[mythtv-users] Heat issues with USB ATSC tuners?

Michael T. Dean mtdean at thirdcontact.com
Thu Aug 30 23:30:51 UTC 2012


On 08/30/2012 04:09 PM, Raymond Wagner wrote:
> On 8/30/2012 15:16, rsh1k wrote:
>> Even 500ma at 5v (2.5w) is significant to me - I'm trying to build the
>> lowest power machine possible, and 7.5w for three tuners is almost as
>> much as the whole rest of the system...
>
> This all really seems like far too much ado about nothing. Unless 
> you're talking about off-the-grid operation, electricity is cheap. For 
> a piece of hardware running all day, every day, it typically comes out 
> to around $1/W/yr.

(based on the US EPA's published national average)

>   Is a couple bucks really worth all the heartache you're putting into 
> planning such a low power device?

So going from a (poorly-designed) Core 2 Duo or Core i system that 
averages an 80W draw and running it 24/7 for a year costs you ~$80.  
When you drop that to a (typical) Core 2 Duo or Core i system that 
averages a 40W draw and run it for 24/7 for a year, you've saved 
$40/yr.  So, just by choosing to not buy an inappropriate system, you 
can ensure your MythTV box costs you at most about $40/yr in electricity.

So, say that your system actually takes 7.5W and you get a magical 0W 
tuner.  That means you've saved $32.50/yr over a typical PC (a typical 
PC with lots of headroom for when you need it, BTW) by using your 
low-power solution.

Now, if instead, you take that 40W PC with lots of headroom and 
configure it to shut itself down when not in use and to wake up when 
required for recording or playback, it may draw about 40W when in use 
and 0W when not.  If you assume you'll average about 4hrs/day, that will 
cost you $6.67/yr--saving you $33.33/yr (more than you save by going to 
this 7.5W system).

So, you may think, "Well, I could have the best of both worlds--take my 
7.5W system and shut it down when not in use!"  That's actually true, 
and a good idea, but notice that if you do, you're going from $7.50/yr 
to $1.88/yr, which means you're only saving $5.62/yr for this change.  
Still worthwhile because there's no real loss for turning off the system 
when not in use, but there's not a lot left to optimize in the setup/not 
a lot of savings to be had, here.

In other words, a) the best way to save power is to shut off the system 
when not in use and b) there's a point of diminishing returns on 
reducing power, and you likely have far bigger wastes of power around 
your house you could concentrate on fixing.  :)

See, also, http://www.gossamer-threads.com/lists/mythtv/users/448321#448321

Mike


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