What are energy efficient light bulbs?

A Low energy bulbs uses about 1/5 energy of a traditional bulb.

ie. 20w (Low energy bulb) = 100w (standard filiment bulb)

80%+ traditional bulb s' energy is lost as heat.

The 20% figure shown above only relates to the low energy bulb during its normal usage. The question was about the overall ecological balance, which includes ecological burden through manufacture, distribution and disposal (or recycling). Low energy light bulbs contain heavy metals, electronics and toxic materials, and are manufactured (and recycled) using much more complicated and, presumably, more ecologically damaging processes compared to those involved in traditional tungsten filaments.

The question is still open thus.