Energy-saving eco lamps have their ballast already built in, which makes the costs of acquisition more tolerable in comparison with the HPS bulbs. Another advantage is the low waste heat, so that shouldn't be a problem for your environment control.
These energy-efficient bulbs can be screwed into just any socket, yet they are rather heavy. Some of the smaller reflectors and fixtures or holders might get bent. Specially designed reflector systems for energy-saving lamps are more sturdy.