FreedomBoxBlog

Cheap hardware for the FreedomBox software

Rob van der Hoeven
Sat Mar 31 2012

In this article i answer the following question: When does the energy cost of running the FreedomBox software on a desktop computer justify buying specialized low power hardware? The answer to this question may surprise you.

Not long ago a reader of my blog asked me why he could not use his desktop computer to run the FreedomBox software. I answered that he could, but it would not be very economical. I gave him the following example: My desktop computer at the time consumed 93 Watt when idle. Keeping this machine running for a year would cost me 186 EUR. The energy costs of my 11 Watt NAS "FreedomBox edition" is just 22 EUR a year. In this example it is clear that it pays to buy special hardware for the FreedomBox. For my new energy efficient desktop computer (23 Watt idle) the situation is different. In a previous article Free hardware for the FreedomBox software i argued that the cheapest hardware for the FreedomBox is hardware that you need anyway. If you can run the FreedomBox software on this hardware without changing it's function, then the hardware for the FreedomBox costs you nothing. This is true for always-on devices like wireless routers and NAS servers. With these devices the only cost of running the FreedomBox software is the cost of the extra energy which is probably very low. For desktop computers the situation is different. Desktop computers consume more energy than specialized always-on devices and are only used part of a day (normally).

How much does it cost to use a desktop computer to run the FreedomBox software?

Calculating the costs is very easy. Because you need the desktop computer anyway, the price does not enter the equation. Only the extra energy costs are important. This leads to the following equation:

Cd = Pdi * Td * Ckwh/1000

where:

Cd    : Cost of running FB software on a desktop computer
Pdi   : Power consumption in Watt of the desktop computer when idle
Td    : Time in hours the desktop computer is running FB software exclusively
Ckwh  : Kilowatt-hour price.

Because the FreedomBox software is mostly sleeping, i only take the idle power consumption into account.

How much does running a dedicated FreedomBox device cost?

With a dedicated device you have to enter the price of the device into the equation:

Cf = Cfd + Pfi * Tf * Ckwh/1000

where:

Cf    : Cost of running FB software on a dedicated FB device
Cfd   : Price of the FB device
Pfi   : Power consumption in Watt of the dedicated FB device when idle
Tf    : Time in hours the FB device is running

Some quick calculations.

Let's compare the cost of my (very) energy efficient desktop computer with a DreamPlug. I use the following parameters:

Pdi  = 23 W
Td   - do not correct the time for non FB use of the desktop computer.
Cfd  = 163 EUR DreamPlug + 50 EUR USB hard-disk = 213 EUR
     - assume a 3 year life of the DreamPlug 
Pfi  = 5 W DreamPlug + 5 W USB hard-disk
Ckwh = 0.25 EUR

For a 3 year period this calculates to:

Cd = 23W * 3*365*24 * 0.25/1000           = 151 EUR
Cf = 213 EUR + 10W * 3*365*24 * 0.25/1000 = 278 EUR

In this example using a DreamPlug as a dedicated FreedomBox device is not economical. Even with no correction for the time the desktop computer is used for it's normal tasks, the DreamPlug solution is almost 2 times as expensive.

Using the DreamPlug results for a 3 year period you can calculate the idle power consumption of a desktop computer that is just as expensive as a dedicated DreamPlug. This turns out to be 42 Watt.

Let's calculate the costs of running a Raspberry Pi model B for three years.

Cfd = 39 EUR (32.70 GBP * 1.2 EUR/GBP) + 50 EUR USB HD = 89 EUR
Pfi = 1 W Raspberry Pi + 5 W USB HD = 6 W

Cf  = 89 + 6W * 3*365*24 * 0.25/1000 = 128 EUR

The very low power Raspberry Pi is the winner. It would save me 33 EUR over a period of three years. For me, this is not a good reason to buy a Raspberry Pi. (Still think i buy one, just for fun!)

(Note: in these calculations i have not corrected for the time i use my desktop computer for it's normal tasks. If i correct for the 8 hours a day i use my system for desktop-tasks, the desktop costs for running the FreedomBox software would be 100 EUR.)

Conclusion:

If you have desktop computer with low idle power consumption, then there is no (economical) need to buy special low-power hardware for running the FreedomBox software.