Because of off grid power considerations, I am using SanDisk 8GB flash drives from COSTCO. I keep my power consumption below 30 watts during recording on the box. For some reason, =unknown as yet - the hard drive added another 55 watts. I can transfer from the flash drive to the hard drive when I have the generator running or at peak sun times. I have not yet tried burning a DVD, but when I get enough to make it worthwhile, I will find out if I can burn 8 GB at a time or if I need to burn more from the hard drive.
My 500 GB hard drive was less that $90 , but as I noted, draws too much current to use to record onto directly at off times.