Are Eco Ethernet switches Greener?

There was a recent discussion on Panbo where some people proposed that Ethernet, and more specifically using the IP protocol with a 100BASE-TX or 1000BASE-T physical layer. I am still sceptical of that for several reasons. One of them is that an IP stack rules out using small micro controllers, or requires extra hardware. This drives up the cost of the minimal hardware node. A zigbee or bluetooth based system is much more low-end friendly and has the added benefit of needing no wires.

Ethernet does have a role on-board in tying together both navigation hardware with high speed sensors, such as RADAR scanners and in enabling the interface between on-board computers, Wifi and mobile internet modems and whatever other gadgets turn up on board.

So I've taken the power meter to use again to measure what Ethernet costs us in terms of Watts. Less, much less, than I feared -- if you're careful. There is an interesting trend visible in the past year where many manufacturers are advertising green or eco friendly devices.

The devices that I tested were three "older" devices that carry no green or eco label: a Linksys WRT-54G access point with built-in 4 port 100BASE-TX Fast Ethernet switch, a newer Linksys WRT-54Gv2 access point also with a 4 port Fast Ethernet switch, a Sitecom LN-113 8 port Fast Ethernet switch. I also tested two eco 5 port Gigabit Ethernet switches from D-Link (DGS-1005D) and Netgear (GS105). I used the power adapters that came with the Gigabit switches as these were the newest and most efficient. The cable lengths were mixed: two that were about 5 m and two that were about 10-15 m.

Device	Load 0	Load 4	Load 3 + 1GB
Linksys WRT54g v7	3.0 W	4.1 W	N/A
Linksys WRT54gV2	1.9 W	2.8 W	N/A
Sitecom LN-113 v2	0.0 W	1.2 W	N/A
Netgear GS105	0.1 W	0.6 W	1.0 W
D-Link DGS-1005D	0.1 W	0.6 W	1.0 W

The test results show that four active ethernet ports will cost you 0.9 to 1.2 W per port if you use just any old ethernet switch. You can save power by using a new eco switch and tying any Gigabit capable ports to 100 MBit. A Gigabit port seems to use 0,5 W per port.

To answer my own question: Yes they are -- if you're careful to slow the ports to 100 MBit if that is fast enough for your requirements.

For our modest Ethernet network on board our new ship I'll be using the Netgear GS105 as that has a 12V supply (the D-Link has a 5 V stabilised power input) so it is easier to integrate. All ports will be run at 100 MBit speed to reduce power consumption.