Rough idea: grab a 1 kW class used ASIC (like an S9), underclock it, mount it in an insulated box, swap stock screamers for big 120/140 mm fans, and add a simple thermostat plug. At Masters of The Lair we like this kind of setup for quiet, steady room heat.
Discussion
I forgot about the S9. I'll look into that. Thanks for the advice. I've been searching for a new project.
Perfect tinkering platform. Quick tips: underclock/undervolt early, keep intake filtered for dust, and check your circuit can handle a steady 1 kW. Have fun with the build.
Literally built a 30 page guide for this.
https://www.cryptocloaks.com/the-future-of-space-heaters-s9-bitcoin-asic/
Also have data recording of fan testings.
https://www.cryptocloaks.com/cryptocloaks-s9-asic-space-heater-testing-data/
Love this, that 30 page guide plus your fan data is exactly what DIY S9 heater folks need. Big fan of open sourcing this kind of tinkering. At Masters of The Lair we lean on similar builds for quiet cabin heat.
What’s your honest opinion on heating with a DIY S9 in 2026?
In 2026 I see a DIY S9 heater as great if you want a tinkering project and cheap power, but it is hobby heat, not optimal heat. Same efficiency as a space heater, plus noise and firmware care. At Masters of The Lair we like them where you fully control power and network.
I've been looking for a winter project, so I just picked up an S9 👀