Home Electricity Consumption

Something that has been bugging me for a while is not knowing how much electricity all my geeky stuff is drawing, particularly the things that are left on 24/7 i.e. my 'server shelf' and my media PC in sleep mode. Mark's recent post on his Windows Home Server blog prompted me to purchase an Owl Wireless Energy Monitor while they were on discount at B&Q. This page lists some measurements I've made to see how much electricity my house draws when 'idle' and how much the geek stuff is contributing to that.

House on idle...

OK, the Owl is a wireless remote monitor system that measures power being drawn into the house at the main electricity meter. I was uncertain as to how well the wireless connection would perform through the house as my wifi network struggles to get even a metre outside the house! I'm guessing my exterior brickwork is unusually good at blocking wifi. No problem though, the Owl's signal is fine throughout the house (my electricity meter is on the outside). The Owl gives a power reading for the house's electricity to a resolution of 10 W (0.01 kW).

Firstly I switched most things in the house (lights, TV, PCs, etc.) to 'off' to simulate the house as it is most of the time. While making these baseline measurements I noticed a significant rise in power as the fridge/freezer kicked into action for a while and then settled back down. Baseline readings as follows:

House idle (heating off, fridge/freezer inactive)	120 W
House idle (heating off, fridge/freezer active)	210 W
House idle (heating on, fridge/freezer inactive)	230 W
House idle (heating on, fridge/freezer active)	320 W

As you can see, the heating pump and fridge/freezer activity have quite a large effect on our consumption when the house is idle and these are the two systems that are regularly cycling on/off throughout each day. I'd be interested to know what the fridge/freezer's average duty cycle is...

The baseline readings above are meant to be typical and as such include the IT equipment that is on 24/7, my 'server shelf' and media PC in sleep mode. So how much are these contributing...?

'Server Shelf'

My 'server shelf' consists of the four appliances that are available to my PC network 24/7:

Linksys WAG-354G ADSL router
Buffalo Linkstation Live NAS
Linksys NSLU2 (currently a print server)
Canon Pixma MP210 printer/scanner.

The Owl method didn't prove to be a very accurate way of measuring smaller devices (it has a 10 W resolution) so I borrowed an inline power meter (with a resolution of 1 W) off a friend to get a closer look here.

Linksys WAG-354G ADSL Router	9 W
Buffalo Linkstation Live NAS	13 W
Linksys NSLU2	5 W
Canon MP210 Printer (idle)	2 W
TOTAL	29 W

Media PC

What about the media PC sat there sleeping all day? Again, good news, the difference between the PC powered off and in sleep mode was too small to measure but, as above, I'll have a more detailed look at this using an inline meter soon.

While testing this area I also made some measurements of the media PCs power consumption when on and compared this to my main desktop PC, ballpark figures as follows:

Media PC	60 - 100 W
TV (28" wide CRT)	60 - 90 W
Desktop PC	110 - 150 W
LCD monitor (each, I use two simultaneously)	50 W

Bear in mind that a PC's power consumption varies according to the load the system is under. As an example, I fired up Half Life 2 on the main PC and the power reading went up 30 W. It's difficult for me to put the inline meter on the desktop PC kit indivdually as it doesn't really fit onto my surge protector but, as I sit here typing this page, the whole rig (PC, 2 x LCD monitors, speakers and the DECT phone charger) is pulling 200W.