Power consumption: How much are your gadgets costing you?

With Earth Hour making us aware of the need to conserve electricity, we conduct a real-world test to see just how much our TVs, computers and other home electronics equipment costs to run.

(Give one hour back to our earth image by tammyjq41, CC2.0)

Earth Hour started out in Sydney just two years ago as a pie-in-the-sky idea, but its amazing momentum will this year see residents of 2848 cities in 84 countries switching off their lights in a show of solidarity for the cause of reducing energy consumption.

While it's only saving a trickle of electricity compared with the amount the world's cities guzzle every day of the year, the strong support for Earth Hour can only help raise awareness of the need to monitor and control electricity consumption.

The connected (and expensive) home

For those who have invested in high-tech gear for the home, the need to monitor energy consumption may well have become apparent upon receipt of the first electricity bill. Just how much consumption has increased is a subject of no small contention — estimates that gadgets on standby consume around 10 per cent of a household's power supply are often bandied about as a rule of thumb, but don't necessarily stand up to scrutiny.

Nonetheless, there is no doubt that today's connected homes are more power-hungry than ever. From plasma TVs that may be left running when nobody's watching them, to games consoles idling unplayed, media centre PCs, home media servers and external hard drives buzzing away 24/7, to computers left running when unused — there are more ways than ever for your local electricity retailer to be jumping with joy.

Even in standby mode, conventional wisdom has been that many devices suck down power; combine this with their always-on nature, and the bills rack up fast. Yet while many conservation advocates recommend turning off appliances at the switch, this doesn't work so well for computer equipment.

Hard drives and memory sticks, for example, should be disconnected by the operating system before being powered off to ensure data integrity. In homes with voice over IP services running, broadband routers must be left on all the time to ensure continuous service. And for those people streaming music or video libraries around their homes, the computer must be left on all the time. And, as many parents have found out, turning off video-game consoles without giving the kids time to save their progress will inevitably end in harsh recriminations.

All this adds up to two things: first, turning your stuff off for Earth Hour takes more than just a few casual flicks of the switch. And second, that it's helpful to know just how much power your connected home is consuming, so you can balance the inconvenience of switching off with the real value it delivers.

(Credit: David Braue)

Measuring consumption

I have a personal interest in power consumption: last year, I documented the process of setting up a home network that included a central network attached storage box on which I can store, and automatically back up, everything from documents to a music library to photos. It's working fine, but to say that I haven't noticed a rise in electricity bills would be lying.

Curious as to how much of this is related to the connected home, I purchased a specialised electrical meter (a no-name unit from Zazz.com.au that measures usage of devices plugged into it. Electrical purists out there may scoff at using such a seemingly basic meter, and there may be arguments that this task rightly required a high-end meter costing thousands of dollars — or, perhaps, not. But it's more electrical meter than I had previously.

Measuring consumption using a meter like this is easy: plug in the meter to your mains point, plug in your device to the meter, and push the button to cycle through the readings. Once we have readings, we can assign a cost to the consumption and figure out just how much that Earth Hour is going to save us.

And the winner is…

Every device in the house was unplugged, plugged into the meter, and plugged in again, and consumption measured during normal running time. Where a device had a standby mode, consumption was also measured. Results were as follows:

DeviceModeAmpsWattsConsumption in 1 hour (kWh)Cost per hour (at $0.1561 per kWh)Cost per dayCost per monthCost per year
42-inch plasma TVOperating1.483460.346$0.0540$1.2963$38.89$466.65
HDTV boxOperating0.08190.019$0.0030$0.0712$2.14$25.63
Networked PVROn0.06140.014$0.0022$0.0524$1.57$18.88
Nintendo WiiOn0.07160.016$0.0025$0.0599$1.80$21.58
Pioneer DVD recorderOn0.12280.028$0.0044$0.1049$3.15$37.76
Linksys wireless LAN routerOn0.08110.011$0.0017$0.0412$1.24$14.84
D-Link Ethernet switchOn0.04100.01$0.0016$0.0375$1.12$13.49
QNAP NASOn0.1230.023$0.0036$0.0862$2.59$31.02
Belkin ADSL2+ modemOn0.0350.005$0.0008$0.0187$0.56$6.74
Apple iMacOn0.451080.108$0.0169$0.4046$12.14$145.66
Windows PC Pentium 4On0.34900.09$0.0140$0.3372$10.12$121.38
15-inch LCD monitorOn0.11260.026$0.0041$0.0974$2.92$35.07
Uninterruptible power supplyOn / charging0.08190.019$0.0030$0.0712$2.14$25.63
Brother multi-function printerOn0.0370.007$0.0011$0.0262$0.79$9.44
LaCie external hard driveOn0.0490.009$0.0014$0.0337$1.01$12.14
Sony Vaio notebook PCOperating0.17350.035$0.0055$0.1311$3.93$47.20
Incandescent lamp [60W Mirabella] 0.23530.053$0.0083$0.1986$5.96$71.48
Energy-saving lamp (13W 240V 6400K temperature) 0.0490.009$0.0014$0.0337$1.01$12.14
Downlight 0.21500.050$0.0078$0.1873$5.62$67.44

Power factor was 100 in all cases and voltage did not vary significantly from the 240VAC ideal. Costs calculated at $0.1561 per kWh.

