I bought this soil saver composter.. it's basically 4 sides with a
lid, you can see the ground. The instructions says place it on
"earth". But can I place on the concrete? Does it make much
difference?

Choosing between a soil area vs concrete, the concrete is out of the
way, and it gets way more sun. The soil area is about 5 ft from my
bedroom window.

Jeremy, it depends on where you live.

In the arid country I find myself in - I dig about 8 to 10 inches down in
ground and keep the compost pile in the shade.

I'd only be making compost in the sun on concrete in a place like
Seattle.

Steve

Having the compost on the dirt ground allows worms and microbs to
enter the compost pile. If it is placed on concrete or inside a
container, add some soil.