That plus a simple solar water heating system will get you going. Not just your electricity bill will drop considerably, but you will also be making a contribution to the environment.
It is necessary to decide how and when the shower will be used so as to decide the heating system, the water capacity, enclosure, and dimensions.
The DIY outdoor shower with hot water is ideal for refreshing after a sunbath or to clean up after a swim in the pool before heading indoors.
You should build it to be 9 ft by 16 ft for more comfort as you enjoy that refreshing private session. It’s advisable for drainage purposes to fix a wood deck around a foot above ground level, to allow a natural flow of the water off the bathing area.