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Hmmm. Truth.


( 4 comments — Leave a comment )
Jul. 22nd, 2008 03:30 pm (UTC)
I definitely agree with him about the whole driving slower thing, but his logic seems to be a little faulty. He looks at his idea, applies it to the whole country, and comes up with impressive and scary figures, completely neglecting to do the same, and thus downplaying, the initial idea he rejected (the whole "turning off your appliances not in use" thing) in the beginning. Sure, it may save all of 10p a day, but apply that same amount to everyone. Everywhere. That adds up. Sure, not as quickly as the cost of driving quickly, but it's still something to consider.

Driving slower is a better way to save on energy and costs, but... I dunno, I just don't like the way he completely seems to disregard other smaller steps because they're smaller steps. Like the small steps don't make a difference, only the running leaps.
Jul. 22nd, 2008 04:01 pm (UTC)
He's also basing it on motorway driving - being able to go along consistently at that sort of speed is more efficient anyway, even if the peak's at 60 not 85. It's stop-start city driving that's the problem (or crawling along in traffic jams on the motorway). How much of the driving's taking place on motorways as opposed to non-freeflowing roads? I'd be surprised if most of it *wasn't* in cities.
Jul. 23rd, 2008 12:47 pm (UTC)
I can't be bothered to do the sums again, but 10p is about a two hundred and fiftieth of what I saved. So scaled up, the nation as a whole would save on the order of a two hundred and fiftieth of what I calculated.

You can save over a two hundred and fiftieth of your fuel costs by driving *one* mile per hour slower.

Consequently, I conclude that anyone who evangelises unplugging our phone chargers is either an unthinking sheep, an innumerate fool, or is deliberately misleading people. I can assure you, it would be far easier to convince people to drive 1 mph slower than to convince them to unplug everything when they leave the house. Consequently that's what they should be doing.

Yes, I used motorway data. The savings will be less *proportionately* for those who mostly drive in towns (but those people should be using public transport or walking or using a bike anyway, both of which will save far more than unplugging wall-warts) but will be a lot more in total for people who drive more than I do. And bear in mind I drive just once or twice a month. Most people with cars drive a lot more than that.

I don't disregard smaller steps. eg, I do turn off computer monitors at home instead of just leaving the screen saver to run. I just disregard steps that are so small as to be lost in the noise. Turning off all your little devices religously will save *so* little energy as to be utterly irrelevant. You might as well ask people to eat salad once a year "to save the planet".

Now that I've actually measured the power draw of my phone charger when it's not in use (less than 0.1W, which is the lowest my meter would read, so let's assume 0.1W) that comes to about 3MJ in a year. My shower uses that much energy in under 20 minutes. Or assuming a perfectly efficient kettle which doesn't leak any heat at all, that's about the same as the energy required to boil the water for 40 cups of tea. A real kettle is maybe 50% efficient, so that's really 20 cups of tea, or about what I drink in three days. So I stand by my figures.
Jul. 24th, 2008 01:24 pm (UTC)
In the US, they're discussing dropping the national speed limit back down to 55mph.

I'm personally against that both on principal[0] and practical[1].

[0] I don't believe it's the governments job to limit speed on the basis of fuel consumption. That should be the job of the free market (which seems to be doing a great job right now. I guarantee more people are buying small efficient cars here due to gas prices more than any tax credit they could have given.
[1] In the last 4 months I have driven two trips over 1200 miles each. That 75mph to 55mph is about 11.5 hours or 60 gallons[2] verses 52, an extra 8 gallons or $32 or 16ukp. I'll happily pay the money to not have to drive that extra 12 hours.
[2] Assuming 46mpg dropping to 40mpg which is an estimate for my prius.
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Nat S Ford
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