The results showed a few surprises. First, most of the electronics equipment really isn't sucking down that much power; networking equipment, for example, weighed in at as little as 5W for the ADSL2+ modem and 11W for the wireless router. The NAS, which has two hard drives spinning constantly, was unsurprisingly a higher consumer of electricity, chewing up the equivalent of 8.6 cents per day ($2.40 per month) of electricity. Taken together, the network components cost $5.51 per month, or just over $66 per year, to run.

Making sense of electricity

If you don't know what they mean, here's a quick summary that makes most sense if you think of your electricity supply as a river:

  • Volts is the width of the river
  • Amps is the depth of the river — eg, how much water is coursing along the riverbed at any given time
  • Power Factor reflects the efficiency of mains (AC) power transmission. A low power factor is like having big rocks on the bottom obstructing the flow of water, while the ideal — a rock-free river — is represented as a power factor of 100 per cent.
  • Watts = Volts x Amps x Power Factor, and is an overall measurement of relative power consumption. If your river had a waterfall, its wattage would reflect how much water was going over the edge at any point in time.
  • 1 kilowatt = 1000 watts

1 kilowatt-hour represents the usage of one kilowatt of energy for an hour. This is the basic unit by which electricity is charged. If you run a 100-watt electrical bulb for 10 hours, you have used 1kWh of energy. This is analogous to measuring the amount of water traversing your waterfall for an hour.

For devices that plug into the mains outlet, voltage will always be 240. Therefore, to measure consumption, we ultimately want to measure and compare the number of watts each device consumes.

The largest single consumer of power was, as predicted, the plasma TV, which chews through well over 300W or $0.05 per hour of electricity. That's the equivalent of $38.89 per month, although few families would, of course, leave their TVs running 24/7. Even with the TV going eight hours a day, however, you'd be paying about $13 per month while it's running and a further $1.57 for standby power if you put it in standby.

Adding in the other A/V components raised total lounge-room electricity consumption to $47.54 per month, although as mentioned above putting the plasma in standby mode when not used saved considerably. Running the A/V components in standby for a month would cost just $3.15, since many of the components reverted to a reported zero power consumption in standby mode.

This last finding raises an interesting counter-argument to the claims that energy-conscious consumers should turn off their TVs and other devices at the switch. The amount of power saved from this action is actually relatively insignificant: given that a single 60W lightbulb burns $5.96 worth of electricity per month, you'll make a much bigger dent in your energy consumption simply by remembering to turn off the lights. This is doubly the case if you have downlights, which typically consume 50W — which equates to 200W in an average four-light room, costing $0.03 per hour or $0.72 a day to run.

If you're serious about cutting your electricity bill, consider dimmer switches or changing to low-power illumination: a stand-alone lamp we tested, which uses a 13W 6400-kelvin high-efficiency bulb, consumes just $0.03 per day — one-sixth the cost of incandescents.

Computers were another thing entirely. While peripherals such as the printer burn almost no power, the iMac weighed in at a steady consumption rate of about 108W, although this increased to about 125W during periods of hard disk activity and other additional power draw.

Leaving the computer running 24/7 would consume $12.14 per month, or $145.66 per year in electricity; on the contrary, even just putting it into sleep mode for 16 hours a day (while you're at work and asleep) cuts the total bill to $4.57 per month.

Since sleep mode can be automatically activated whenever you haven't used the computer for a little while, that's $100 a year you really don't need to spend. This is particularly relevant for those who have set up a dedicated media centre PC in their lounge room: because it's a full-fledged computer, make sure your media centre box is automatically going into standby whenever you're not using it.

But what of Earth Hour? Turning out the network gear for an hour will save $0.0076 worth of electricity. Turning off the TV for an hour will save $0.054. Turning off the computer might save just under two cents. And you'll save $0.0083 for each light you don't burn during that hour. Flip your circuit breaker and go out for candlelight dinner, and you may save five to 10 cents' worth of electricity by taking your house off the grid completely.

It may not seem like much, and these figures suggest that home networking set-ups only marginally increase household consumption compared to that drained by today's power-hungry TVs and that perennial suspect, the incandescent light.

The multiplier effect, however, is where Earth Day really proves its worth. If Australia's 10 million households each saved five cents' worth of electricity — 0.32kWh each — that would be the equivalent of 3.2 million kWh saved — the equivalent of 13,760 tonnes of CO2. Extrapolate this to even more energy-hungry businesses here, and the much larger number of homes and businesses participating in Earth Hour, and you're not doing too badly.

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