(I posted this on Reddit initially, the user I highlighted is a Redditor.) This thread started here: https://old.reddit.com/r/DataHoarder/comments/ffnia3/dell_t5400_power_usage_with_freenas/ I'd like to thank @EchoGecko795 for his help in that thread and steering me in the right direction. # Setup FreeNAS 11.something on a Dell T5400. 1x Xeon E5410, 32GiB of memory, 2x 8TiB SATA drives, 1x SSD boot drive. This is an old piece of gear, 2007-2008ish most likely. Maybe 2009 at the newest. You can pick these up for $100-200 on ebay most of the time. I'm measuring power off of my UPS which has the NAS and then a minor load from a switch power supply (8 port Netgear). It's not a very precise setup, seems to have roughly 5 watt increments but it's not quite linear. But, should be a good ballpark, especially for my own comparison. My power usage started about 158W. I enabled SpeedStep and some throttling daemon and it might have climbed down to 153W (that's the kind of granularity it has, 158W or 153W -- not precise at all). This is all about idle use, which 98% of my NAS usage is. * 158W: Starting idle power usage * 153W: SpeedStep enabled. Powerd enabled. Slower mode was 2GHz, seemed to have little to no effect. Played around with modes and made no difference. * 153W I ordered a L5408 processor with a 40W TDP, half that of the E5410. Same 153W. * 122W removed 6 sticks of 4GiB DDR2 ECC memory. Way bigger change than I was expecting. 8GiB left and plenty for what I'm doing. * 117W removed Soundblaster card with a heatsink on it. * 76W!!!!! removed Quadro video card. No external power connectors on it, it probably dates back to when the system was made. Without the video card I did have to connect up a PS/2 keyboard and press F1 to get it to continue to boot. But, it booted. There's now no motherboard slots used. No CD drives are powered either. Not using any HDD power management (which might improve things even more). This whole thing has been shocking to me. Memory uses way, way more power than I thought it did. It makes sense, they've got heat spreaders on them and feel much warmer than the processor heatsink. The audio card might have been a few watts, enough to get it to increment down. Buying the lowest TDP Xeon I could find (that would fit) was useless and a waste of time. If it had a second processor, removing it might have been useful but I suspect not all that much. I am shocked by how much the video card was drawing idle. Just a text framebuffer. I wonder if maybe it activated additional circuity on the motherboard was was drawing the gist of it. Though I'm sure there are low power usage cards that wouldn't hike up the usage by 40W~. At 9 cents a kw/hour this is saving almost $5 a month (and costing about that much in total). I thought I might have to buy different gear (was thinking of a HP N40L microserver) to get reasonable figures, but I think this is a fairly respectable figure for the era. From here the returns are more diminishing. Maybe a FreeNAS two drive setup could get down to 30W? 40W? If you want to save money I hope this helps give you a few ideas. Again, this is on a mostly idle NAS and your mileage may vary. I was expecting the old CPU to be using the most power but it certainly doesn't. Edit: I'm a moron. I forgot to connect up the power to the harddrives on the last boot. Actual idle power usage without a video card is 91W.