> a Macbook Pro draws 30 W when in use. If in use for 6 consecutive hours, it would draw roughly 160W per day
While I do find their lifestyle fascinating, there's a nit I feel compelled to pick here. Watt is a unit of power, while watt per time is a unit of energy. If the Macbook draws 30 W and used for 6 hours, it would have consumed 180 Wh exactly. If it draws 30 W for 6 hours every day, then it would be 180 Wh per day. I have no idea how authors ended up at 160 W per day, which doesn't make sense.
And quite apart from the unit error (W should be Wh) and calculation error (30 × 6 ≠ 160), the figure of 30W is probably wildly off target. The wording implies that figure was looked up somewhere rather than found experimentally (despite the context), and 30W is vastly more than any even vaguely recent and sensibly configured laptop will use for most tasks: the true typical figure is probably a quarter to a half of that, and could be even less for some hardware: e.g. https://www.apple.com/au/macbook-pro-14-and-16/specs/ says of their current latest hardware that it has a 70Wh battery and “Up to 11 hours wireless web” and “Up to 17 hours Apple TV app movie playback”, implying that the entire system consumes about 6.4W and 4.1W (probably a bit more) for those two tasks; a 30W load would be draining the battery in 2h20m—by no means impossible, but not the typical case. In fact, for things with batteries of their own, this kind of power consumption calculation based on battery life is very convenient, generally more so than measuring at the wall (though if you’re cutting things fine, you’ll want to consider that too because of losses in the charging infrastructure).
Later in the article they mention they’re dealing with a 2010 MacBook Pro running Elementary, and yeah, that’ll definitely consume quite a bit more power than a new MacBook Pro running macOS, but I’d still be surprised if it was as much as 30W.
Huh, my memory is evidently the thing that’s wildly off target. Thinking things through more carefully, I suppose 2–3 hours of battery life was pretty common back then, and none of their batteries would have been over 100Wh. I’d have thought 2013 would be well past the worst of that, but perhaps not.
I admit that I wrote the first paragraph of that comment before realising it was that ancient a MacBook Pro that was being mentioned, but I erroneously thought my comment was still probably close enough. Not so.
> yeah, that’ll definitely consume quite a bit more power than a new MacBook Pro running macOS
Considering they're targeting (or at least ought to target) efficiency, I feel they should probably get the newer macs with the efficient M1 chips. That way they would probably be able to get more done using a given amount of power.
But then again (from what I understand) they're on a tight budget. And I read somewhere else that they're trying to reduce electronic waste. Hence they're on the old Macbook.
Here's their situation:
1. Keep using older Macbook, thereby contributing less to electronic waste. However, this consumes a lot of power.
2. Switch to the more efficient newer Macbook. However, then their older Macbook would be wasted.
You still can't meaningfully use "Watts per day" in that context (for that matter, I struggle to imagine a scenario in which it was a meaningful unit).
Given the number involved was 160, I suspect the likely unit they meant was "Watt-hours per day".
If the plant only increased its capacity once, then the calculation would be power/time * (length of time), so it wouldn't make sense to express it as a rate.
Watts per day would be used to describe the rate at which your power consumption increases (eg “as winter comes on, power used heating the boat will increase 100 watts per day”).
Watts per day could be used to describe the rate of decay of strength of a team of horses on expedition. But probably for that application you'd better use horsepower instead.
While I do find their lifestyle fascinating, there's a nit I feel compelled to pick here. Watt is a unit of power, while watt per time is a unit of energy. If the Macbook draws 30 W and used for 6 hours, it would have consumed 180 Wh exactly. If it draws 30 W for 6 hours every day, then it would be 180 Wh per day. I have no idea how authors ended up at 160 W per day, which doesn't make sense.