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I've often wondered whether it's more environmentally friendly to use a desktop or a laptop.

To compare purely the electricity usage, I can of course calculate how long I leave my computer turned on, measure the electricity usage with a meter, convert the kilowatt hours to metric tons of CO2 pollution depending on my power company or source of power (my power company's website's calculator indicates about 3000KWh makes a metric ton of CO2 emissions). Desktops are clearly worse for the environment in this respect.

But there are other factors to consider, and I'm not sure how to compare them to the electricity cost. For example:

  • There are a lot of harmful and unjust mining practices involved in building a computer to get rare metals - is this impact greater for a desktop or a laptop?
  • Laptops have batteries, which are bad for the environment.
  • But desktops have more mass, and electronic waste is bad for the environment.

There may be specific situations where computers can be built from parts, often that people give away, which mitigates some of these concerns. But I don't know how to compare the environmental cost of production of any extra desktop parts / laptops that I have to buy against the difference in electricity usage. Does anyone have any insights into how to do this analysis, or can anyone point to any studies that have been done? Let's assume that the computer will get recycled at the end of its life (I don't know enough about electronics recycling to know whether there will still be any harmful materials left though).

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    Another factor is that laptops are much harder to repair. So if a part stops working often the whole thing needs to be replaced. But desktops can be kept going for longer. – aucuparia May 14 '19 at 8:33
  • This requires a full (statistical) Life-cycle assessment for both product groups. I doubt you will get more than opinions. Sorry, voted to close as too broad. Meta question – user2451 May 14 '19 at 14:23
  • @JanDoggen given the helpful answer I think this question could be salvaged with a bit of editing -- perhaps to focus more on how to analyze the problem, rather than seeking a specific answer. – LShaver♦ May 14 '19 at 16:16
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    I was looking for how to analyze the problem anyway, so I've edited the question to indicate that. Is it better now? – user2596667 May 14 '19 at 18:28
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"To compare purely the electricity usage ... Desktops are clearly worse for the environment in this respect." — That certainly used to be the case, and still often is, but only because people buy/build systems that are overpowered.

In 2019 it is possible to build a 'serious' desktop system that consumes very little power — provided you don't play the sort of games that have ridiculously high hardware/power requirements.

Passively-cooled cases, sensible CPU selection, solid state drives and integrated graphics (or efficient dGPUs) allow desktops to be constructed that consume very little power when in 'light duty' mode (i.e. most of the time), but can still deliver the goods when you need them to.

By way of example: The system I am using is currently consuming only ~30W — and that includes a 27" display. If I put all 6 cores/12 threads under 100% load (e.g. a fluid simulation), it only goes up to ~70W. If I artificially-stress it and flat-line the dGPU as well — something that never, ever happens in the real world, total power draw still only reaches ~140W. That's it. It's simply impossible to draw any more power in this system. The system that it replaced (built in 2011) idled at ~110W and flat-lined at ~450W. The new system out-performs the old one in every single way imaginable — and consumes only one-third the power.

My point is that — with a bit of thought — it is possible to build a desktop system that has 'typical' power consumption figures similar to those of laptops, whilst having power-on-demand for those times you really need it, and enjoying all of the other — life-extending — advantages (e.g. repairs, upgrades) that come with being a desktop.

Once you get desktop power consumption down, the components (and thus environmental cost) are roughly comparable between the two. At that point the most important factor becomes the lifespan of the device — how long until you need to replace it. That's a battle laptops lose by a country mile.

From a sustainability point-of-view, building an energy-efficient desktop system — that is correctly specced ('right-sized'), and can be repaired and upgraded to greatly extend its service life — is by far and away the best approach.

