So I came across this factoid and thought I would share and extrapolate. Based doubling the time in the attached graphic it costs about ten dollars per year to run a lava lamp daily. So that's something you can share with whoever may be concerned about wasted energy.
Here's the information from the GE Reveal bulb.
Lighting Facts Per Bulb
Estimated Yearly Energy Cost $4.82
Based on 3 hrs/day, 11¢/kWh
Cost depends on rates and use
Based on 3 hrs/day
So I decided to run the figures for me in the UK
4 x astro lamps, on roughly 10 hrs a day
Works out to £84 a year, or roughly $117.
£21/year for an astro (running 10 hours a day)
Quite depressing really!
I need some solar panels...