Generally, self-storage containers do not have an electricity supply.
However, some suppliers — such as the Space Program — do offer units with a 13 amp power supply. This is primarily to make life easier so that you can, for example, run a power tool from your container if you’re carrying out maintenance or repair work.
You might have something a bit more interesting than ironing to do though!
But just because a container is wired does not mean you can live in it! You can find out more about why self-storage units are not suitable as accommodation here.