Choosing the right products can help save your wallet and the planet. 

 

How we tested

To backup our findings, we measured the power consumption of a range of devices from microwave ovens to plasma TVs in their various states from standby to full operation using a device called an AC power meter.

An AC power meter measures not only the actual or “real” power used by the device but it also measures the “apparent power”, the power that has to be delivered to that device in order for it work. That tells you the device’s “power factor”, a parameter that is becoming increasingly important in how power is generated and distributed by the power stations (see “what is power factor?” box for more details).

Based on these results, we gave each device a final “out of six” star rating.

Now obviously some devices use considerably more power than others – for example, a microwave oven chews through far more power than a notebook computer, so we’ve based the star-rating on average time of usage, standby and normal power operation.

Assumptions

In calculating the power costs of particular devices, we’ve had to make some assumptions. We’ve calculated costs based on the domestic electricity price of 13.882cents per kilowatt-hour. Most power providers also offer “off-peak” electricity for evening and night use. Typically, the tariffs here are between 5 and 9cents per kilowatt-hour. Businesses are typically charged a slightly higher rate for the first 300kilowatt-hours of power and a higher rate again beyond that.

So to keep our calculations to a manageable level, we’ve used the basic domestic tariff.

In calculating power requirements of battery-operated devices, we’ve calculated the watt-hour rating of the battery and multiplied that by a factor of 1.6 to get the energy required to charge that battery capacity.

By choosing products that are more economical in their energy needs, you’ll be helping to reduce the amount of electricity generation required as well as saving yourself money in power bills.

In Part 2 of this series, we look at three categories of notebook computers, printers and gaming consoles.

 

Notebook PCs – Ultraportables

PowerSaver Rating: 5.5

Ultraportable notebooks are not only light and easy to carry around, they’re also light on the environment and your wallet. We tested Sony’s tiny Vaio VGN-TX47GP 12-inch model in various states.

With the notebook off and the battery charging, it consumed 24.2-watts. Boot up into Windows desktop and the cost is 37.1-watts. By the time we through our UserBench Audio 2007 benchmark at it, the power reached 41.2-watts.

But that’s only one-third the power consumption of a typical modern home desktop PC and around 11% of the consumption of a serious gaming PC in full flight on Half-Life 2.

At this level though, even changing the screen brightness can make a significant impact on power consumption. At full brightness, our test unit consumed 36.1-watts. Drop the brightness to its lowest level and power consumption falls to 33.1-watts.

VERDICT: If want to drop your power bills, an ultraportable notebook is the ideal.

 

Notebook PCs – General use

PowerSaver Rating: 4.5

For this group, we looked at two models but it was Lenovo’s 3000 N100 that showed the most interesting results.

As with all notebook power bricks, this one consumed around 0.3-watts just having it plugged in – not even connected to the computer. Over the course of a year, that’s 2.628kWh of electricity down the chute, enough to run a 60-watt lamp for nearly two days.

When it comes to charging up the battery, the power consumption on this unit was 40.6-watts of power, which was nearly half the desktop replacement model. With N100 notebook sitting on Windows desktop and charging the battery at the same time, power draw rose to 63-watts.

By the time we cranked up UserBench Audio 2007, that consumption topped 80.1-watts, not far behind the 17-inch desktop replacement model. So while your average notebook PC consumes less power than a desktop PC, it’s not that much less.

VERDICT: Similar power needs to a desktop replacement notebook.

 

Notebook PCs – Desktop Replacement

PowerSaver Rating: 4

By the time you reach the 17-inch desktop “heavies”, you’ve basically doubled the power consumption of an ultraportable.

We tested Acer’s Aspire 9425WSMi notebook and with the notebook off but the battery charging, the unit consumed 73.7-watts. As we found with most notebooks, if the battery is completely flat, the notebook will charge the battery very slow until it reaches a specified voltage – at little as 1.5-watts – after that, it then pours on the power.

This particular notebook runs Windows Vista and with the CPU power set to 100% (the default when AC powered), we saw no change in power consumption whether the notebook was “resting” on the Windows desktop or charging through one of our UserBench benchtests. The result was the same – 85.6-watts, which is the same as a budget miniPC desktop without monitor. This “no change” wasn’t the norm on Windows XP notebooks so we wonder if Windows Vista’s power management itself may have something to do with it.

VERDICT: On average, desktop replacements use as much as twice the power of ultraportables.

 

Game consoles

PowerSaver Rating: 5 (PS2), 4.5 (Xbox), 3.5 (Xbox360), 3 (PS3)

There would be few households in Australia that didn’t have a games console of some kind but few would know how much their console would be costing, sitting in the loungeroom plugged in.

As soon as you plug in the power cable, an original Xbox begins consuming 1.8-watts, switch it on and that jumps up to 59.6-watts. Power consumption rises only marginally when you start gaming, reaching 65.2-watts.

The new Xbox360 and PlayStation 3 consoles would produce similar results in standby however when it comes to actual gaming, the latest consoles are gobbling up power like never before.

While we weren’t able to gain access to either for this story, the Xbox360 reportedly consumes between 110 and 160-watts due to its latest-generation graphics and processing engines during peak gaming.

But it’s Sony’s PS3 that is gaining awards of the wrong kind with power consumption peaking at a hefty 380-watts, or the equivalent of a 42-inch plasma TV. That makes the original Xbox’s 65.2-watts or the previous-generation PS2’s 45-watts look featherweight by comparison.

Certainly for the PS3, it will pay to ensure it is switched off or at least sent to standby. At 380-watts, you’re looking at more power than a desktop PC with two GeForce 8800 GTS cards.

VERDICT: New generation consoles are sucking power out of the wall like there’s no tomorrow.

