Yearly running cost per RasbPi

16 posts
by audigex » Fri Sep 21, 2012 11:32 pm
Hey guys

Just checking some numbers to work out how much a RasbPi costs per year in electricity. I'm basically looking for the worst case scenario (most expensive electricity tariff, 100% usage, 24/7/365) to check that I'm okay with running 1 (or more) RasbPi's.

So my maths is thus:

[*]RasbPi uses 5W maximum (5Vx1A=5W, although in theory it shouldn't go higher than 700mA and therefore 3.5W, I'm looking for worst-case and I've read that the Pi will shut down at 1A)
[*]At this rate it would take 200 hours to use 1kWh (1000Wh/5W = 200h)
[*]There are 8766 hours in most years, 8790 in a leap year
[*]Therefore the RasbPi, at this loading, would use 43.95 kWh per year (8790h/200hours per kilowatt hour)
[*]The most expensive energy tariff in the UK I can find is just under £0.20 per kWh
[*]Therefore the maximum theoretical amount a RasbPi should ever cost in a year is (43.95kWh*£0.2) which is £8.79

Or with more conservative estimates using the same maths
[*]At 3.5W maximum
[*]285.71 hours to use 1kWh
[*]30.77 units per year
[*]13.2 pence per unit (direct debit nationwide average feb 2012)
[*]£4.06 per year running costs

That's an absolute bargain either way you look at it, but I just wanted to check I'm not doing anything daft or missing anything obvious with these numbers?
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by jamesh » Sat Sep 22, 2012 9:02 am
Looks about right.
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by khulat » Sat Sep 22, 2012 9:31 am
The only other thing you would have to factor in are things like USB Hubs, external HDDs etc, if you want/need to use them.
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by Burngate » Sat Sep 22, 2012 10:53 am
You haven't factored in your time.

I can do the gardening, or pay a guy to do that so I can play with my Pi. He charges me £50/hr, for cutting the grass and trimming the trees.
I used to charge £25/hr or £200/day. That's £50k a year.

At that price, the Pi is going to cost me more than my house.
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by MrBunsy » Sat Sep 22, 2012 11:13 am
Burngate wrote:You haven't factored in your time.

I can do the gardening, or pay a guy to do that so I can play with my Pi. He charges me £50/hr, for cutting the grass and trimming the trees.
I used to charge £25/hr or £200/day. That's £50k a year.

At that price, the Pi is going to cost me more than my house.

Couldn't you say that about anything? If you're setting it up to do a task, like a webserver, then the time is more or less just a one-off for setting it up, then you leave it be. Plus if it's your hobby, it's not something you'd ever want to pay someone else to do for you.
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by alexeames » Sat Sep 22, 2012 11:47 am
Looks about right, but the actual watts needed might be higher than the watts the Pi uses itself because of the inefficiency of converting 240V at the wall to 5V at the Pi. But, even then it shouldn't be any worse than your high tarrif estimate. I think we pay about 14p/kWh
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by audigex » Sat Sep 22, 2012 3:14 pm
Ah of course, I forgot about power draw at the wall.

If I call it 70% efficient then it would draw 7.14W

Same sums as before would make the absolute worst case scenario £12.50/year (62.76 units at 140.06 hours per kWh)

In actual use I'd expect significantly lower than this - but for my "this is the most it could ever cost" sums, £1/month to run a RasbPi isn't bad at all. (I'm assuming that routers/internet/gardening staff would be paid for anyway)
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by kaisersose1995 » Sun Sep 23, 2012 8:13 pm
I've been searching for weeks for a power switch and/or wake on lan solution. With those figures there's not really much point in ever powering it down :D
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by Lob0426 » Mon Sep 24, 2012 3:52 pm
I am seeing about 6watts total for a headless server!
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by anotherbloke » Mon Sep 24, 2012 4:35 pm
solar power is free and if you search the forums people have already done it. of course you pay extra by buying panels etc but as it is a hobby it's all part of the fun!
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by audigex » Mon Sep 24, 2012 10:58 pm
Solar Power is all well and good, but I live in Manchester which means I would be able to use it for about a week in May and probably half of July. :twisted:

I'm intending to use it as a lightweight home server, so I'd rather have a guaranteed always on (to which end I may well get one of those microUSB phone top up batteries to use as an Uninterruptible Power Supply. I just wanted to get a ballpark figure for how much a RPI costs to run so that I didn't get any nasty surprises. I knew it wasn't a lot, but it's nice to put a number on it so that I don't feel the need to turn it off when I'm running low on cash.
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by psutton » Tue Sep 25, 2012 11:28 am
You could work out a way to attach a raspberry Pi to a lawnmower and use the Pi to control the lawnmower, probably work out cheaper than paying someone to do it, plus money savedf you can buy more pis

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by zog666 » Tue Sep 25, 2012 11:51 am
I measured my Raspberry Pi to be using 3.2W on the wall using a normal USB phone charger type power supply, using a "Steplight" power consumption meter that is supposed to be fairly accurate.

Using even at an overpriced 28c per KWH it would only cost AU$8.34 per year in electricity.

heavily underclocking it only reduced the power use to 3.1W, so I put it back.
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by cnt » Wed Sep 26, 2012 5:49 am
mine uses 2W at the wall under load (gzip -c /dev/urand > /dev/null) from a fairly crummy power supply. it uses >3VA though, which makes for an awful power factor.
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by j0k3r » Wed Dec 04, 2013 4:22 pm
Been looking for costs online,

Thank you for this post, :D I dont think i will even turn off the raspberry pi now :D ..

Thanks again..
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by aTao » Wed Dec 04, 2013 4:42 pm
Some significant factors that have so far been omitted:

Quiescent power consumption and duty cycle: Its one thing to assume full use all the time, but this is almost never the case. Either factor a guess of percentage time in use or simple measure power consumption over a week or month.

Waste heat: This is a biggie, almost always overlooked and would have been the death knell for energy efficient light bulbs. Assuming the RPi is indoors. If you are heating the building then every single joule consumed should only be costed at the difference between electricity price and heating fuel cost. If on the other hand (side of the pond) you are using air conditioning to cool the room then each joule consumed by the RPi should be costed to include the air con.

Interesting fact: How much energy is wasted on indoor christmas tree lights in the UK?
Considering that it is a time of heating and the only energy that isnt converted to heat is the light that escapes through the open curtains. Then the total power that goes to waste in the UK due to christmas tree lights is about the same as a Mini doing 70mph.
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