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  • Interesting point! I hadn't realized it's feasible to build low-power desktops these days. I guess I'm used to using old computers. I'm still wondering what to do with older, power-consuming desktops that meet my needs? Is it better to take them apart and use the appropriate parts than to keep using them? Since I play games, is it worth having one computer just for games, and a second computer for other uses for the sole purpose of reducing electricity usage? My computer uses 100W when idle (plus 25W for the monitor), and people keep giving me their old desktop computers. – user2596667 May 14 '19 at 13:04
  • "Gaming rigs" are built for performance, not efficiency, and there's no practical way to make them substantially more efficient. My new computer costs about AU$187 less per year to run — so the return on investment is quite high. I specced it to last at least 7 years, so over its life I will have saved ~$1300 — a non-trivial sum. Whilst extending the service life of your computers makes a lot of sense, keeping old gaming rigs running eventually doesn't because of high idle power consumption. Do the math for your particular situation and let the numbers guide you. – Tim May 15 '19 at 1:39
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    OK. I was looking more for an idea of the environmental cost of each option rather than the monetary cost (I've updated the original question to clarify that). However, since it may not be feasible to get an idea of the environmental cost of the production of electronics parts, estimating it from the monetary cost is probably as good an estimate as any. For me the savings are much lower, so it may only be worthwhile for a computer that gets used all day. – user2596667 May 15 '19 at 12:55
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    @user2596667: it's not only feasible but actually quite easy. The desktop I currently use was put together with at most "half an eye" on energy consumption but mainly to be used for machine learning-type calculations (no GPU for calculations, though) and office use (as opposed to gaming) 2 years ago, 2nd consideration was noise. IIRC, I also measured about 35 W in "normal light use" (plus 2 monitors that still work fine at 11 yo). I certainly think that updating some parts can go a long way. – cbeleites unhappy with SX May 24 '19 at 20:49
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    @Tim That's true. However, we can at least compare the carbon emissions. The answer by cbeleites is what I had in mind - it shows that the carbon emissions of production are of a similar order of magnitude to the emissions of electricity usage, plus production has the other issues besides carbon emissions. This tells me that it's probably worth making use of older, higher-consuming parts until they fail, even if they use more electricity. – user2596667 May 25 '19 at 12:01
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To add some numbers to the discussion, I found

  • a white paper from Fujitsu about a desktop (2018)

    • production energy usage: 6.8 GJ or 450 kg CO2 equivalent
    • use phase energy usage: 9.2 GJ or 30 - 500 kg CO2 equivalent (Norwegian vs. German electricity mix)
    • usage scenario: 5 years
      TODO: find out h per day or similar.

  • LCA of an Ecolabeled Notebook (2011)

    • use phase energy usage: 0.15 GJ over lifetime (corresponds to 10 W avg. power when on)
    • use model: 4 years office (but not as replacement for desktop: only 2.3 h on/working day), 2 years private use (5 h on/day).
    • Side note: personally, I buy office laptops that are 3 or 4 years old, possibly update/upgrade some parts (SSD, RAM). The last one lasted another ≈ 5 years until hardware failure (current one is still "new").

  • Dell Latitude E6400 (2010)

    • 4 years
    • total 320 kg CO2 equivalent, 160 production + 30 transport to customer, 160 use (EU mix). - 30 for recycling.

In any case, production energy usage is a substantial part of lifetime energy usage (both laptop and desktop). Thus enhancing life time, i.e. use as long as possible, is typically a good idea.
Note: with 50 : 50 energy usage in production and over assumed life time, if that computer is used twice as long, then a hypothetical replacement computer requiring the same amount of resources for production would need to use zero energy during usage in order to not need more energy in total.

  • salvage parts (laptop + desktop):
    e.g. old laptop HDD + external case => my cloud server storage (for RasPi)

  • some upgrades may do a lot for lasting usability and reducing power consumption.
    Example: upgrading HDD -> HDD + SSD (both for laptop and desktop) for me had 2 results:

    • increased speed (primary reason) => adding years to usable life time
    • HDD maybe needed only 1-2 times per day, most work takes place on SSD => lower power consumption

Some guesstimates:

There are a lot of harmful and unjust mining practices involved in building a computer to get rare metals - is this impact greater for a desktop or a laptop?

