I watched a film about 20 years ago and it traumatised me for a while (I was 6). I only remember very small parts of it but it was basically some kind of slug monster that killed people (Think tremors + Jaba the hutt but with a wide mouth thing). Possibly killed things with electricity.
Anyways, I believe that the monster is defeated maybe at an electricity power station in the end?
I also remember a scene where a guy was killed in his bed, possibly electrocuted. It could have been an episode of a show rather than a film, in which case I apologise.
If you manage to identify it, you are brilliant!