AP energy efficiency - PoE scheduling: Experiences or recommendations?

[koffi2k]

G'day

 

We're yet going live with our first wireless network on parts of our campus. At the moment we plan to go with a set of UniFi UAPs and hope to focus then on the UAP-Pro. One thing that I feel is seldom considered and I haven't found experiences on the internet is is the power draw of access points and overal energy efficiency of a wireless campus network. Maximum power draw in the specs. of UAP (4W) and UAP-Pro (12W) may not be that high, but if we expect like 100 APs spread over the campus, this could go up to (ok, theoretical) 10'000 kWh per year added to our power usage just for wireless networking.

 

Our Switches seems to be able to schedule PoE ports so this would allow to power down most of the APs outside of school hours (like 8 PM - 6 AM) plus weekends (even holidays!) where nobody will be on place using the network.

I have done some calculations and think that we could engage some considerable energy efficiency improvements (up to 50% compared to 24h uptime) if we do scheduled shut down of APs during times there is nobody on place.

 

- I'll do some testing on my own - but what are users here thinking about powering off APs on daily base?

- Will it bring more headaches compared to 24h x 365days uptime - aka: is it even worth the additionaly work?

 

Currently paying the power bill is not the issue of the IT services... but still I feel considering energy efficiency in current times should be part of such projects - not?

Edited July 27, 2012 by koffi2k

[SYNACK]

Maunal switch off of 100 APs is going to be so much of a troule causing mess that you'd be forever chasing them. Your users may be reliable but if they are anything like the species here I'd automate or just leave them on.

[psydii]

One approach would be to choose your POE switches/injectors carefully. I understand that a lot of them can't completely shut down their consumption of power even when a non POE device is connected. <-I have not verified this, nor can I recal where I read it.

 

Ultimately though, doing more takes more energy. Probably easier to offset the AP's footprint.

 

Think about your desktop PC purchases, you can save 100W's per device in some cases. That dramatically reduces the cooling requirements too.

 

Then you can look at turning off a couple of air con units. Energy saved.

[koffi2k]

Maunal switch off of 100 APs is going to be so much of a trouble causing mess that you'd be forever chasing them. [...]

The switches feature a scheduling functionality for specified ports - if things work well, it means that we'd not have to touch that configuration manually afterwards.

I wouldn't even be considering this if there was no option to do that on automated basis (even scripted) - I definitely don't want to chase after 100's of ports.

I'll have to figure out if rebooting the APs doesn't mess up the wireless network.

 

One approach would be to choose your POE switches/injectors carefully.

I understand that a lot of them can't completely shut down their consumption of power even when a non POE device is connected. <-I have not verified this, nor can I recal where I read it.

Definitely something to check out with our switches. AFAIK it should cut the power so that the AP will be powered off and re-powered when the port is scheduled to come back online.

 

Ultimately though, doing more takes more energy. Probably easier to offset the AP's footprint.

Ubiquiti's dual radios and Gbit-uplink AP seems to be drawing compareable power when, I gave a look at the Cisco 1142N (13W).

Yup, we absolutely want UAP-Pro (UAP 4W is 2.4GHz only) and real PoE without adapters if we can (48V to their 24V is also adding losses). In general I don't expect the power draw of APs to go down with future wireless standards if I'm not too pessimistic.

 

Think about your desktop PC purchases, you can save 100W's per device in some cases. That dramatically reduces the cooling requirements too.

Then you can look at turning off a couple of air con units. Energy saved.

Allas, the only air con is in the server room and "quite required", we've already taken measures where we could (or could afford with meanigful ivestments/replacements). ATM it's about measuring the expected grow in the required power budget simply because of this new network.