Computer running costs
27 11 2006Having just boiled the kettle and made myself a cup of tea (using 0.04kWh at a cost of a third of a penny), I thought I’d do some more calculations while enjoying my drink.
And what better to analyse than the cost of running the computer for a year.
I have an Apple Mac G4 (933MHz), an Apple 17in Studio Display, an Epson Stylus Photo 895 printer, an Epson Perfection 1200U scanner, a pair of Yamaha speakers, a Belkin USB hub and a Vigor 2600W broadband/ethernet/wireless router.
When not in use, all but the broadband router are turned off at the wall.
When is use, only the perpiherals needed are powered up so that means the scanner, printer and speakers are usually off.
I have had the power meters connected for 434 hours now, so that should give a fair sample of the total power consumption and cost.
However, as I’ve had to plug the meters into the wall sockets and then the various multi-gang extensions in those, I don’t have individual figures for each peripheral.
Despite that, I can say that turning a peripheral off doesn’t necessarily mean that it is off!
The Yamaha speakers are an example of this. The switch may be off, the LED out and yet it still draws 2 watts. That’s because it uses a transformer that continues to draw current and the switch is on the speaker, not the transformer.
Anyway, to the figures:
- Electricity socket 1 (peripherals) - 1.64 kWh over 434 hours
- Electricity socket 2 (computer and monitor) - 32.29 kWh over 434 hours
To calculate the annual consumption, we first need to find out the power using the formula Power (kW) = Energy consumption (kWh) ÷ Time (hours):
- Socket 1 - 0.0037788 kW
- Socket 2 - 0.0744009 kW
The rounded number of hours in a year is 8765, so we multipy that by the power to give annual energy consumption:
- Socket 1 - 33.12 kWh
- Socket 2 - 652.12 kWh
- Total - 685.24 kWh
With electricity costing us £0.0888 per kWh at present, we multiply that by the annual consumption to give the annual cost:
- Socket 1 - £2.94
- Socket 2 - £57.91
- Total - £60.85
That’s £5.07 a month.
I couldn’t cut this by using the computer on three occasions a day instead of six or seven as I’d still be doing the same amount of work. I could reduce the total amount of time spent using the computer, but that would reduce my already limited communication with the outside world.
What I could do to cut the power consumption and cost further would be to replace the monitor. It’s an old cathode ray tube model and draws a whopping 148w on its own.
A similarly sized LCD screen would consume around 40w or less - that’s a 73% cut in power consumption for one appliance.
However, it would also cost more money than we have to replace the old one and I’m not convinced buying a new one is a good option given the amount of resources it would consume.
For now, I’ll sit tight but should we get a few quid at some point (ha, ha, ha) and an LCD monitor appear on ebay for the right price, then I might be tempted.
And what about the carbon dioxide emissions from my computer equipment over a year?
A quick look at the National Energy Foundation’s CO2 calculator reveals that 685.24 kWh of mains electrity results in the emission of 295kg of carbon dioxide a year.
However, we use Scottish Hydro Electric as our electricity supplier and are on their green tariff, which means that for each unit of electricity we use they put one unit of hydro-electric power into the grid.
Of course, it’s not quite that simple in practice but the emissions from my computer are going to be much less than the 295kg of CO2 that would be emitted if we were on the cheapest tariff and drawing on coal, gas and nuclear generated power.
Taking all my tests so far (kettle, TV, computer and peripherals), we’ve established a baseline annual energy consumption for those appliances of of 847.56kWh, at a cost of £84.14 and with emissions of 364kg of CO2.
I’ll be moving my tests to the refrigerator and freezer next, while considering ways of reducing the consumption I’ve already measured.
We already use only the amount of water actually needed in the kettle, turn the TV and DVD off at the wall (the video stays on for the time as we don’t have a clock and the satellite goes haywire if turned off), and turned the computer off when not in actual use.
That basically means reducing the amount of useage of all these appliances, although having water at room temperature may make a noticeable difference when boiling the kettle (at the moment it has to come up from 4C).
So watch this space…
So turning off appliances at the wall, in your opinion, does reduce the power bill Stoney.
There is an interesting corollary here mate, in that it is cheaper to use the later technology of the LCD monitor. however you found that it was less expensive to use the older tech. for your TV when you compared it with the plasma TV.
So both tech. can be of economic value ….. it does sound a little Orwellian to me, in that the average consumer may never be aware of the advantages of the various technologies.
What I’ve found so far is that there is a lot of “leakage” - appliances that appear to be off but aren’t. These aren’t the obvious culprits like televisions on standby, but things like speakers, radios and empty battery chargers.
They appear to be off, their lights and LEDs are off, but because they have internal transformers they are effectively still on. One or two watts may not sound like much, but take a dozen appliances like that and you’re looking at an annual power consumption in excess of 150 kWh, at a cost of £14 and with emissions of 65kg of CO2.
Multiply that by every household in the country and you’re talking about a lot of wasted energy.
So, if you’re not using it - turn it off at the wall. (This is good practice anyway as it helps reduce the chance of fire.)
However, one word of caution. Some appliances need to draw a small amount of power to maintain their memory and all your stored settings.
In our case, that includes the broadband router, the satellite TV box (it goes completely haywire), and an old and now defunct Sony television (which had to be retuned every time the power went off),
However, we can still turn off the hi-fi amplifiers, the tuner, the turntable, the CD player, the DVD player, all the computer equipment I mentioned and more.
As for the benefits of different technology, the key is to check the power in watts (usually on a label somewhere on the appliance). If it draws less power than your current appliance, then it may be worth the change. If not, avoid it.
And even if it is worth the change, you need to consider whether buying a new replacement is appropriate if the old one is still doing its job. In broad terms, most old appliances are worth keeping so long as they are working efficiently because they’re not consuming the resources need to make the replacement.
A key exception here is refrigerators and freezers. There have been such huge gains in their efficiency that it makes more sense to replace them than to keep them - especially if they’re more than 10 years old. Plus the old ones have ozone unfriendly gases and leaks from them are decidedly bad.
As for the average consumer, the occasional slap around the head with a dead mullet is probably called for!
Be more effective and a lot more fun with a LIVE mullet!! :O
Ah, but you’re assuming it’s a fresh dead mullet…