Answer:
the formula is efficiency = output / input × 100%
Geothermal, Wind ,Solar, and Water turbine.
I hope I helped.
If you're using the bulb as a source of light, then it's. 14/60 = 23.3% efficient.
If you're using it to heat a bird nest or a hamster cage, then it's. 46/60 = 76.7% efficient !
It just depends on your point of view, and what you consider 'useful' output.