My SOHO router has a some “green” configuration features to reduce energy consumption:

• (wi-fi) A scheduler for the Wi-Fi radio to turn it off automatically during times it won’t be used. (dd-wrt has this)
• (wi-fi) A power level throttle (10%, 20% 50%, 100%) so you are not amplifying the signal beyond the range that you need. (dd-wrt has this)
• (wi-fi) A bezel button on the chassis so you can easily turn Wi-Fi on and off without entering the configs.
• (wi-fi) choose an SSID that does not feed an oil partner (details).
• (ethernet) A per-port choice of 1 Gbits/sec or 100 Mbits/sec. Apparently capping it to 100 Mbits/sec saves energy because they’re calling it a green setting. I’m a bit surprised the savings would be notable enough to justify the option. But I doubt my uplink has more than 100 Mbit/s anyway so I capped my ports.

Beyond the router:

• (uplink) Since GSM radios use 30 times more energy than a wire, obviously getting your internet over cable, dsl, or fiber are more energy efficient than GSM (and probably any wireless uplink for that matter).
• (web browsing) Disable image loading in the browser because images are much heavier than text. Most images are junk anyway.

reverse tethering

I’ve started reverse-tethering my phone over USB, so I can keep Wi-Fi disabled on both my router and devices most of the time. This option is threatened though, because the Android tool Gnirehtet is no longer maintained.

When Gnirehtet eventually dies, theoretically it’s possible to use openVPN for reverse tethering. But the ovpn project has decided to scrap the clearnet option under the naive view that there is no use-case for an unencrypted tunnel. If you can’t get cipher compatibility between your mobile device and your PC, it will not work.