Whilst trying to keep our energy bill down, I have found that modern fluorescent low energy bulbs do not pass enough current to keep our security light timer switch running. This led to two choices, either change the switch, or revert to good old fashioned tungsten! These bulbs were relatively inexpensive, and they push out more light than most low energy bulbs, particularly when first switched on. They're just what I needed.
Obviously they do burn more energy, but it's a small price to pay, and no doubt in the longer term new designs will render them obsolete. Roll on LED technology, I say!