Workstations and energy consumption

17 September 2008

With energy prices skyrocketing it has never been more important to look at how much energy your workstation eats up, writes Greg

Last week i received an electricity bill that had British Gas shareholders laughing all the way to the bank. For the past few months I’ve been working from home a lot, so expected an increase, but not a quarterly bill that tipped over three figures quite so easily. .

June, July and August is summer (allegedly, at least), so I haven’t been using central heating or lights and two cups of tea a day are hardly going to pile on the kilowatt hours. So that got me thinking, “what is chewing through all this electricity?” It has to be the very device I’m using to write this article: the humble workstation. It’s on from dawn ‘til dusk; it’s got a whopping great processor, a powerful professional graphics card and two high performance hard drives. And while Microsoft Word doesn’t exactly tax my machine, Photoshop, InDesign and CAD certainly get it all hot and bothered throughout the day.

I’ve been guilty of turning off the energy saving features in Windows, simply because it annoys me when I have to wake up my workstation

So how much power does a workstation use? Not surprisingly, it depends on the components inside, and one of the biggest consumers of energy is the CPU (Central Processing Unit). Instead of power consumption, chips are rated according to their Thermal Design Power (TDP), which is actually the amount of power the cooling system in a computer is required to dissipate.

To put this into perspective, my 3.8GHz Intel Pentium 4 has a TDP of 115W, while a modern Intel Core 2 Duo processor, which is not only faster, but features two processors, has a TDP of only 65W.

It’s not until you get into Quad Core territory that modern CPUs start to consume as much power as my 3.8GHz Pentium 4 and even then that’s only when all four cores are working flat out, which in most cases isn’t that often.

Graphics cards also do their bit in clocking up the kilowatt hours. In fact some of the most powerful cards can consume more power than CPUs. The latest Quadro FX boards from Nvidia are very power efficient at the low- to mid-range of the market, with a maximum power consumption of around 40W, but ultra high-end cards, such as the FX 5600 can consume as much as 170W when working flat out. That’s as much as a typical solar panel can produce at peak – and we’re talking Dubai, not Dublin here.

Lots of power can also be lost in getting electricity to your workstation. Older power supply units (PSUs) are much less efficient, sometimes in the realms of 60% efficient. So if the components inside your workstation need 250W, your power supply will have to draw 420W of electricity from the plug socket, giving off a whopping 170W in heat.

The good news is that modern PSUs are much more energy efficient and most manufacturers including Dell and HP fit ‘80 PLUS’ certified units as standard. The ‘80 PLUS’ logo certifies that PSUs have more than 80% energy efficiency, which means for a workstation that requires 250W, it will only draw around 310W at the socket, giving off 60W in heat. That’s a saving of 110W - a sunny day in Cornwall, by my rule of thumb measurements.

Finally, it’s also worth noting that CRTs can use up to four times as much power as a flat panel monitor of the same size. Luckily this is one area in which I do save money.

Keeping track of the power requirements of individual workstation components isn’t always top of people’s agenda when buying a workstation (unless you’re a bit of a geek, that is), but organisations such as Energy Star are there to help you out. To be honest I’ve never paid too much attention to the Energy Star 4.0 compliant sticker that appears on workstations, monitors and all sorts of other devices, but I’ve since found out you can tell a lot from the sticker. Specifically, that your machine uses less watts when idle, but also that its idle power consumption is less than half of its max power consumption.

Choosing a workstation with lower energy consumption is one thing, but you also need to make sure you don’t leave your workstation running when not in use. In the past I’ve been guilty of turning off the energy saving features in Windows, simply because it annoys me when I have to wake up my workstation after a period of inactivity, but this burns a lot of energy needlessly. You also need to remember to turn your machine off overnight!

So how does all this talk of Watts translate in to your bottom line? On the Energy Star web site there’s a neat utility that enables you to calculate exactly how much energy and money your workstation uses, according to different use patterns, etc.

( I strongly advise you to take a look at this as it reveals some really interesting figures. By my best reckoning I’m paying around £200 per year just to keep my workstation running, which would be cut to £120 per year with a more efficient machine and go below £100 with better energy management. Now think about an office with 100 workstations and you realise the true scale of things. That’s £10,000 saved each year, every year.

The Graphics and Workstation Performance Group at SPEC, an umbrella organisation which develops standard ways of measuring workstation performance, is also currently working on an industry-standard benchmark that measures power consumption in relation to performance for professional workstations. An initial benchmark is being submitted to the Environmental Protection Agency (EPA) for possible use in its V5.0 requirements for workstation Energy Star qualification.

The power benchmark will incorporate workloads for 3D graphics, as well as CPU workloads in areas such as rendering and computational fluid dynamics.

The observant among you will have noticed that I’ve not once mentioned the words ‘green’ or ‘environment’. This is quite deliberate. Reams of newsprint have been consumed by worthy debates on the benefits of low-energy lightbulbs and woolly jumpers. But this is all about bottom line cost-savings, figures that the bean counters at your company will understand.

Now, I’m no eco warrior, but I’ve got my loft insulated, I turn lights off when I’m not in the room, I walk to work (when I leave the house), I even own a hessian sack which marketing folks call an eco-shopping bag. However I am a bit shamed that I haven’t paid much attention to my workstation until now. I’m not about to throw this one out of the window quite yet, as the cost of producing and disposing of the machine is a major topic for discussion in itself, but I’ve certainly tuned my machine for better energy savings.

And when it comes to buying a new workstation I’m going to think long and hard about which processor and graphics card I really need for my job at hand. Obviously there are times when high-performance components are a necessity, but there are many lower powered components with exceptional performance/watt and finding the right balance is going to become increasingly critical in years to come, both for the environment, and for my bank balance (after paying my ridiculous British Gas bill).

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