Yes, there can be voltage variations that result in fluctuations in radiation virtually all light sources, including UV fluorescent tubes. This can vary a lot depending on house wiring, applicances on the circuit, and time of day, but in many cases the cumulated variation is more than sufficient to affect exposure. The best solution for this is to place a light integration system on your exposing unit. All platemakers, Nuarc 26-1k for example, have this feature.
Originally Posted by mikepry