If comparing a "plain" office desktop (no particular fancy extra graphics card) with some case, power supply, mainboard, RAM, HDD, SSD, monitor, keyboard and mouse with a laptop:

  • the desktop system may contain a bit more electronics (due to less integration with the periphery devices), but it's probably not that much.
  • but this modular building principle means that most of these parts can be used until they (each single part) fail: failed parts can either be replaced or leftover parts used with another system easily (because they are normed across manufacturers).
    This is also the case for some of the laptop parts (SSD, HDD), but not for others (monitor, mainboard, keyboard, touchpad).

Laptops have batteries, which are bad for the environment.

  • Batteries don't last that long. As I use the laptop to work on trains etc. I may buy replacement batteries. If you use the laptop as desktop replacement, at least the replacement batteries are not necessary.

But desktops have more mass, and electronic waste is bad for the environment.

  • I don't think they contain that much more electronics. Most of the increased mass is steel case and frames. They are not that much of a concern environmentally: they last approximately forever (and have normed form factors since decades), so can easily be directly reused. If not, steel recycling is established and much easier than properly dealing with electronic waste.
    Also heavier power supply - but that may be overall more environmentally friendly if more efficient (?)

have to leave now, hope to finish this over the weekend.

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Desktops hands down:

  1. Materials used Aside from form factor, almost all of the components of a laptop could be plugged into a desktop and function as is. With that in mind however, laptop components are designed to be more power efficient and to be space saving whereas desktop components provide more 'power' for using the same amount of raw material; when considering that the energy usage is not worth mentioning when talking about RAM etc there isn't much of a difference aside from desktop components being significantly cheaper. You mentioned mass, desktops usually use steel frames which are almost 100% recyclable whereas the average laptop is made from plastics (PET, ABS etc) which are rarely recyled. Only concern with weight is transport but this is offset by the reduced need for raw materials.

  2. Re-Use and Recycling Laptop parts tend to live short lives owing to their high case temperatures (especially when most owners don't remove dust from their fans!) they are also significantly harder to re-use as most are proprietary (sizes, interfacings etc) and are often non even compatible with the same brand (Hard drives etc are an exception) whereas desktop parts can be chopped and changed as much as you have the effort for; you are right in saying that you can build 'graveyard' systems from old parts with many people building gaming PC's from parts that are on sale. Components from both types are recycled the same way however which is difficult to do (low profit and dirty work, often out-sourced to less developed countries as a cottage industry).

  3. Batteries I'll be brief, new and in-development battery technologies use virtually no rare, toxic or otherwise noteworthy materials. Lithium is in good supply, the only worry is being able to produce it at a fast-enough rate with electric cars using it all up.

  4. Energy Usage The reason I saw this is inconsequential is that the difference between power used is prettymuch pocket change unless you're running some beefy gaming computer or crypto miner, remember that batteries are never 100% efficient leading to a large amount of waste heat. With more and more sustainable sources of energy being made available the usage of a low-end computer (laptop or desktop) is simply not worth considering.

As for disposing of computers, re-use is always better than recycle: Sell it>Free on Gumtree etc or Donate it to schools etc>Scrap it yourself and sell the parts (PSUs sell well)>Depending on the facility they often just remove large components (PSU, case) and mulch all the rest (mainly PCBs) and extract all the metals used, the only value in a silicon chip is the design and assembly

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    Welcome to Sustainable Living! How do you know that the 'extra' energy that is used by desktop computers does not outweigh the disadvantages of laptops? Do you have any references to backup your claims? – THelper♦ May 14 '19 at 7:00
  • @THelper Bodies such as the EU Energy Star commission ratings give energy efficiency statistics TL:DR most laptops draw at max 60W whereas desktops commonly use around 200W. While charging losses tend to be small the main difference between laptops and desktops is the embodied Carbon (in other words the energy used to produce them) with batteries and seldom recycled laptop components requiring a long manufacturing chain; a metal desktop body will also have a similar value but just ask any PC builder how many uses they've got out their cases. Also refer back to renewable generation sources^^^ – Bobson May 14 '19 at 23:06

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