Topic: Heat from computer vs electric furnace (Read 2969 times)

Or just move them outside till fall again.

Wow, so I should just start mining bitcoins and get enough gpus going to heat my house with, and do it till springtime. It would be great to rig up my thermostat to control my mining rigs, and then when it gets warm enough it just shuts them down.

Mining takes on a whole new light when it is no longer wasted energy.

Once it gets warm out, I could just sell all of my equipment to someone who lives in a colder climate.

In the end, everyone that lives in Alaska should just be mining bitcoins.

I agree completely on the "feel" of heat.  Hot air blowing on your face will obviously make you feel warmer more quickly than hot air slowly circulating around the room from a couple of computers 10 feet away.

That said, my wife and I actually get too hot by the time morning runs around with a single 2x5830 rig in our bedroom and the door closed.  We've relegated to keeping the door open a bit so some of the heat can escape to the rest of the house.  This is with outside temperatures of 35-40F.  Below 30F, and we usually have to supplement the rig with the in-wall heater.

Last month's electric + water bill was $292 (of which electric was $260 or so).  I figure I'm getting around $125 worth of BTC/month for my current mining, which means the net electric cost was somewhere in the neighborhood of $135, which is darn good for us during the winter.  Usually, we break $200 in these winter months without a sweat.

I'd be curious to know more about this.  Doesn't a statement like that go against the laws of thermodynamics?  Or, are we talking molecular changes, so that energy is stored in the form of a new molecular structure in 0.0000001% of the case instead of being released as heat?

For all practical purposes, you are of course correct. However, I seem to recall from highschool some decades ago reading about irreversible deformation and iirc, not all energy was transformed in to heat. I would assume the electromigration taking place in side our chips would fall under that. I suppose its like 0.0000000001% (if that) but just curious if thats correct nonetheless?

I think everyone answered the theoretical part of this question sufficiently   The heat generated by a computer is going to be identical to a coil-based electric heater.

However.. What has not been touched on is perceived warmth.  You may be a bachelor, so this might not matter much to you... But those with wives and girlfriends will know how this works!  Assuming you have an identical power draw on both your furnace and mining rigs, I would still say you are very likely going to have to augment with the heater.

A furnace designed to create heat and move air (in theory in an efficient manner) is likely going to "feel" a lot warmer than an mining rig of the same wattage.  This is simply due to air movement and distribution throughout the house.

One thing I did was stuff my mining rigs in the furnace room, and open the cold-air return duct so they blow warm air into it.  I then set the furnace to just run the fan 24x7, even if the burner (gas here) isn't running.  End result was an extremely hot laundry room, and a slightly reduced heating bill.  I run around 6kw worth of gear, but honestly have no clue how many BTU my furnace is rated at.  I did ponder stuffing mining rigs into the cold air ducting itself (right before the burner intake) - but then realized the fire risk probably wasn't worth it!  Note to anyone contemplating this (or running wire through a heating duct) - smoke is the most hazardous part of a household fire, and putting things that burn toxic fumes into your air vent system to ensure all the fumes get quickly distributed throughout the house is an extremely poor idea.

Now, had I designed the house ground-up to be "mining rig heated" then this would be a different story!  It's very easy to neglect air distribution and simply focus on the raw math though, and modern HVAC systems are in general very efficient at taking created heat and distributing it to where it's needed.  Mining rigs not so much.

-Phil

Reverse conversion fail on my part.  1 BTU = 0.293 Wh.  So embarrassing.  Fixed.

I thought 1 kwh of resistance heating was equal to 3,412 BTU?

Where the heck to you live.  Next door to an old coal fired power plant with no pollution controls?  $0.04 is close to wholesale price where I live.

I wonder if that is accurate info.  For it to only apply to the "electric furnace" then the power company would need two meters one for the electric furnaces and one for the rest of the house.  Not saying that is impossible but it is unusual.  Not sure why the power company would care.  The lower off peak rate is because they don't have enough demand off peak and are trying to stimulate demand.  A power company interested in their bottom line wouldn't care if you were smelting aluminum off peak as long as you are doing is off peak.

If that info is accurate then you only get lower rate for power used by the furnance.  Thus while a mining rig would be just as efficient it would cost more simply because it is billed at a higher rate.  If it were me I would callback and reverify that off peak rate only applies to electric furnace.

If it DOES then replacing your resistance heating "furnace" with a high efficiency heat pump could reduce your annual heating bill by 50% to 80%.  If you also have an AC the heat pump would replace that too and likely at higher efficiency.  If your AC is more than 5 years old it could cut your cooling costs by 20%-30%.

Still even your peak rate is very cheap (if that is total cost including transmission) which partially explains why your home is still using higher cost resistance heating.

"coil type" was still confusing to me.  Made me think of heat pump compessor/evaporator coils.

To the OP:
if your heat is RESISTANCE heating (i.e. a wire has electricity flowing through it and gets hot which heats up your home) then yes your mining rig is just as efficient.  