 

Printers

Laser vs inkjet printers

PowerSaver Rating: 4.5 (Inkjet), 2.5 (Laser)

Everyone knows that laser printers are more cost effective in terms of cost per page for monochrome printing than most inkjet printers but you maybe surprised at just how much electricity your laser printer uses.

The high-voltage corona-discharge/primary charge roller mechanism laser printers use to print requires plenty of electricity.

We tested an example Lexmark E230 model in both standby and printing modes.

Whilst sitting quietly, our test unit pulled 5.9-watts but start printing and that high-voltage charge mechanism really sucks on the power cord, eating through 699.2-watts for brief periods during each page print.

By contrast, we tested a late-model Canon S800 individual ink-tank inkjet printer and even when printing, it only consumed 13.1-watts on average, pushing up to 19-watts when the paper-loading stepper motors kick in.

When in standby mode, it pulls just 1.3-watts and when powered up but not printing, the power consumption only rises to 4.9-watts, similar to that of our test laser printer.

In terms of energy efficiency in printing, inkjet printers leave laser printers for dead but for the rest of the time, the standby power consumption is very similar.

VERDICT: Inkjet printers use up to 90% less power than laser printers while printing but things are pretty much even in standby mode.

 

POWER CONSUMPTION - NOTEBOOKS & DESKTOP PCs
	STANDBY MODE
Device	Power consumption (W)	Power factor	Yearly Cost	Greenhouse gas production share per year (kg)
Notebook PCs
Acer Aspire 55WXMI notebook PC	0.3	0.011	$0.36	3.15
Sony Vaio VGN-TX47GP ultraportable	0.3	0.044	$0.36	3.15
Lenovo 3000 N100 notebook PC	0.3	0.048	$0.36	3.15
Acer Aspire 9425WSMi desktop replacement	0.4	0.015	$0.48	4.20

 

POWER CONSUMPTION - NOTEBOOKS & DESKTOP PCs
	POWERED TO WINDOWS DESKTOP
Device	Power consumption (W)	Power factor	Yearly Cost	Greenhouse gas production share per year (kg)
Notebook PCs
Acer Aspire 55WXMI notebook PC	62.2	0.841	$75.63	653.8
Sony Vaio VGN-TX47GP ultraportable	37.1	0.573	$45.11	390.0
Lenovo 3000 N100 notebook PC	63	0.575	$76.11	662.3
Acer Aspire 9425WSMi desktop replacement	85.6	0.868	$104.09	899.8

 

POWER CONSUMPTION - NOTEBOOKS & DESKTOP PCs
	FULL OPERATION
Device	Power consumption (W)	Power factor	Yearly Cost	Greenhouse gas production share per year (kg)
Notebook PCs
Acer Aspire 55WXMI notebook PC	62.2	0.841	$75.63	653.8
Sony Vaio VGN-TX47GP ultraportable	41.2	0.532	$50.10	433.1
Lenovo 3000 N100 notebook PC	80.1	0.544	$97.40	842.0
Acer Aspire 9425WSMi desktop replacement	85.6	0.868	$104.09	899.8

 

POWER CONSUMPTION - interpretive results	STANDBY MODE
Device	Power consumption (W)	Power factor	Time Usage per day (hrs)	Yearly cost	Greenhouse gas production share per year (kg)
Printers
Lexmark E230 personal laser printer	5.9	0.379	24	$7.17	62.02
Canon S800 inkjet printer	4.9	0.525	24	$5.95	51.51
Gaming Consoles
Microsoft Xbox gaming console	1.8	0.222	24	$2.18	18.92

 

POWER CONSUMPTION - interpretive results	FULL OPERATION MODE
Device	Power consumption (W)	Power factor	Time Usage per day (hrs)	Yearly cost	Greenhouse gas production share per year (kg)
Printers
Lexmark E230 personal laser printer	699.2	0.953	0.25	$8.85	76.56
Canon S800 inkjet printer	13.1	0.655	0.25	$0.16	1.43
Gaming Consoles
Microsoft Xbox gaming console	65.2	0.749	5	$16.15	142.79

 

 

TECH TERMS

AC – short for “alternating current”, the type of power delivered to your home via the power lines.

Active power factor correction – a system that uses electronic components to correct low power factor devices and improve the power factor back towards the ideal of 1.0. Many computer power supplies feature this and show improved power factor of at least 0.9 but some reach as high as 0.96.

CFLs – short for “Compact Fluorescent Lamps”, lamps that consume 75% less power than normal incandescent lamps, but have a number of problems yet to be addressed.

Gigawatt-hours – a unit of energy equivalent to one-thousand-million watts used in one hour.

Kilowatt-hours – Basic measure of power consumption over time used by power companies to work out your electricity bill. Equals 1000-watts of energy used per hour.

LED – short for “light-emitting diode”, an electronic device increasingly used for small and mid-level lighting requirements.

Power factor – the ratio of real power used by a device to the apparent power supplied to it. Ideally, all devices should have a power factor of 1.0 however power factor of less than 0.1 can be encountered in some consumer products. Purely resistive devices like stove elements and incandescent lamps have a 1.0 power factor, indicating that all power delivered is used by the device.

RFI – short for “radio-frequency interference”, produced by devices such as CFLs and heard as buzzing or noise in radio and televisions.

Standby power – The power consumed when a device is in its idle “low-power” state, a growing problem for governments around the world as the number of electronic devices with a standby state dramatically increases.

T&D losses – short for “transmission and distribution losses”, the amount of electrical energy lost in the process of sending power from the power station to your home or business.

Volt-amps – typically abbreviated as “VA”, this is the unit of measure for the apparent or delivered power of AC mains voltage.

Watts – The unit of measure for real or useable power consumed by a device. Measurement of watts in AC mains powered gear is complex but is the combination of voltage and current.