, extra structural elements, and space required also make this a difficult system to justify compared to a generator, for example.
