Are number of desktops affecting memory?

Solution 1:

Look at it in another way: You don't have 8 desktops but you just have 1 desktop. The applications are bundled into groups and only certain groups of applications are shown on your desktop screen. When another application becomes active from another group, then the selected group will become active on your desktop. It feels like your have 8 desktops but in fact you only have 1.

So to answer your question: It will need more memory than a static desktop but I doubt it's even Noticeable.

Solution 2:

Having various applications open (on the same or on different desktops/spaces) requires much more memory than the desktops/spaces themselves. Even with different background pictures on every desktop the memory impact will be low compared to whatever else is going on on your machine.