Comment 5 for bug 924278

I think the root of the problem is that if xscreensaver is built with DPMS support, there doesn't seem to be any setting to make it just leave DPMS alone. Also, we probably need the DPMS support because it allows xscreensaver to conserve resources when DPMS turns off the monitor.

So as it stands now, if you are using xscreensaver you must use the DPMS settings provided within xscreensaver. Any attempt to use other tools (xset) will fail because xscreensaver will override the other tool.

Within xscreensaver preferences under the Advanced tab you can change DPMS settings.

Works for me on Saucy, xscreensaver Version: 5.15-3ubuntu1