Even light bulbs have an energy rating, and this one is G-rated. The socket on this bulb is a so-called 2G11 socket.
From Amazon
Osram Dulux L24W/840 Compact Florescent Bulb 24 W Cool White
LED Bulbs
Osram Dulux 24W PL-L 2G11 Cool White - 010755
Big on Electricals
Osram Dulux 24W PL-L 2G11 Cool White - 010755