They told you that you have " Dirty " electric? Har, har, he, he, har!!! Sorry to say, but there is no such thing! You either have electric or you don't! If there is 110 volts there, then it will work. " Dirty Electric", what will they come up with next?? Har, he, he har.
Absolutely there is. I used to be a electrical engineer long time ago and electrical noice problems in the home is nothing new. It comes from all kinds of problems. You can trace it down to one appliance even. Take a occilliscope and put it on freerun and take a look at the noise yourself.
It gets worse as you go out to real sandy areas, where a good ground to sink the noise is hard to find. Noise on the line is the reason we had to put a sprinkler or water trickler out in Regenerator's for fiber optic systems with the grounding rod when I worked for LCI and MCI out in Reno, NV.
These scales consist of transducers that work in mA and uA electric currents. Especially something as small as a grain. Opening the window, drafts, dryer running with the same circuit as the scale all have an effect. Something as noisy power line has no effect on your radios or TV or computer that could care less about .1V changes, but some items do. They can isolate this, and I am not sure why they don't with some high Freq filtering, or capacitance circitry. I guess cost too much.