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> During the winter time the GPU also doubles as a 300W in-house heater. Just a reminder that heat pumps can consume 300W of electricity to provide 1200W of he

> During the winter time the GPU also doubles as a 300W in-house heater. Just a reminder that heat pumps can consume 300W of electricity to provide 1200W of heat.

sva_ 18d ago
Under ideal conditions with outside temperatures* But yes
stymaar 18d ago
Of course, but the power dissipated in a data center provide zero heat for your house. (Tangent: I wonder why we haven't seen deployment of organic Rankin cycle generators in AI data centers, the exhaust temperature should be compatible and that could yield a 10-20% energy bill saving).
- mattmanser 18d ago
  I have no idea what they use, but Stockholm is already using the waste heat from data centres: https://eu-mayors.ec.europa.eu/en/news/stockholm-sweden-heat-recovery-data-centres https://eu-mayors.ec.europa.eu/en/news/stockholm-sweden-heat...
  - stymaar 18d ago
    They use it in the city heating system, which is obviously the optimal way of reusing the heat but most data centers aren't put next to such a heating system. I'm talking about making electricity back from the heat (using a low-temp thermodynamic cycle). It has a low yield (due to the low input temperature) but it's usually economically viable when using heat that would end up in the heavens anyway.
    - adgjlsfhk1 18d ago
      the heat is way too low grade. typical water cooling setups only have ~50C water. that's barely anything
- jonas21 18d ago
  That's also true in the summer when you don't want that heat dissipated in your house.
  - hunter2_ 18d ago
    Easier said than done, but if you water-cool the GPU just upstream of your domestic water heater, it wouldn't be a bad thing. Perhaps using coolant and a counterflow heat exchanger, rather than the potable water, but the point stands. Would just need a secondary tank as a buffer (able to soak up heat from the GPU at all times, even when there's no demand for hot water) which then flushes in when demand exists.
    - zrail 18d ago
      Let's say your GPU uses a constant 300W. It takes approximately 1.16 Wh to heat a liter of water 1 degree celsius under 100% efficiency. This setup won't be 100% efficient, so let's round up to 1.5 Wh per liter per degree (roughly 80% efficient). A typical domestic water heater in the US 40-50 gallons, so roughly 160 liters. Let's say your incoming water temperature is 18C and you want it preheated to 50C, which is 32C degree differential, which means you'll need 32 * 1.5 * 160 = 7680 Wh, or 25 hours straight to heat the buffer tank from scratch. You'll need to purchase a small water-to-water heat exchanger ($50), two pumps ($100 each), a power supply for said pumps, hose and/or copper pipe and fittings, and various other sundries, plus the cost of a buffer tank ($600ish), so figure all in roughly $1000, plus the cost of electricity to run the pumps. At $0.22/kWh you're saving roughly $450 a year with this setup in foregone water heating, but because it's not 100% efficient you're spending $500 in electricity to run your GPU 24/7/365, and that's the maximum you can possibly save with the above assumptions. Scale up for more GPUs and down accordingly for less usage as you see fit. Alternatively, use air as the heat conductor by placing the GPU laden machine in the same space as a hybrid heat pump water heater.
      - fc417fc802 18d ago
        Just recycle an old water heater as the tank? I think your cost estimate is way overblown but it would certainly eat up a lot of time and effort to DIY. Regardless there's a much bigger flaw with this plan. Water tanks need to be kept above or below certain temperatures. The "preheated" range being described here is distinctly unsafe due to various microorganisms IIUC.
- MisterTea 18d ago
  > I wonder why we haven't seen deployment of organic Rankin cycle generators in AI data centers Because there was never a long term plan for AI data centers. It's an AI market capture and cash grab scheme that ends when local models eat their lunch.
  - drivebyhooting 18d ago
    That makes no sense. Do you think their plan is to spend billions of dollars and build infrastructure mega projects just to let it sit idle? Did the rise personal computing make data centers and super computers obsolete? Any advance in inference that allows local models to do the job will also benefit hyperscalers. Imagine the sheer amount of compute they could throw at problems if each 32GB of VRAM was enough for frontier reasoning.
    - perfectbeeing 18d ago
      CCC was building the Cray-3/SSS when it went into Chapter 11 bankruptcy in March 1995.
    - AngryData 18d ago
      They could also be betting that there will only be 1 or 2 big winners. And if they don't win they are saving on expenses, if they do win then they will have all the money they need to upgrade later if they want.

