Pull the breakers and look for heat on the bus bars. That sounds like a arc creating resistance.

The fluctuation doesn't coincide with anything else coming on. When it happens it always changes minutes apart but like I said it doesn't do it all the time.

you also just described lightning.

It does happens sporadically every day.

Ten volts is a pretty substantial swing. Neglecting other sources of resistance in the circuit and calculating on the cable resistance only, on a 20 amp circuit (awg 12 wire) 100' from the panel, a 10 volt increase would require that a 60 amp load on the same circuit were suddenly removed. That's not too likely (we hope).

This suggests a high resistance connection somewhere in your circuit. That would be a real hazard, because it could heat up and start a fire.

The fact that you see voltage spiking to 125 volts, well above the mains nominal, makes me suspect a loose or improperly made (high-resistance) neutral connection.

The typical symptom of a high resistance neutral is that some lights brighten as others dim. You may not always notice this "complementary" effect because the dimming lights and brightening lights may not be in the same room.

A house-wide effect usually means that the neutral connection is loose or corroded at the main panel. I've even heard of neutral problems outside the house causing this.

If you're sure this is happening only in the bedroom, you should investigate whether your fans might be plugged into a multiwire (shared neutral) circuit. If so, all neutral connections on that circuit should be checked. A poorly applied wirenut in the neutral can cause this.

In any case, it's a good idea to have a pro check this out.

Please let us know what you find.

Possibly something related to the problem at a friends house. The Maytag traditional topload washer would not spin with a load of wet laundry but would without clothing. Got another washer, luckily a free Maytag, but same condition. After finding voltage differences high and low as you have noted at a number of outlets throughout the house we called the power company as I had heard a heavy power draw in a residential area, such as an illegal marijuana grow operation or heavy machinery could cause low voltage, they came out and found a tree branch was pulling on the overhead power line to the house- they re-routed a new power line, problem solved! I hope your issue can be as easily resolved-don't buy new fans just yet!

That sounds like an intermittent heavy load on one half of the pole transformer that is unbalancing it. The pole transformer is the one outside on the pole and may be feeding up to 5 houses or buildings. It is fed by the local power lines. (If you have underground electrical distribution, this transformer may be a locked cabinet.)

For example, running an electric arc welder off one side of this transformer has been known to cause voltage unbalance on the 2 halves of the transformer's output windings.

The output side of this transformer is a single, center tapped winding. The center tap may be grounded. (For illustration purposes, I'll be using 120V although the actual voltage might be 105 to 120 V.) The voltage from one end of the winding to the center tap 120 V and the voltage from the center tap to the other end of the other end of the winding is also 120 V. The voltage across the outer ends of the winding is 240 V. However, note that either end of the transformer is only 120 V with respect to ground (center tap).

A property of the transformer is to try to maintain a constant voltage from end to end of the output winding. A load that is much greater on one half of the winding than the other half does this: An out-sized load on one half of the winding will cause the output voltage to drop in that half; The voltage rises in the other unloaded winding such that the total voltage remains at 240 volts, i.e., One half may drop 5 volts while the other half increases 5 volts.

Can that effect be countered at the home with additional equipment?