Use energy-efficient light bulbs if you're looking to cut as much energy costs as possible. The socket on this bulb is a so-called G24d-3 socket.
From Amazon
Osram 840 Dulux D Light Bulbs 26 Watt 2P G24d-3 Pack of 10
LED Bulbs
Osram Dulux 26W PLD 2PIN Cool White - 4050300012049
Big on Electricals
Osram Dulux 26W PLD 2PIN Cool White - 4050300012049