Resistance heating = 3412 BTU of thermal energy (heat) per 1 kWh electrical power used (and billed).
Mining Rig = 3412 BTU of thermal energy (heat) per 1 kWh electrical power used (and billed).
Portable Space heater = 3412 BTU of thermal energy (heat) per 1 kWh electrical power used (and billed).

If your "electric furnace" is a heat pump they you likely are getting 2x to 3x (maybe 5x) the thermal energy (in BTUs) for the same 1kWh of electrical power.  Yes you can get more than 1 unit of heat for 1 unit of electricity.  This is possible without violating any commonly misunderstood laws because a heat pump (or AC unit) doesn't create heat (thermal energy), it moves it.

AC unit only moves heat IN ONE DIRECTION (inside house -> outside house)
Heat pump moves heat IN BOTH DIRECTIONS (depending on if you want your house warmer or cooler than ambient temp).

Still even if you have a heat pump a mining rig is superior to provide some or all of your heating needs.  Mining rig provides both heat AND cashflow.  Unless your mining rig provides 100% of your heating needs you might want to look into replacing your resistance heating w/ a heat pump. It can cut your heating costs in half (or more).

Resistance electric heating (coil type) is very expensive to run.  A heat pump uses about 1/3 the electricity for the same heat unless you are pretty far north.  There are now window AC units with true heat pumps in them for under $1000.  They may pay for themselves in one heating season. 

Please stop using the "word" wattage.  It is like fingernails on a blackboard to us electrical engineers.

Power not "Wattage" is measured in kilowatts
Energy is measured in kilowatt-hours
Current not "Amperage" is measured in Amps
Resistance not "Ohmage" is measured in Ohms

Now we do make one exception, electric or electrostatic potential, electric potential difference or electromotive force is measured in Volts, but that is to hard to say so we do call it Voltage.

For any given load the power factor gives the ratio of resistive to reactive load.  For residential customers the utility only charges for the resistive portion of the load, large commercial consumers are charged for both their resistive and reactive loads.

As stated above the power factor of the average computer is very close to a totally resistive load.  The power factor of a totally resistive load like an electric heater is, well, totally resistive.

So if your computer consumes 1000 Watts of power and your hairdryer consumes 1000 Watts of power and you run them both for one hour you would be charged for 1 kilowatt-hour of energy for each.

My point was to poke fun at the previous poster who's electricity is leaking onto the interwebs.  Otherwise, we're using the same math.

I fully understand that wattage is a measure of the current drawn at a particular voltage, ala Watt's law:

P (work, or watts)  = I (current) * V (voltage)

But wait! Don't forget that Ohm guy, his law says:

V (voltage) = I (current) * R (resistance)

R is the only element you can normally change.  R is the light bulb, the furnace, the computer, etc, and R determines how much current you draw and how much voltage is dropped along a circuit.  You don't change current or voltage separately.


I forgot what my point was?  Oh yeah!  We're arguing from opposite sides of a balanced equation!  That's just not smart, lets not do that.

[edit] I see, when I said "The same current flows through your light bulbs, but doesn't cost as much since you use less of it as work" I didn't mean to use 'current', but instead 'electric energy' like the last guy.  Typo, my bad.

You must use different math than the rest of the world.  You should probably refrain from answering questions that involve any type of electronic circuit.

Watts = Amps * Volts... You pay per KiloWattHour, which is 1000 Watts for 1 Hour.

You can't control volts - here in the US, for example, we get roughly 110 or 220 for residential service.  Thus, the only thing you can control is current.  With volts being non-variable, the only thing you can use to control Watts is Amps (Current), thus, you effectively pay for Amps.

a lightbulb pulling RMS Current of 1 Amp is EXACTLY the same as a Computer Power Supply pulling RMS 1 Amp (assuming it has a high PF) from the electric meter's point of view.

Enigma

And perhaps somebody is steaing your water! Watch out!

Electricity cost is calculated on wattage used as work (eg. producing heat), not current flow.  The same current flows through your light bulbs, but doesn't cost as much since you use less of it as work.

In practical situation, it is likely that they are extremely close to each other. In the OP situation, it asks for the electric cost which is the incoming energy to the house. It is possible that the electric energy go out from other wires such as the Internet wire.

I called my electric company to see how their rates work. I'm paying $.039 per KWH off peak and $.081 per KWH on peak. The off peak rate only applies to the furnace when the power company is at low demand. So I still have to be careful about leaving lights and appliances on.

It's a coil type.

I wish I had thought of this before. Now I can leave on all the lights and appliances I want.

  Which is percisely why I asked and electric furnace is in quotes.

No it isn't.  The heat coming from the computer is exactly the same per kWh as from a electric furnace.

You may argue that some of the power is wasted as sound waves, but even the sound waves will get absorbed by the walls and get converted to thermal energy.  Moving air will collide with stationary air and generate heat as the flow calms down.  Even the light from LEDs will get absorbed by the surface it hits and converted to heat.  Every single milliwatt used by the computer is converted to heat.

The calculation is different for a heat pump (inverted AC), but a heat pump is not an electric furnace.