Power abberations (dirty power) are a localized phenom, dependent on age of utility infrastructure, profile of other users on your piece of the grid, condition of your residence (design of home wiring/age of appliances), etc.
My former place was a 50 year old house with a rats nest of wiring and noticed no difference going off the grid. My current place (new build with underground service, our own transformer, all new appliances, dedicated audio circuits, separate grounding, and cryo'd hospital grade receptacles) as you might guess also showed no difference.
Some swear by battery power, others swear at it (as a waste of money/effort).