So, figure the drives are mostly idle, but spinning, you would be $4/year for the 3.5" and $1/year for the 2.5", but you might need twice as many of the 2.5" drives to get the storage if you really need 2TB, but if you don't, then it will be 10 years to recover the savings on electric, but that is your own fault for not figuring out how to spin down your drives, and not understanding opportunity cost, you can invest that $30 you saved and make $1.5/year forever, even after your drives detect the end of their warranty and fail in 3 years.
[1] Don't buy this drive. Something went horribly wrong in WD QC land. 1/3 of these that I bought failed their S.M.A.R.T. conveyance tests right out of the box and more failed in the first few months. The reviews at NewEgg suggest this is not an isolated experience. But, they are the ones I'm saddled with and know their data. Mine live out their lives happily spun down but for a few minutes a day and are closely monitored and mirrored, so their admittedly high risk of failure is acceptable.
Says 11.2ct/kWh in the US per 2011 (close enough to the $0.12/kWh cited elsewhere in this thread).
$/kWh $/W year
--------------------------------
USA 11.20 0.98
Germany 30.66 2.69
Belgium 11.43 1.00
Netherlands 34.70 3.04
UK 18.59 1.63
You can calculate prices for other countries by looking it up on the table on Wikipedia and using Google Calculator to convert to dollar per Watt year:
Additionally, I propose that we redefine the name for the unit of "dollar per Watt year" as one Belgium.
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Aside: is Wolfram Alpha ever useful for anything? Every once in a while I think of a question that would be perfect for WA to answer, and every time it disappoints me and I have to get the data from Wikipedia or Google, when WA could have also done the cost-per-year conversion for me straight away. This time it failed because as soon as you mention "energy price" WA assumes "US energy price" and tells me it has "no data" for the US energy price in Europe (which is technically correct, of course).
The variation is amazing. While most of the prices are around the average you mention, some are quite low, with a decent number of people paying under 4 cents/kWh. On the other side of things, on place in Alaska pays over 100 cents/kWh, and a lot of others are well above the highest figure on your table. For somebody who buys power from the Middle Kuskokwim Elec Coop Inc, 1W costs $9/year.
For what it's worth, your figures for the power draw of the WD20EARs seem to be too low -- Storage Review% measures R/W 6.5W-7.1W, idle 6.3W (odd) -- while the 2.5in drive figures are about right, but maybe a bit on the high side.
And your rule of thumb for energy prices doesn't work in Germany (and possibly other countries), where 1W of electricity for one year will go for about USD 2.50, if not more.
The numbers I used are from WD's spec sheet. The Storage Review discrepancy is too large to easily explain. Either something is wrong with that test, or WD has posted fictitious numbers.
The $1/year/watt rule is for the United States with a $0.12/kwHr cost. Even in the US the cost varies wildly, but just getting people within one order a magnitude on their electricity reasoning is worthwhile.
I had no idea German electric rates were so high, but it does help explain why large solar power projects are feasible there despite the less than exciting insolation.
I agree that the discrepancy is unusually high. The idle power consumption for other drives reviewed by them is lower and more in line with expectations.
Everything is more expensive in Germany, energy in particular. A rather high VAT (19%) in addition to taxes specific to energy, including gasoline and eletricity, cause this. Part of this is due to a conscious political decision to encourage energy conservation and investment into renewable energy; in fact, of the 0.2 EUR/kWh, about 0.03 EUR are a flat tax/allocation towards renewable energy. This has spurred photovoltaics, but particularly wind energy, which in 2010 accounted for 6.2% of the total electricity.
Powering a 3.5" disk drive costs about $4/year.
Remember the rule of thumb: Each watt that you run all year long costs you $1/year in electricity.
(Also, Backblaze drives probably spend most of their time spun down and thus use nearly no electricity.)
EOM
Some data:
So, figure the drives are mostly idle, but spinning, you would be $4/year for the 3.5" and $1/year for the 2.5", but you might need twice as many of the 2.5" drives to get the storage if you really need 2TB, but if you don't, then it will be 10 years to recover the savings on electric, but that is your own fault for not figuring out how to spin down your drives, and not understanding opportunity cost, you can invest that $30 you saved and make $1.5/year forever, even after your drives detect the end of their warranty and fail in 3 years.[1] Don't buy this drive. Something went horribly wrong in WD QC land. 1/3 of these that I bought failed their S.M.A.R.T. conveyance tests right out of the box and more failed in the first few months. The reviews at NewEgg suggest this is not an isolated experience. But, they are the ones I'm saddled with and know their data. Mine live out their lives happily spun down but for a few minutes a day and are closely monitored and mirrored, so their admittedly high risk of failure is acceptable.