I have three 16-1/2" basic 90's-vintage lava lamps, and I run them about 10 hours, during the day. My husband is complaining that it's causing our electric bill to go way up, and I say it's going up because it's winter. So......can anybody tell me just how heavy the hit is from a lava lamp. The lamps do get very hot, which kind of scares me, but it's only a 40 watt bulb, after all. Can someone give me info? Thank.