When booting up CRS310 starts at 10W, but then when it boots up to rOS, it goes all the way up to 15W at the wall and stays there. That’s a lot for a switch that is doing nothing and has nothing connected to it.
If I had to guess the extra 5W is the NIC/phy that gets initialized once booted up and 10W is the CPU itself. Maybe it would be possible to enable frequency scaling on the CPU or something to bring its consumption down at least somewhat?
Thank you!
Product page says that max power consumption without attachments (e.g. without SFP+ modules inserted) can be up to 21W. So what you see is definitely inside expected values. I highly doubt that any (noteworthy) power consumption reduction is possible by changes in software.
I checked a random Taiwanese 8-port 2.5Gbps switch (so no SFP+ ports, no L3 functionality) and it’s rated at 8.something W. If you consider 15-21W to be too much for a highly-manageable switch with decent routing capabilities (using L3HW offload), then you may want to reconsider your purchasing decission.
Product page says that max power consumption without attachments <…> then you may want to reconsider your purchasing decission.
Of course it does. I’m not saying that I was misled or anything of the sort. I also can’t really consider alternatives. I’m proverbially locked into rOS and figuring out how to click buttons on a web interface is going to be more expensive than the power this device will consume over its lifetime ^^
That doesn’t mean I can’t suggest ways to improve the product. I also suggested a concrete software-only approach to explore. Even if that doesn’t pan out for this switch, maybe that informs future product design? Who knows! Though ultimately, in my experience developing products, its always going to come down to some software tunable that is tuned wrong by default 
As another comparison point I do want to point out that a full blown N100-based router/firewall with 4xI226 and a dual port 82599ES based SFP cages can fit into 10W (with some attachments and goes down to 5-6W with the ancient SFP card taken out.) And this is a device built out of general purpose parts, some of which are old and have poor track record in terms of their power consumption.
UPDATE (06-03): I ended up deploying a trusty CRS317 with SFP-RJ45 thingies instead. The power consumption ends up roughly the same for the similar number of attachments, but CRS317 has more ports & a straightforward incremental upgrade path to 10GbE, as needed. The only reason to go for CRS310 I can see is if the budget in this weird place where there’s enough for CRS310, the exact port configuration is locked-in and closely matches what CRS310 provides…