> During the winter time the GPU also doubles as a 300W in-house heater. Just a reminder that heat pumps can consume 300W of electricity to provide 1200W of heat.

sva_ 18d ago

Under ideal conditions with outside temperatures* But yes

stymaar 18d ago

Of course, but the power dissipated in a data center provide zero heat for your house. (Tangent: I wonder why we haven't seen deployment of organic Rankin cycle generators in AI data centers, the exhaust temperature should be compatible and that could yield a 10-20% energy bill saving).

mattmanser 18d ago
I have no idea what they use, but Stockholm is already using the waste heat from data centres: https://eu-mayors.ec.europa.eu/en/news/stockholm-sweden-heat-recovery-data-centres https://eu-mayors.ec.europa.eu/en/news/stockholm-sweden-heat...
- stymaar 18d ago
  They use it in the city heating system, which is obviously the optimal way of reusing the heat but most data centers aren't put next to such a heating system. I'm talking about making electricity back from the heat (using a low-temp thermodynamic cycle). It has a low yield (due to the low input temperature) but it's usually economically viable when using heat that would end up in the heavens anyway.
  - adgjlsfhk1 18d ago
    the heat is way too low grade. typical water cooling setups only have ~50C water. that's barely anything
jonas21 18d ago
That's also true in the summer when you don't want that heat dissipated in your house.
- hunter2_ 18d ago
  Easier said than done, but if you water-cool the GPU just upstream of your domestic water heater, it wouldn't be a bad thing. Perhaps using coolant and a counterflow heat exchanger, rather than the potable water, but the point stands. Would just need a secondary tank as a buffer (able to soak up heat from the GPU at all times, even when there's no demand for hot water) which then flushes in when demand exists.
  - zrail 18d ago
    Let's say your GPU uses a constant 300W. It takes approximately 1.16 Wh to heat a liter of water 1 degree celsius under 100% efficiency. This setup won't be 100% efficient, so let's round up to 1.5 Wh per liter per degree (roughly 80% efficient). A typical domestic water heater in the US 40-50 gallons, so roughly 160 liters. Let's say your incoming water temperature is 18C and you want it preheated to 50C, which is 32C degree differential, which means you'll need 32 * 1.5 * 160 = 7680 Wh, or 25 hours straight to heat the buffer tank from scratch. You'll need to purchase a small water-to-water heat exchanger ($50), two pumps ($100 each), a power supply for said pumps, hose and/or copper pipe and fittings, and various other sundries, plus the cost of a buffer tank ($600ish), so figure all in roughly $1000, plus the cost of electricity to run the pumps. At $0.22/kWh you're saving roughly $450 a year with this setup in foregone water heating, but because it's not 100% efficient you're spending $500 in electricity to run your GPU 24/7/365, and that's the maximum you can possibly save with the above assumptions. Scale up for more GPUs and down accordingly for less usage as you see fit. Alternatively, use air as the heat conductor by placing the GPU laden machine in the same space as a hybrid heat pump water heater.
    - fc417fc802 18d ago
      Just recycle an old water heater as the tank? I think your cost estimate is way overblown but it would certainly eat up a lot of time and effort to DIY. Regardless there's a much bigger flaw with this plan. Water tanks need to be kept above or below certain temperatures. The "preheated" range being described here is distinctly unsafe due to various microorganisms IIUC.
MisterTea 18d ago
> I wonder why we haven't seen deployment of organic Rankin cycle generators in AI data centers Because there was never a long term plan for AI data centers. It's an AI market capture and cash grab scheme that ends when local models eat their lunch.
- drivebyhooting 18d ago
  That makes no sense. Do you think their plan is to spend billions of dollars and build infrastructure mega projects just to let it sit idle? Did the rise personal computing make data centers and super computers obsolete? Any advance in inference that allows local models to do the job will also benefit hyperscalers. Imagine the sheer amount of compute they could throw at problems if each 32GB of VRAM was enough for frontier reasoning.
  - perfectbeeing 18d ago
    CCC was building the Cray-3/SSS when it went into Chapter 11 bankruptcy in March 1995.
  - AngryData 18d ago
    They could also be betting that there will only be 1 or 2 big winners. And if they don't win they are saving on expenses, if they do win then they will have all the money they need to upgrade later if they want.