In conditions when available energy is limited, illumination must satisfy in view of efficiency.
That means that part of light energy in relation to total energy which is spended on bulb operation must be as bigger as possible.

Rated voltage of energy save bulbs may be AC 230V, 50Hz or DC 12 V / 24V.

DC energy save bulbs are favorable for using than AC in aspect of efficiency, since they are supplying directly with battery voltage. On that way there is no extra losses of energy which causes usage of inverter like in case with AC voltage bulbs. Unfortunately, DC energy save bulbs are significantly more expensive than AC

AC energy save bulbs are using in case where elekctric installation for loads supplying is builted for AC. In that case it is not usually justified to mount special DC merge field.

AC energy save bulbs are mostly used in small systems without inverter or there where exist AC and DC loads.