How efficient is 'sleep'?

[Backwoods BC]

I have quite a few "service-like" scripts that I put into the
background and then have them wake up on a regular basis to do
something. I use 'sleep' for the timing of the wakeup periods.

My question is: How efficient is 'sleep'? I know of other OSes that
just set a timer flag and the process isn't allocated any CPU time
until the timer expires.

I know that creating a service or even using Task Scheduler are more
"proper" ways of doing this, but they are also much more work and
would require a significant learning curve as my background is
embedded systems, not Windows. I know that my lazy way probably has a
penalty, but just how bad is it?

Thanks