for render time... I went pretty easy in the past... I would just charge that out at $10/hr... easily making profit compared to the electricity needed to run the machines... but I also have seperate computers for rendering so it did not impact my hands on work time.
If rendering causes you to not be able to use the computer... charge a bit more.

I would also highlite that low charge as a way to make the clients feel good about the bill...

Mike Fitz
www.3dartz.com

I charge my full rate for everything including render time as I only use one computer and the CAD/Render program is not available for other jobs at the time. I should note though that most of my renders are fairly quick, none of those hour++ times one often hears about. I think if I had to have huge render times I would get a second computer for that so I could continue to work on my main computer. Then I would charge half my rate for rendering time on any render heavy work, since I would still need to cover the cost of the other computer, power, etc.

My instinct tells me to go low ($25 per animation) so they will want more. My labor is next to nothing so if they want four different anis I make $100.