I have a customer in a downtown area that has potential power issues. We have run an analysis internally (input power on UPS's in the server room) and externally (power company). The graphs on what is reach us match the graphs from the outside of the meters, so we do not have an issue within the building. Our power fluctuates between 125V to 130V, sometimes hovering around 129V for 2-3 hours.
All the equipment in the server room is protected by Line filtering UPS's, so I am not overly concerned about that room. My concern is everything else.... computers, printers, copiers, scanners, etc.
The power company and the electrical contractor stated that the constant fluctuation and power levels are "normal". The power company stated that they consider plus or minus 10% acceptable. So on a 120V, they are happy with 108V-132V. I honestly do not know enough about the tolerances of computer equipment to know if this will cause an issue.
I am asking this because the electricians have told us that they can install an isolated transformer on our side of the power meters that will level out the voltage being delivered to our office space. I am assuming this is basically a line filter to get rid of the spikes and provide us a solid 120V. Such a device does not come cheap.
So my question is "How much is too much"? How much fluctuation. How much voltage. At what point do we concern ourselves with the damage (if any) being done to our equipment.